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Emerson Process Management - Emerson Electric Co. Microphone 3081 pH/ORP User's Manual

1. 111 12 9 Simulate pH Through Model 381 Sensor 112 19 1 pH Measurement 114 13 2 Measurng Electrode OIA 115 13 3 Cross Section Through the pH 115 19 4 uu uma ect one tels tne tuae cp ae ER he ERE ee vu eed 116 13 5 Origin of Liquid Junction Potential sese 116 13 6 Glass eet ede tren dere gae e cuc teeny 117 13 7 Two Point Buffer nennen nnne nennen 118 13 8 Liquid Junction Potential Mismatch a 119 14 1 Measurement Cell sessi entente nennen nnns 120 14 2 Measuring Electrode 121 14 5 Reference Electrode a 121 14 4 The Origin of Liquid Junction Potential 122 14 5 Electrode Potential 122 14 6 ORP Measurement 123 15 1 HART Communications 126 15 2 AMS Main Menu 127 MODEL 3081 pH ORP TABLE OF CONTENTS TABLE OF CONTENTS CONT D LIST OF TABLES Number Title Page 3 1 Wiring D
2. area sk a 126 15 3 AMS Communication 002000000 0 0 0 0 127 16 0 lt GEOSSARY e 128 17 0 RETURN OF MATERIAL L J J J 134 MODEL 3081 pH ORP TABLE OF CONTENTS TABLE OF CONTENTS CONT D LIST OF FIGURES Number Title Page 2 1 Model 3081 pH ORP Transmitter Exploded Drawing of Circuit Board Stack 8 2 2 Model 3081 pH ORP Transmitter Analog Board 9 2 3 Model 3081 pH ORP Transmitter CPU 10 2 4 Mounting the Model 3081 pH ORP Transmitter on a Flat Surface 11 2 5 Using the Pipe Mounting Kit to Attach the Model 3081 pH ORP Transmitter to a Pipe 12 2 6 Load Power Supply Requirements 2 20 enne 13 2 7 Power Supply Current Loop Wiring 13 3 1 Wiring and Preamplifier Configurations for pH ORP Sensors 14 3 2 Wire Functions for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 before removing BNC and terminating cable 18 3 3 Wire Functions for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 after removing BNC and terminating cable Wire Functions for Models 399 09 10 62 381pH
3. 85 11 1 eT 85 11 2 Transmitter Malnt nance re 85 11 3 Maintenance tonat erc tuer x st ue 86 11 4 ORP Sensor Maintenance ete 87 TES 88 12 0 TROUBLESHOOTING 89 12 1 Warning and Fault Messages 1 U 89 12 2 Calibration nnns nnne en 90 12 3 Troubleshooting General L nnne nen 90 12 4 Troubleshooting When a Diagnostic Message is Showing 90 12 5 Troubleshooting When No Diagnostic Message is Showing 102 12 6 Systematic 0 107 12 7 Displaying Diagnostic 110 12 8 Testing the Transmitter by Simulating 110 12 9 Factory Assistance and Repairs enne 113 MODEL 3081 pH ORP TABLE OF CONTENTS TABLE OF CONTENTS CONT D 130 pH 5 65 4 2 4 42 1 114 13 1 GONG A 114 19 2 Measuring 115 19 3 Reference uuu 115 13 4 Liquid Junction Polontlial u uu cort cete te tu tu 116 19 5
4. bF2 10 01 I Rp I 20MA 14 00 OFF tMAn 25 0 tEMP C bUFFEr Std ISO 07 00 I I I I I HoLd 21 00 IMPtC ON tC 100 3 OUtPUt Cur tIME 10 Snr I 200 I 1 1 FAULt 22 00 GFH 1500 COdE 000 PH 00 02 I dPn 0 00 GWH 1000 GWL 020 I GFL 010 l CAL 000 rEF LO I 040 000 Diag Message rFL 000 FIGURE 5 4 Menu Tree for pH MODEL 3081 pH ORP SECTION 5 0 OPERATION WITH REMOTE CONTROLLER 5 5 MENU TREE ORP The Model 3081 ORP transmitter has three menus CALIBRATE PROGRAM and DIAGNOSE Under the Calibrate and Program menus are several sub menus For example under CALIBRATE the sub menus are Std standard and tEMP AdJ temperature adjust Under each sub menu are prompts For example the Std sub menu contains the single prompt Std Other sub menus may contain more than one prompt Figure 5 5 shows the complete menu tree 5 6 DIAGNOSTIC MESSAGES ORP Whenever a warning or fault limit has been exceeded the transmitter displays diagnostic messages to aid in trou bleshooting Diagnostic messages appear in the same area as the temperature output readings in the process display Figure 5 1 The display alternates between the regular display and the diagnostic message Figure 5 5 shows the diagnostic fault messages for ORP If more th
5. ul eqni 105095 5 peBieuqns JO peuesu 3 95044 eui 02 uo 62 uo Josues oos ees SI MOH onseld poq 10suas ay Jo eui 5 EUM SECTION 3 0 MODEL 3081 pH ORP WIRING v e 9149 ees 4962 yey Jo payoys peseoeu og eBed uo penunuoo 1 6 9149 995 Buno loid ll 1001 dn Josues eui PUM 9 5 ejaer eos 68 aney 105098 seop uonoeuuoo ssooo1d yeyM 1HVHO HOSN3S 6 9142 995 8 9149 ees 3Hdiee onseld dn 10sues ou 1e Bunoefoid y Jo st JeUAA Ur p e 10 185 2 6 eigen ees 16 Jejdnoo A SECTION 3 0 WIRING MODEL 3081 pH ORP 1HVHO HOSN3S 11 6 942 eos goze dHOZE And yBiy jo Hd eu 01 2 995 aly 826 ojejdyoeq Bulsnoy ul uo Josuas JULI esoouo 2 ees 46 Jejdnoo 6 30 MODEL 3081 pH ORP SECTION 4 0 INTRINSICALLY SAFE amp EXPLOSION PROOF SECTION 4 0 INTRINSICALLY
6. essen 38 5 3 Menu Tree pl uuu udo NR Nose Ca eds 39 5 4 Diagnostic Messages 39 5 5 Menu Iree QRP iruin siian asas sta 40 5 6 Diagnostic Messages L 40 5 7 SIUE 41 6 0 OPERATION WITH MODEL 275 u 42 6 1 Note on Model 275 HART Communicator sse 42 6 2 Connecting the HART 4 00 nennen 42 6 3 aqp Pia ee qa 43 7 0 CALIBRATION OF pH MEASUREMENTS 48 7 1 e cie EE 48 7 2 Entering and Leaving the Calibrate Menu 48 7 3 Using the 48 7 4 Temperature Calibration 49 7 5 Auto Leo e 50 7 6 Manual iios eder au 52 7 7 Making the Transmitter Reading Match a Second pH Meter Standardization 54 MODEL 3081 pH ORP TABLE OF CONTENTS TABLE OF CONTENTS CONT D 8 0 PROGRAMMING FOR pH MEASUREMENTS 56 8 1 Errem HQ 56 8 2 Entering and Leaving the Program 56 8 3 OUTPUT Baligiigu u
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8. RID 1 RID SNS RTD SNS ART 55 RTD RIN 0 1 m RTD RIN SHIELD 2 4 20 m SHIELD EARTH GND 1 4 20 m EARTH GND Ec BM rr gt MOURE S c REI rr FIGURE 4 rss see IX wen Semssss 89985 eee 5 oss SENSOR CABLE r a 2 SENSOR CABLE NOTES 1 INSTRUMENT JUMPER SUPPLIED BY CUSTOMER 2 DO NOT CONNECT BLUE WIRE INSIDE TRANSMITTER INSULATE STRIPPED END OF BLUE WIRE Section 3 Power up and Calibration A B F G Apply dc power to the transmitter Remove the red protective boot from the sensor end Rinse with deionized water and gently pat dry with a tissue don t wipe or rub Place the pH sensor in the first buffer Install the batteries in the remote controller Note A pH measurement is only as good as the calibration and the calibration is only as good as the buffers used A careful buffer calibration is the first step in making an accurate pH measurement For best results cali brate with buffers having the same temperature as the process Allow time for the sensor and buffers to reach the same temperature If the process temperature is more than 10 C different from the buffer allow at least 20 min utes Be careful using buffers at high temperatures because the of many buffers is undefined above 60 C See the main instruction manual for further information Aim the infrared remote controller IRC at the LCD display Pres
9. UNLESS OTHERWISE SPECIFIED 4 ARTWORK IS SHEET 2 OF 2 TOLERANCES TEM PART NO DESCRIPTION amus fu BILL OF MATERIAL FINISH SILKSCREEN BLACK EPOXY PAINT BAKED iE MIEN NS E eo APPROVALS DATE ROSEMOUNT MACHINED FILLET RADIF 020 AA ste PART NUMBER DN FARSIDE NOMINAL SURFACE FINISH 125 DRAWN N K 04 08 96 MATERIAL CHECKED LABEL 1 5 BASEEFA MATERIAL 151 300 SERIES STAINLESS STEEL A PROJECT 2 3081 PH 015 005 THICK MATERIAL BE ANNEALED amp ENGR APvo ODL Tier 37 ou PASSIVATED MAXIMUM HARDNESS BRINELL 190 FINISH A APLS PRODUCED ON B NO 9241 1 99 00 id NOTES UNLESS OTHERWISE SPECIFIED UMS n NONE 7 02434 SHEET 1 OF2 FIGURE 4 1 Intrinsically Safe BASEEFA Model 3081 Label 31 Od YLNX duO Hdi80E NOIIVWISNi OQILVM3HOS Jepiusue4 dHO Hd 1806 I DOIN 10 OYA 72 7 3Hn5l3 218100 3 154 NDlIVISQNOI 168i 530 32 0 980 SIKL i WADE ANIV QR 30 vig LOR SHOISTATY EL I Am CASH v zv 438915 43123dSNQ JGA p ZP 5 H3MOd 03121234580 V Wi A8 031411832 SI 2 310N 335 133 5 11 3 8HVI ILON 335
10. Quinhydrone hydroquinone ORP standards are also used They are prepared by dissolving excess quinhy drone in either pH 4 00 or pH 6 86 buffer The ORP of the standards at a platinum electrode against a silver silver chloride reference has been measured at 20 25 C and 30 C Temperature ORP in ORP in pH 4 00 buffer pH 6 86 buffer 20 268mV mV 25 mV mV 300 259 There are two disadvantages to using quinhydrone standards First the shelf life is only about eight hours so fresh standard must be prepared daily Second hydroquinone is highly toxic so preparing handling and disposing of the standards requires care Unlike pH calibrations which are generally done using two calibration buffers ORP calibrations are almost always single point calibrations SECTION 14 0 ORP MEASUREMENTS 125 MODEL 3081 pH ORP SECTION 15 0 THEORY REMOTE COMMUNICATIONS SECTION 15 0 THEORY REMOTE COMMUNICATIONS 15 1 Overview of HART Communications 15 2 HART Interface Devices 15 3 AMS Communication 15 1 OVERVIEW OF HART COMMUNICATION HART highway addressable remote transducer is a digital communication system in which two frequencies are superimposed on the 4 to 20 mA output signal from the transmitter A 1200 Hz sine wave represents the digit 1 and a 2400 Hz sine wave represents the digit 0 Because the average value of a sine wave is zero the digital sig nal adds no dc com
11. Sensor Junction Box Preamplifer Wie Function Wing Diagram 399 09 in remote junction box Pt 100 Figure 3 2 Figure 3 5 399 09 62 in remote junction box Pt 100 Figure 3 3 Figure 3 5 399 33 ORP only Pt 100 Figure 3 21 Figure 3 22 Table 3 2 Wiring Diagrams for Model 397 Sensors Sensor Junction Box Preampliier RTD Wire Function Wing Diagram Table 3 3 Wiring Diagrams for Model 396R Sensors Sensors have a BNC connector that the Model 3081 pH ORP transmitter does not accept Cut off the BNC and terminate the coaxial cable as shown in Figure 3 23 Alternatively use a BNC adapter PN 9120531 Set the RTD jumper to the 3K position see Section 2 2 Also program the transmitter to recognize the 3K RTD see Section 8 5 for pH or 10 5 for ORP 15 MODEL 3081 pH ORP SECTION 3 0 WIRING Table 3 4 Wiring Diagrams for Model 396P Sensors Sensor Junction Preamplifier Wire Function Wiring Diagram 396P 01 55 Pt 100 Figure 3 13 3 14 Table 3 5 Wiring Diagrams for Model 396 Sensor Sensor Junction Box Preamplifier RTD WireFunction Wiring Diagram Table 3 6 Wiring Diagrams for Model 389 Sensors Sensors have a BNC connector that the Model 3081 pH ORP transmitter does not accept Cut off the BNC and terminate the coaxial cable as shown in Figure 3 23 Alternatively use a BNC adapter PN 9120531 Set the RTD jumper to the 3K position see Sec
12. SECTION 16 0 GLOSSARY In a combination electrode the measuring electrode and reference electrode are combined in a single body Often the temperature element is included in the body as well A point in a circuit against which voltages are measured Diagnostics also called advanced sensor diagnostics automatically and continu ously monitor the condition of the sensor Diagnostics warn the user of impending or existing problems with the sensor The most useful pH sensor diagnostics are glass impedance and reference impedance Electrode potential is a measure of the tendency of a half reaction to occur as writ ten Electrode potentials are stated relative to a reference electrode which by convention is the normal hydrogen electrode The normal hydrogen electrode is assigned a potential of zero volts An electrochemical cell consists of two half reactions occurring in separate con tainers connected electrically by a salt bridge The electrons produced by the oxi dation half reaction are consumed by the reduction half reaction Because the electrons must pass through an external circuit they can be made to do useful work The drawing below shows a simple electrochemical cell electron flow 3 salt bridge oxidation in this reduction in this beaker produces beaker consumes electrons electrons The voltage of the electrochemical cell measured without drawing current from the cell is the algebraic sum of the potent
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14. 3 Adjust current output to match displayed value a 4 Place transmitter in hold a se 5 Assign pH ORP value to 20 mA output Assign pH ORP value to 4 mA output E 7 View pH value 8 View analog output 9 View transmitter status JI 43 MODEL 3081 pH ORP SECTION 6 0 OPERATION WITH MODEL 275 1 PROCESS VARIABLES VIEW FLD DEV VARS i pH Temp Input Glass Ref 1 2 VIEW PV ANALOG 1 PV is 1 pH rnge 1 3 i 1 1 1 i View status i 2 DIAG SERVICE TEST DEVICE View status Master reset View history Loop test CAL IBRAT TON BUFFER CALIBRATION Begin procedure slope offset pH STANDARDIZE Begin procedure pH 0 offset ADJUST TEMPERATURE Begin procedure rem Temp comp Man terp Trim analog output Hold mode i i i 1 1 1 3 BASXC SETUP Tag PV RANGE VALUES 1 PV LRV PV URV pH PV rnge xfer fun DEVICE INFORMATION Tag Descriptor Message Snsr text Date Figure 6 2 is continued on page 41 FIGURE 6 2a pH Menu Tree HART MODEL 3081 pH ORP 4 DETAILED SETUP SENSORS 1 2 SIGNAL CONDITION 1 2 3 4 5 OUTPUT CONDITION 1 I i 1 2 DE
15. Gonverting Voltage to eaa a 116 13 6 Glass Electrode Slope oe e eset io 117 13 7 Buffers and Calibration nenne 117 13 9 Sopotential plas soot ita eret cete ivo ke denota te He Eo acte da gu 118 13 9 A Junction Potential Mismatch 000 0 101 118 13 10 Sensor co ort ere lere Pe ore 119 13 11 Shields Insulation and 119 14 0 ORP MEASUREMENTS siajii inasnan dadadada iadaa edadia 120 14 1 General 120 14 2 Measuring 121 14 3 Reference Electrode setis akaun us aqa tasa 121 14 4 Liquid Junction Potential UL LLL nnnm nennen 121 14 5 Relating Cell Voltage to ORP 122 14 6 Concentration 122 14 7 Interpreting ORP Measurement 123 14 8 GallbratioD ice 124 15 0 THEORY REMOTE COMMUNICATIONS 126 15 1 Overview of HART 0 126 15 2 HART Interface
16. PROGRAM Snr EXIT 1100 NEXT ENTER IMPORTANT 70 6 SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 8 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the ISOPOtntAL sub menu appears Press ENTER The screen displays the tCOEFF prompt Use the editing keys to change the display to the desired solution temperature coefficient The allowed values are 0 044 to 0 028 pH C To enter a negative coefficient press until no digit is flash ing Then press or v to display the negative sign Press ENTER to save The screen displays the ISO prompt The number showing in the display is the oper ating isopotential pH The transmitter calculates the operating isopotential pH from the transmitter isopotential pH and the solution temperature coefficient If the solution temperature coefficient is 0 00 the operating isopotential pH is 7 00 If the solution temperature coefficient is different from 0 00 the operating isopotential pH will be dif ferent from 7 00 It is ALWAYS better to enter the solution temperature coefficient as described in step 3 and let the transmitter calculate the operating isopotential pH To move to the next prompt without changing the value press NEXT The screen displays the Snr prompt The flashing display is the current transmitter isopotential point Use the editing keys to change the transmitter isopotential pH to match the sensor isopotential pH The limi
17. These potentials are listed below 1 the potential of the reference electrode inside the glass electrode 2 the potential at the inside surface of the glass mem brane 3 the potential of the external reference electrode FIGURE 13 5 The Origin of Liquid Junction Potentials The figure shows a thin section through a pore in the junction plug The junction separates a solution of potassium chloride on the left from a solution of hydrochloric acid on the right The solutions have equal molar concentration Driven by concentration differences hydrogen ions and potassium ions diffuse in the directions shown The length of each arrow indicates relative rates Because hydrogen ions move faster than potassium ions positive charge builds up on the left side of the section and negative charge builds up on the right side The ever increasing positive charge repels hydrogen and potassium ions The ever increas ing negative charge attracts the ions Therefore the migration rate of hydrogen decreases and the migration rate of potassi um increases Eventually the rates become equal Because the chloride concentrations are the same chloride does not influ ence the charge separation or the liquid junction potential 116 MODEL 3081 pH ORP 4 the liquid junction potential The second term 0 1984 T pH is the potential in mV at the outside surface of the pH glass This potential depends on temperature and on the pH of the sample Assumin
18. 2 Calibrate the sensor transmitter loop if a 1 C accuracy is NOT acceptable or b the temperature measurement is suspected of being in error NOTE A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing set tings use a different security code for each nearby transmit ter See Section 5 7 Security 9 4 2 Procedure 1 Place the transmitter in ORP mode See Section 10 6 3 steps 1 3 After selecting and saving OrP press EXIT twice to return to the main display Place the ORP sensor and a calibrated reference thermometer in an insu lated container of water at ambient temperature Be sure the temperature element in the sensor is completely submerged by keeping the sensor tip at least three inches below the water level Stir continuously Allow at least 20 minutes for the standard thermometer sensor and water to reach constant temperature Enter the CALIBRATE menu by pressing CAL on the IRC The Std sub menu appears pictured above left At the Std sub menu press NEXT The tEMP AdJ sub menu appears Press ENTER to display the temperature editing prompt Compare the temperature displayed by the transmitter with the tempera ture measured with the reference thermometer If the readings are differ ent use the editing keys to change the flashing display to the value deter mined with the reference thermometer The reading cannot be changed by more than
19. 4 IN TO EXPOSE THE WIRES 3 LOCATE THE 2 COAXIAL CABLES AND PREPARE AS FOLLOWS SEE BELOW INSULATE EXPOSED BRAID BLACK CABLES SEE PREP BELOW PREPARE THE COAX CABLE AS FOLLOW STRIP INSULATING BLACK SHEATH BACK ABOUT 1 IN 38 1 BRAID 3B SEPARATE THE BRAID FROM THE INNER BLACK CONDUCTIVE SHEATH BLACK CONDUCTIVE SHEATH BRAID BLACK INSULATION 3C SOLDER INSULATED WIRE USER SUPPLIED TO BRAID IF NEEDED INNER BLACK CONDUCTIVE SHEATH INSULATED WIRE BLACK INSULATING 3D STRIP BLACK CONDUCTIVE SHEATH 1 IN TO EXPOSE ORANGE OR GRAY DEPENDING ON WHICH COAX YOU ARE PREPARING BLACK 25 4 CONDUCT I VE 1 0 INNER BLACK CONDUCTIVE WARNING IF ORANGE OR GRAY SHEATH IS IN CONTACT WITH THE EXPOSED LEADS OR IS NOT PREPARED PROPERLY INSULATED WIRE IT MAY CAUSE AN ELECTRICAL SHORT BLACK INSULATION SHEATH INSULATE EXPOSED BLACK SHEATH BRAID AREA ORANGE OR GRAY INSULATION INSULATED WIRE FIGURE 3 24 Preparation of Raw Connecting Cable PN 9200273 SECTION 3 0 WIRING MODEL 3081 pH ORP uo 1 HOSN3S 949 995 1 8 ees 5 5 ees 5 eos 10 peno s 3965 985 All yoo dy 105 25 y SSOP JEU 01 8 ees 2 6 9148 ees 40 peyo veze 16 40 peuols Jejdnoo YOO wi O WeY ul dn 10sues y 108095 2115614 A s op dn onsejd
20. High impedance warning 40 kilohms 26 lt Low impedance warning 20 megohms gt e Low impedance fault 10 megohms o 5 5 E 80 8 2 E 9 FIGURE 10 1 Suggested Warning and Failure Limits for Low Impedance Reference Electrodes The impedance of a typical silver silver chloride reference electrode is less than 40 kilohms If the impedance is greater than about 140 kilohms the reference electrode has failed Failure is usually caused by a plugged or coated reference junction or a depleted electrolyte fill solution gel The refer ence impedance will also be high if the sensor is out of the process liquid FIGURE 10 2 Suggested Glass Impedance Warning and Failure Limits for a Glass Reference Electrode Typical glass impedance is about 100 megohms at 25 C A bro ken or cracked electrode has an impedance of 10 megohms or less A glass impedance greater than 1000 megohms suggests the electrode is nearing the end of its service life High imped ance may also mean the electrode is not immersed in the process liquid SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS MODEL 3081 pH ORP 10 4 3 Procedure PROGRAM 05 1 Press PROG on the infrared remote controller IRC EXIT NEXT ENTER 7 2 Press NEXT until the diAGnOStIC sub menu appears Press ENTER The screen displays the rOFFSt prompt Use the ed
21. 0 mA During hold the transmitter displays the present pH and temperature The word HOLD appears in the display FAULT A fault is a system disabling condition When the transmitter detects a fault the fol lowing happens a The display flashes b The words FAULT and HOLD appear in the main display c A fault or diagnostic message appears the temperature current display area d The output signal remains at the present value or goes to the programmed fault value Permitted values are between 3 80 and 22 00 mA If the transmitter is in HOLD when the fault occurs the output remains at the programmed hold value To alert the user that a fault exists the word FAULT appears in the main dis play and the display flashes A fault or diagnostic message also appears f If the transmitter is simulating an output current when the fault occurs the transmitter con tinues to generate the simulated current To alert the user that a fault exists the word FAULT appears in the display and the display flashes 0 lfasensor fault occurs a 1 mA signal appears at TB 14 see Section 2 5 2 Sensor faults are rEF FAIL rEF WArn GLASSFAIL and GLASSWARrn See Section 12 0 for more information about sensor faults DAMPEN Output dampening smooths out noisy readings But it also increases the response time of the output To estimate the time in minutes required for the output to reach 9596 of the final reading following a step change divide
22. 1 1 Setup for the Models 381 52 385 04 396P 02 54 396P 02 55 and 396R 54 without a junction box A The factory setting of the preamplifier switch is in the appropriate location so no adjustment is necessary B Mount the transmitter in the desired location Most installations use PN 2002577 pipe mounting bracket C Continue the start up with Section 2 Wiring Section 1 2 Setup for Sensor Models 381 55 385 03 and 396P 01 55 without a junction box A This section shows how to set the preamplifier switch and should be done prior to installation of the transmitter B Loosen the cover lock nut on the Model 3081pH ORP transmitter until the tab disengages from the circuit end cap Unscrew and remove the cap Unscrew the three bolts holding the circuit board stack in the enclosure C Pull up on the display board Do not disconnect the ribbon cable between it and the CPU board The CPU and analog boards are joined by a pin and socket connector along the bottom edge of the boards Carefully pull the boards apart and remove the CPU board The analog board is on the bottom and remains in the enclosure See Figure 1 below D The analog board is shaped like a circle with an arc missing Directly opposite the straight side is a slide switch Change the switch position to the sensor or j box setting by sliding the switch closer to the edge of the board See Figure 2 below E To reassemble the stack place the display board on the CPU board Be sure the
23. 15 C Press ENTER The value will be saved and the display will return to the tEMP AdJ sub menu To leave the CALIBRATE menu press EXIT Check linearity by measuring the temperature of water 10 to 15 C cooler and 10 to 15 C warmer than the water used for calibration Because of the time required for the temperature element in the sensor to reach con stant temperature a well insulated container or better a constant tem perature bath is required for this step 73 MODEL 3081 pH ORP SECTION 9 0 CALIBRATION OF ORP MEASUREMENTS 9 5 Standardization 9 5 1 Purpose This section describes how to prepare ORP standard solutions and how to make the transmitter reading match the ORP of the standard Procedures for making ORP standards are taken from ASTM Method D1498 93 9 5 2 Preparation of ORP Standard Solutions ASTM D 1498 93 gives procedures for making iron Il iron and quinhydrone ORP standards The iron II iron III standard is recommended It is fairly easy to make and has a shelf life of about one year In contrast quinhydrone stan dards contain toxic quinhydrone and have only an 8 hour shelf life Iron 11 iron III standard is available from Rosemount Analytical as PN R508 16OZ The ORP of the standard solution measured against a silver silver chloride reference electrode is 476 20 mV at 25 C NOTE A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally c
24. 2 Turn off sensor diagnostics See Section 8 4 Turn off automatic temperature compensation Set manual temperature compensation to 25 C See Section 8 5 Disconnect the sensor and wire the sensor side of the junction box as shown in Figure 12 8 Leave the inter connecting cable between the junction box and transmitter in place Attach a jumper between TB1 7 REF and 1 10 pH INCLUDES PREAMPLIFIER BOARD PN 23557 00 From this point on continue with steps 6 through 9 in Section 12 8 2 For testing using a standard millivolt Source be sure to remove the jumper between 1 7 and TB1 10 before connecting the standard mil livolt source 1 4 3 or 4 oim 74 20 m 34 20 mi RNC 182 NO CONNECTION E FARSIDE 24vDC io EXTENSION CABLE PGINT TO POINT WIRING TERMINALS 2 TO 12 FIGURE 12 8 pH Simulation When the Preamplifier Is Located in a Remote Junction Box or in a Sensor Mounted Junction Box MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 8 4 pH Simulation with the Model 381 Sensor s Dy gv d o mw oc Verify that switch S 1 is set to sensor or junction box See Section 2 2 Turn off sensor diagnostics See Section 8 4 Turn off automatic temperature compensation Set manual te
25. 3 22 Wiring Diagram for Model 399 33 25 MODEL 3081 pH ORP TABLE OF CONTENTS TABLE OF CONTENTS CONT D LIST OF FIGURES CONT D Number Title Page 3 23 Procedure for Removing BNC Connector and Preparing Coaxial Cable for Connection to the Model 3081 pH ORP 26 3 24 Preparation of Raw Connecting Cable PN 9200273 27 4 1 Intrinsically Safe BASEEFA Model 3081 pH ORP Label 31 4 2 Installation for Model 3081 pH ORP 32 4 3 CSA Installation for Model 3081 pH ORP 34 4 4 Explosion Proof Installation for Model 3081 pH ORP 36 5 1 Process Display ziii reed eire kv EE d 37 5 2 Program Display uiuit aee eee Sio u usss 37 5 3 Infrared Remote Controller ii i a ua au arse 38 5 4 Menu Tre fOr pH s y 39 5 5 oM 40 6 1 Connecting the HART Communicator essen 42 6 2 Monu tor HART eiecit ace i 44 6 3 Menu Tree for 2 06 44 0 1 0 0000 pain 46 8 1 Suggested Glass Impedance Warning and Failure Lim
26. 30 42 and 381pHE 31 42 as 18 3 4 Wiring Diagram for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 after removing BNC and terminating cable Wiring Diagram for Models 399 09 10 62 381pH 30 42 and 381pHE 31 42 as received Wiring directly to the transmitter 18 3 5 Wiring Diagram for Models 399 02 399 09 381pH 30 41 after removing BNC and terminating cable Wiring Diagram for Model 399 09 10 62 381pH 30 42 and 381pHE 31 42 as received Wiring through a remote junction box to the transmitter 18 3 6 Wire Functions for Models 397 50 397 54 396 50 396 54 396R 50 60 396R 54 60 389 02 50 389 02 54 before removing BNC and terminating 19 3 7 Wire Functions for Models 397 50 397 54 396 50 396 54 396R 50 60 396R 54 60 389 02 50 389 02 54 after removing BNC and terminating cable Wire Functions for Models 397 54 62 396 54 62 and 389 02 54 62 as received 19 3 8 Wiring Diagram for Models 397 50 397 54 396 50 396 54 389 02 50 and 389 02 54 after removing BNC and terminating cable Wiring Diagram for Models 397 54 62 396 54 62 and 389 02 54 62 as received Wiring Directly tothe Transmiter usus s auqa qapa a seed 19 3 9 Wiring Diagram for Models 397 50 397 54 396 50 396 54 396R 50 60 396R 54 60 389 02 50 389 02 54 after removing BNC and terminating c
27. 4 3 Pipe Mounting See Figure 2 5 The pipe mounting kit PN 2002577 accommodates 1 1 2 to 2 in pipe _161 3_ 2 PLACES V CIRCUIT TERMINAL END END MILLIMETER INCH THREADED CAP 587 7 TERMINAL BLOCK TERMINAL END CAP OMITTED 3 FOR CLARITY 2 8 4544 NPT THIS VIEW 2 PLACES KIT 2IN PIPE WALI MOUNTING BRACKET ORDER PN 2002577 AS A SEPARATE ITEM SUPPLIED BY CUSTOMER 9 525 a DIA 375 DI 4 MQUNTING HOLES 35 687 1 405 71 574 4 728 3 4 14 FNPT 2 PLACES 5 16 18 NUT BRACKET HOLES PATTERN FOR WALL MOUNTING 5 16 WASHER DWG NO REV 40308104 G 1 4 20 SCRE SCREWS FURNISHED WITH MOUNTING KIT ONLY m NOT FURNISHED WITH TRANSMITTER f U BOLT E 2 xu 7 4 1 2 IN TO 2 IN PIPE CUSTOMER FURNISHED DWG NO 40308103 FIGURE 2 5 Using the Pipe Mounting Kit to Attach the Model 3081 pH ORP Transmitter to a Pipe MODEL 3081 pH ORP SECTION 2 0 INSTALLATION 2 5 POWER SUPPLY CURRENT LOOP 2 5 4 Power Supply and Load Requirements 1380 ohms Refer to Figure 2 6 maximum The minimum power supply voltage is 12 5 Vdc and the maximum is 42 4 The top line on the graph gives the voltage required to maintain at least 12 5 Vdc atthe transmitter terminals when the output sig nal is 22 mA The lower line is the supply voltage required to maintain a
28. 43 55 21 MODEL 3081 pH ORP 22 CLEAR INNER DRAIN WHITE RTD TC SHIELD WHITE RED RTD SENSE RED RTD TC IN 3 CLEAR REFERENCE SHIELD Gu GRAY REFERENCE IN BLUE SOLUTION GROUND BNC pH mV IN FIGURE 3 15 Wire functions for Model 385 02 MODEL 3081pH ORP TRANSMITTER SOL pH ps GUARD CLEAR WHITE WHITE RED RED EXTENSION CABLE PN 9200273 UNPREPPED OR OR PN 23646 01 PREPPED 182 FARSIDE WHITE BLACK SENSOR MOUNTED JUNCTION BOX INCLUDES PREAMPLIFIER BOARD PN 23557 00 213145161880 TB1 SENSOR CABLE NOTES 1 PLACE PREAMPLIFIER SELECTION SWITCH S1 IN SENSOR JUNCTION BOX POSITION SEE SECTION 2 2 2 SEE FIGURE 3 24 FOR TERMINATION OF RAW INTERCONNECTING CABLE PN 9200273 3 4 DO NOT CONNECT BLUE WIRE INSULATE STRIPPED END OF WIRE TO AVOID ACCIDENTAL JUMPER SUPPLIED BY CUSTOMER CONNECTIONS FIGURE 3 16 Wiring diagram for Model 385 02 SECTION 3 0 WIRING MODEL 3081 pH ORP SECTION 3 0 WIRING ORANGE COAX SHIELD REFERENCE IN RED pH IN NOTE MODEL 328A 08 HAS UNDRESSED COAXIAL CABLE SEE SENSOR INSTRUCTION SHEET FOR CABLE PREPARATION PROCEDURE FIGURE 3 17 Wire functions for Model 328A 07 MODEL 3081pH ORP TRANSMITTER SOL pH a tJ SENSOR CABLE NOTES PLACE PREAMPLIFIER SELECTION SWITCH 51 IN TRANS MITTER POSITION SEE SECTION 2 2 JUMPERS SUPPLIED BY CUST
29. Date DfAGNOSTICS 1 Diagnostics Diagnostics Ref unit Ref unit RFL RWH 0 timit LOCAL DISPLAY ID AG LOI units i i l i 1 1 i i 1 1 l i l i i i i 1 i i i i 1i SENSORS OUTPUTS DIAGNOSTICS DEVICE INFORMATION LOCAL DISPLAY When Ref unitisHohms 2 When Ref unit ekohms FIGURE 6 3b ORP Menu Tree HART MODEL 3081 pH ORP SECTION 7 0 CALIBRATION OF pH MEASUREMENTS SECTION 7 0 CALIBRATION OF pH MEASUREMENTS 7 1 General 7 2 Entering and Leaving the Calibrate Menu 7 3 Using the Hold Function 7 4 Temperature Calibration 7 5 X Auto Calibration 7 6 Manual Calibration 7 7 Making the Transmitter Reading Match Second pH Meter Standardization 7 1 GENERAL The Calibrate menu allows the user to calibrate the pH and temperature response of the sensor The transmitter does a two point pH calibration Both manual and auto calibration are available In auto calibration the transmitter automatically stores temperature corrected calibration data once readings have met programmed stability lim its In manual calibration the user enters buffer values and judges when readings are stable The transmitter reading can also be made to match the reading of a second pH meter Temperature calibration is a one point stan
30. Div 2 Groups A B C amp D T5 Tamb 40 Weight Shipping Weight 10 16 10 Ib 4 5 kg 4 5 kg Weights and shipping weights are rounded to the nearest whole pound amp G 1380 ohms maximum Operating Region 24 Power supply voltage Vdc Without HART Communication 42 4 Vdc 30 36 42 maximum MODEL 3081 pH ORP 1 4 SPECIFICATIONS pH pH Input Range 0 to 14 pH Temperature Input Range 5 F to 248 F 15 C to 120 C Output Scale Expansion Continuously expandable between pH 0 and 14 Accuracy at 25 C 0 01 pH Repeatability at 25 C 0 01 pH Resolution 0 01 pH 0 1 C or F Stability at 25 C 0 25 per year Temperature Compensation Automatic or manual between 5 F to 248 F 15 C to 120 C Solution Temperature Compensation Transmitter will convert pH measured at any temperature to the pH at 25 C Temperature coefficient is programmable between 0 044 pH C and 0 028 pH C Calibration Automatic two point and manual two point buffer calibration For automatic calibration the trans mitter recognizes NIST DIN 19266 and 19267 JIS 8802 BSM Merck and Ingold buffers 1 6 ORDERING INFORMATION SECTION 1 0 DESCRIPTION AND SPECIFICATIONS 1 5 SPECIFICATIONS ORP ORP Input Range 1400 to 1400 mV Temperature Input Range 5 F to 248 F 15 to 120 C Output Scale Expansion Continuously expandable between 1400 and 1400 mV Accuracy at 25 C 1 mV Repeatabi
31. FactOn appears in the display 9 Press FactOFF appears Press ENTER to store the settings 10 Press EXIT repeatedly until the main display reappears If the message does not clear or problems persist the electronics have failed Replace the electronic board stack PN 23574 02 12 5 TROUBLESHOOTING WHEN NO DIAGNOSTIC MESSAGE IS SHOWING If no diagnostic message is showing locate the symptom s in the table below and refer to the appropriate section for assistance SYMPTOM SECTION Id 000 appears in display when trying to program or calibrate transmitter Error message flashing in display Transmitter does not respond to remote controller Calibration Problems SLOPE Err or SLOPE Err LO appears after calibration attempt bF1 or bF2 continuously flashes during auto calibration pH reading in buffer drifts during manual calibration Measurement Problems Sensor does not respond to known pH changes Buffer calibration is acceptable process pH is slightly different from expected value Buffer calibration is acceptable process pH is grossly wrong and or readings are noisy Temperature reading is inaccurate HART communicator does not work Transmitter problems No display Display segments missing or display incorrect Transmitter locked up all display segments lit Transmitter periodically restarts itself 102 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 5 1 Id 000 in Display A security code has been programmed into the trans
32. Figure 15 2 for a sample screen AMS communicates through a HART compatible modem with any HART transmitters including those from other manufacturers AMS is also compatible with FOUNDATION Fieldbus which allows future upgrades to Fieldbus instruments For more information about AMS including upgrades renewals and training call Fisher Rosemount Systems Inc at 612 895 2000 iS AMS Application Device Connection View HA Eile Edit View Window Help sel le m EI pr Properties eur Cascade Arrange Icons Close All 1 Device Connection View AMS Device Connection View Device tatus Bar Print Print Preview AMS Explorer User Configurations View Exit Device Templates View Suppart Information Alert Monitor License Agreement License Certificate Using Help Reresn About AMS FIGURE 15 2 AMS Main Menu Tools 127 MODEL 3081 pH ORP TERM Acid Activity Alkalai metal AMS Balco RTD Base Buffer calibration Buffer Calibration 128 SECTION 16 0 GLOSSARY SECTION 16 0 GLOSSARY DEFINITION When dissolved in water acids increase the hydrogen ion concentration Pure water at 25 C contains 1 x 10 7 moles per liter of hydrogen ions and equal concentration of hydroxide ions An acid increases the hydrogen ion centration above the value found in pure water and decreases the hydroxide ion concentration Howev
33. Keep the sensor wires attached and jumper TB 3 and TB 4 If the diagnostic message disappears either the RTD return or RTD sense wire is broken To verify a broken wire disconnect the leads and measure the resistance between them Installing the jumper completes the circuit but bypasses the three wire function The transmitter no longer corrects for changes in lead wire resistance with temperature Replace the sensor as soon as possible If the diagnostic message remains go to step C The cable connecting the sensor to the transmitter may be too long Test using a sensor with a shorter cable If shortening the cable eliminates the problem move the transmitter closer to the sensor It may also be possible to increase diameter of the RTD wires Consult the factory for assistance If the diagnostic message remains go to step D Check the performance of the transmitter Simulate both temperature and pH See Section 12 4 6 steps B and C for temperature simulation and Section 12 8 for pH simulation If the transmitter fails either simulation the electronic board stack PN 23574 02 should be replaced If the transmitter passes the simulations the transmitter is in good condition and the sensor should be replaced 12 4 8 InPUt WArn InPUt WArn means that the input value or the calculated pH is outside the measurement range The measured pH is less than 2 or greater than 16 Troubleshooting Flowchart InPUt WArn A Check for miswir
34. Lead resistance is about 0 05 ohm ft at 25 C Therefore 15 feet of cable increases the resistance by about 1 5 ohm The resistance between the RTD return and RTD sense leads should be less than 2 ohms TABLE 12 1 RTD Resistance Values Resistance Resistance Resistance 100 0 ohms 1000 ohms 2670 ohms 103 9 ohms 1039 ohms 2802 ohms 107 8 ohms 1078 ohms 2934 ohms 109 6 ohms 1096 ohms 3000 ohms 111 7 ohms 1117 ohms 3067 ohms 115 5 ohms 1155 ohms 3198 ohms 119 4 ohms 1194 ohms 3330 ohms 123 2 ohms 1232 ohms 3472 ohms 127 1 ohms 1271 ohms 3594 ohms 130 9 ohms 1309 ohms 3726 ohms 134 7 ohms 1347 ohms 3858 ohms 138 5 ohms 1385 ohms 3990 ohms If a connection is open or shorted and it should not be the sensor has failed Replace the sensor If the RTD is different from what was expected for example the sensor contains a Pt 100 not a Pt 1000 RTD reset the jumper and reconfigure the software to match the actual RTD If the measured resistances are acceptable go to step C MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING C Check the transmitter 1 Disconnect the RTD sensor leads and wire the circuit shown in Figure 12 4 Set the resistance to the value for 25 C shown in Table 12 1 The measured temperature should equal 25 C to within 1 C RTD sense Standard resistor s to simulate RTD FIGURE 12 4 Temperature simulation into the Model 3081 pH ORP transmitter If the measured temp
35. PREPARATION OF EXTENSION SEE SENSOR MANUAL FOR PREPARATION OF EXTENSION CABLE PN 661 646983 DISCONNECT WHITE GUARD WIRE FROM TB 7 AND INSU LATE STRIPPED END FIGURE 3 19 Wiring diagram for Model 320HP 10 55 FIGURE 3 20 Wiring diagram for Model 320HP 10 58 24 MODEL 3081 pH ORP SECTION 3 0 WIRING WHITE RTD TC RETURN BLACK RTD TC IN RED REFERENCE IN CLEAR COAX SHIELD WHITE ORP mV IN FIGURE 3 21 Wire Functions for Model 399 33 MODEL 3081pH ORP TRANSMITTER pH GNO GUARD SENSOR CABLE WHITE COAX FIGURE 3 22 Wiring Diagram for Model 399 33 25 SECTION 3 0 MODEL 3081 pH ORP WIRING PREPARE THE COAX CABLE AS FOLLOWS CUT OFF BNC CONNECTOR BNC CUT INSULATION 2 5 INCH BRAID SEPARATE BRAID FROM BLACK CONDUCTIVE SHEATH AND CUT BRAID 0 5 INCH FROM INSULATION conbucrive BRAID COAX BNC CUT BACK CONDUCTIVE BLACK BRAID i AND SOLDER BUSS WIRE TO BRAI ORANGE INSULATION SOLDER BUSS WIRE CUT ORANGE INTERNAL INSULATION O 5 INCH LEAVING A SEPARATION BETWEEN THE BLACK SHEATH ORANGE AND THE CENTRAL CONDUCTOR pH ey BUSS REF 6 INSULATE EXPOSED BLACK SHEATH BRAID AREA ORANGE pH BUSS REF INSULATION FIGURE 3 23 Procedure for Removing BNC Connector and Preparing Coaxial Cable 26 MODEL 3081 pH ORP SECTION 3 0 WIRING 1 STRIP BACK OUTER BRAID AND FOIL ABOUT 4 IN FROM END OF CABLE 2 STRIP INDIVIDUAL SHEATHS BACK ABOUT
36. Press ENTER to save the value To leave the slope unchanged press EXIT To leave the CALIBRATE menu press EXIT 55 MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 1 General 8 2 X Entering and Leaving the Program Menu 8 3 Output Ranging 8 4 Diagnostic Parameters 8 5 Temperature Related Settings 8 6 Display Units 87 Buffer Calibration Parameters 8 8 Isopotential Parameters 8 9 Generating a Test Current 8 1 GENERAL This section describes how to do the following assign pH values to the 4 and 20 mA outputs set the current generated by the transmitter during hold set the current generated by the transmitter when a fault is detected change sensor diagnostic limits enable and disable automatic temperature compensation change the units of the displayed variables program a security code identify buffers for auto calibration 9 change the transmitter isopotential point 10 simulate output currents for testing N O 0 Factory default settings are given in Table 8 1 If default settings are acceptable the transmitter is ready for calibration See Section 7 0 Calibration of pH Measurements Once a setting has been changed there is no way to automatically reset the transmitter to factory defaults Settings must be returned to default values one at a time Figure 5 4 shows the menu tree 8 2 ENTERING AND LEAVING THE PROGRAM MENU Pres
37. Section 8 5 Disconnect the sensor and wire the transmitter as shown in Figure 12 7 Attach a jumper between TB 7 REF IN and TB 10 pH IN Measure the voltage Press DIAG on the IRC The InPut voltage in millivolts will appear in the temperature output area The main display will continue to show pH The measured voltage should be 0 mV and the pH should be approximately 7 Because the calibration data in the transmitter may be offsetting the input voltage the displayed pH may my not be exactly 7 0 If the actual readings are close to expected the transmitter is probably operating properly FIGURE 12 7 pH Simulation When the If a standard millivolt source is available remove the jumper between Preamplifier Is Located in the Transmitter TB 7 and TB 10 and connect the voltage source Following the procedure in Section 7 5 calibrate the transmitter Use 0 0 mV for pH 7 bF1 and 177 4 mV for pH 10 bF2 If the transmitter is working it should accept the calibration Voltage mV To check linearity leave autocalibration and return to the main display Set the voltage source to the values in the table and verify that the pH reading matches the expected value 12 8 3 pH Simulation When the Preamplifier Is Located in a Remote Junction Box or in a Sensor Mounted 1 2 3 4 Junction Box Verify that switch S 1 is set to sensor or junction box See Section 2
38. Sections 13 5 and 13 6 the factor relating the cell voltage to pH is also a function of temperature The construction of each electrode and the electrical poten tials associated with it are discussed in Sections 13 2 13 3 and 13 4 13 2 MEASURING ELECTRODE Figure 13 2 shows the internals of the measuring electrode The heart of the electrode is a thin piece of pH sensitive glass blown onto the end of a length of glass tubing The pH sensitive glass usually called a glass membrane gives the electrode its common name glass electrode Sealed inside the electrode is a solution of potassium chloride buffered at pH 7 A piece of silver wire plated with silver chloride contacts the solution The silver wire silver chloride combination in contact with the filling solution constitutes an internal reference elec trode Its potential depends solely on the chloride concen tration in the filling solution Because the chloride concen tration is fixed the electrode potential is constant As Figure 13 2 shows the outside surface of the glass membrane contacts the liquid being measured and the inside surface contacts the filling solution Through a com plex mechanism an electrical potential directly proportion al to pH develops at each glass liquid interface Because the pH of the filling solution is fixed the potential at the inside surface is constant The potential at the outside sur face however depends on the pH of the test solutio
39. VIEW FLD DEV VARS 1 ORP t 2 Temp 3 ReF VIEW PV ANALOG 1 3 PV is f 2 ORP 3 4 PV i i view status 2 DIAG SERVICE TEST DEVICE View status Master reset View history Loop test CALIBRATION BUFFER CALIBRATION N A for ORP i i STANDARDIZE pv 1 Begin procedure 2 GRP 3 Q offset l i 1 i ADJUST TEMPERATURE procedure 2 Temp analog output Hold mode 3 BASIC SETUP Tag PV RANGE VALUES 1 PV LRV PV ORP PV rage xfer Tun DEVICE INFORMATION 1 Tag D scriptor Message Snsr text Date Figure 6 3 is continued on page 43 FIGURE 6 3a ORP Menu Tree HART MODEL 3081 pH ORP SECTION 6 0 OPERATION WITH MODEL 275 4 DETAILED SETUP i SENSORS MAIN SENSOR is Convention imped comp TEMPERATURE Temp angr SIGNAL CONDITION 1 PV 2 PV URV GRP PV X rage xfer fund OUTPUT COMDITION 1 AMALOG OUTPUT ANALOG OUTPUT 1 PV AQ 2 PV AO Damp 3 PV Hold PY Fault Loop test frim analog output i I i gt i i i i 3 i f i l i Poll addr Temp unit Ref unit i Pv 18 i Burst option Burst mode i Num resp presans 4 i I I i i 5 i i i 1 1 5 DEVICE INFORMATION 1 Tag Descriptor Wessage Snsr text
40. VL O AZ JHON 38015 HON 31943435 JON SnivHvVddV 31dWIS 30 SIN3W3HIDO3H IHL LIIW 11 6 550538 5 01110 02 ONIMOT1103 384 1334 TIWHS H314JIldWvV3ud 1VH531NI HLIM dHO H 1808 TICON 713 000461 SI 318VO ONY dAV3Sd YILLINSNYYL N33 amp 138 SHLONST 318v W WIXVW 79 oo T ox o sz BOVSUSINI USLLIWSNVYL 310W3N SUZ13 YuVd AIIlN3 51 o 506 os of reor 55 12 SPA 13000 91 won g 91 61 8l SIYNINS3L WNOIS 5 ori se ALIINS 1805 ZL 1 181 SY3LINVYYd 1806 13004 indina 919223 622 130000 114 1806 13000 116 21 919529 522 13008 2 180 TIGON 2 lt 20 gt 251 214251 03 gt 3H3HM 9 4093 12 lt 093 3H3HM SNOILIGNGO ONIMDT104 AHL 9NILIIN SYBLINVEVd ALIIN3 30 135 JINIS 25 01110 02 V HLIM H3H13901 ASN 804 Q3AO0HddV N338 3AVH 513 2 08 SNIMOTI03 3Hl 1330 TIVHS 1 0 3Hi OL 03123 02 5321 3078 S H31HHVB 031311832 VSI OL 180 13004 3Hi 123NNOO J3ldi ddWviSd 310W3H O0 9vS c 1710 Swa S110A 052 9 VIIN310d cce Eae pen NI H3LLIWSN 1805 TICON JHL 30 ISNA 0 03217110 38 AWW 00 19552 YO 00 9rS Z H313lndAv3Hd V 5 03141934 SNOILIONOO ONIADTID3 133W TTvHS 3002 19915152373 NVIQVNVO JHL
41. a voltage dif ference The voltage difference AV is calculated from the equation AV 0 1984 t 273 14 ApH where t is the temperature in C The voltage difference called the reference offset is then added to subsequent pH cell voltage measurements before the voltage is converted to pH See Sections 13 5 through 13 7 for details on how the pH meter converts voltage into pH readings Before the transmitter accepts the offset it compares the offset with the value rOFFSt programmed into the transmitter in Section 8 4 Diagnostic Parameters If the difference exceeds rOFFSt the transmitter will not accept the data and will not update the display to the corrected pH MODEL 3081 pH ORP CALIBRATE CALIbrAtE EXIT NEXT ENTER Std EXIT NEXT ENTER 2 CALIBRATE Std BEDO EXIT NEXT ENTER 5 6 7 CALIBRATE ER 00 NEXT ENTER SECTION 7 0 CALIBRATION OF pH MEASUREMENTS NOTE Atransmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each near by transmitter See Section 5 7 Security 7 7 3 Procedure CALIBRATE 1 Enter the CALIBRATE menu by pressing CAL on the IRC The CALibrAtE sub menu appears pictured above left At the CALibrAtE sub menu press NEXT The Std sub menu appears With the Std sub menu displayed press ENTER The Std prompt appears Be sure that the process pH
42. atom The electron consumed by the silver ion comes from a second half reaction occurring elsewhere in the system HART is an acronym for highway addressable remote transducer HART is a dig ital communication system in which digital signals are superimposed on the 4 20 mA output signal from the transmitter Using a HART communicator connected across the output the user can view process measurements and can calibrate and program the transmitter MODEL 3081 pH ORP Hold function Intrinsically safe Isopotential pH Isotherm Junction box Liquid junction potential Measuring electrode Menu Molar concentration Nernst equation Non incendive ORP Oxidation SECTION 16 0 GLOSSARY During hold the Model 3081 pH ORP transmitter generates a pre programmed output current or remains at the last value Placing the transmitter in hold avoids false alarms and unwanted operation of chemical dosing pumps while the sensor is being calibrated or cleaned An enclosure is intrinsically safe if a spark or heat generated during normal oper ation or during a fault likely to occur in practice is incapable of igniting the gas vapor or dust surrounding the enclosure The isopotential pH is the pH at which voltage is independent of temperature The transmitter isopotential pH is 7 00 The isopotential pH of the measuring cell may be different from 7 00 The greater the difference between the transmitter and cell isopotential pH the g
43. attached to sensor mounting plate MODEL 3081 pH ORP SECTION 1 0 DESCRIPTION AND SPECIFICATIONS ACCESSORIES 515 DC loop power supply see Section 1 2 1 for details 3 Ib 1 0 kg 230A Two alarm module see Section 1 2 2 for details 3 Ib 1 5 kg 275 HART communicator order from Rosemount Measurement 800 999 9307 NA 23572 00 Infrared remote controller includes two 1 5 V AAA alkaline batteries 1 6 0 5 kg 23555 00 Remote junction box includes preamplifier 23557 00 10 terminals on 2 16 1 0 kg sensor side and 12 terminals on transmitter side additional two terminals supply power from transmitter to the preamplifier 23557 00 Preamplifier for remote junction box PN 23555 00 1 16 0 5 kg 23550 00 Remote junction box without preamplifier 12 terminals on sensor side and 2 16 1 0 kg 12 terminals on transmitter side 23646 01 Extension cable for connecting transmitter to junction box 10 conductors with 1 Ib per 10 ft 1 internal drain wire cable is terminated and ready for use specify length 1 0 kg per 10 m in feet when ordering 9200273 Extension cable for connecting transmitter to junction box 10 conductors with 1 Ib per 10 ft 1 internal drain wire cable is not terminated customer must prepare cable 1 0 kg per 10 m ends specify length in feet when ordering 2002577 Pipe mounting kit for 2 inch pipe complete includes mounting bracket 2 15 1 0 kg U bolts and all necessary fasteners was model option 07 9241178 00 Stainless s
44. being measured Salt bridges take a variety of forms anything from a glass frit to a wooden plug Salt bridges are highly porous and the pores are filled with ions The ions come from the filling solution and the sample Some bridges permit only diffusion of ions through the junction In other designs a slow outflow of filling solution occurs Migration of ions in the bridge generates a voltage called the liquid junction poten tial The liquid junction potential is in series with the measuring and reference electrode potentials and is part of the overall cell voltage Figure 14 4 helps illustrate how liquid junction poten tials originate The figure shows a section through a pore in the salt bridge For simplicity assume the bridge connects a solution of potassium chloride and hydrochloric acid of equal molar concentration lons from the filling solution and ions from the sample dif fuse through the pores Diffusion is driven by concen tration differences Each ion migrates from where its concentration is high to where its concentration is low Because ions move at different rates a charge sepa ration develops As the charge separation increases electrostatic forces cause the faster moving ions to slow down and the slower moving ions to speed up Eventually the migration rates become equal and the system reaches equilibrium The amount of charge separation at equilibrium determines the liquid junction potential Silver silver chl
45. couple The oxidized form iron 111 can be converted into the reduced form iron Il by the gain of one electron Similarly iron Il can be converted to iron by the loss of an electron For more details concerning the nature of redox potential see Section 14 5 14 3 REFERENCE ELECTRODE As Figure 14 3 shows the reference electrode is a piece of silver wire plated with silver chloride in con tact with a concentrated solution of potassium chlo ride held in a glass or plastic tube In many reference electrodes the solution is an aqueous gel not a liquid The potential of the reference electrode is controlled by the concentration of chloride in the filling solution Because the chloride level is constant the potential of the reference electrode is fixed The potential does change if the temperature changes Platinum internal lead wire Platinum band Test Solution FIGURE 14 2 Measuring Electrode An ORP electrode is a piece of noble metal usual ly platinum but sometimes gold attached to the end of a glass tube The potential of the electrode is controlled by the ratio of oxidized to reduced sub stances in the sample pH and other constituents in the sample may also affect ORP SECTION 14 0 ORP MEASUREMENTS 14 4 LIQUID JUNCTION POTENTIAL A salt bridge see Figure 14 3 is an integral part of the reference electrode It provides the electrical connec tion between the reference electrode and the liquid
46. disables the security feature Press ENTER to save The security code does not become effective until about two minutes after the last keystroke Press EXIT to return to the process display MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 7 BUFFER CALIBRATION PARAMETERS 8 7 1 Purpose This section describes how to do the following 1 activate or deactivate auto calibration 2 identify which buffers will be used during auto calibration 3 setthe stability criteria for auto calibration 8 7 2 Definitions 1 AUTO CALIBRATION In auto calibration screen prompts direct the user through a two point buffer calibration The transmitter recognizes the buffers and uses temperature corrected values in the calibration The transmitter does not accept data until programmed stability limits have been met If auto calibration is deactivated the user must perform a manual calibration In manual calibration the user judges when readings are stable and manually enters buffer val ues The use of auto calibration is strongly recommended 2 BUFFERS Buffers are aqueous solutions to which exactly known pH values have been assigned Assigning a pH value to a buffer involves certain fundamental assumptions Slightly different assumptions lead to slightly different pH scales Over the years various national standards organizations have developed different scales The Model 3081 pH ORP transmitter recognizes the common standard scales as
47. display board is properly oriented The small square window the infrared detector for the remote controller marks the top of the board Insert the three bolts through the holes Align the bolts with the standoffs on the analog board and position the display and CPU boards on the analog board SIf the boards are properly aligned the bolts will drop in place Press along the bottom of the stack to seat the pin and socket connector Tighten the bolts replace the cap and cover lock nut F Mount the transmitter in the desired location Most installations use PN 2002577 pipe mounting bracket RIBBON CABLE INFRARED DETECTOR ANALOG BOARD DISPLAY BOARD FACTORY NSTALLED ON JP5 PIN 4 ONLY PREAMP SELECTION SLIDE SWITCH St SENSOR OR JUNCTION BOX TRANSMITTER FACTORY SET TO TRANSMITTER FRONT COVER FIGURE 1 INITIAL ANALOG PCB SETUP FIGURE 2 F MAJORITY OF COMPONENTS SHOWN FOR CLARITY Section 2 Wiring A Wire sensor Model 3814 55 3854 03 or 396P 01 55 directly to the transmitter as shown in Figure B Wire sensor Model 381 52 3854 04 396 02 55 396P 02 55 or 396R 54 as shown in Figure 4 C Wire the 12 42 4 Vdc power supply to TB 15 4 20 mA and TB 16 4 20 mA MODEL 3081pH ORP MODEL 3081pH ORP TRANSMITTER TRANSMITTER Sam SEE NOTE 2 cr SOL pH jy 90 CUAD oy IN TD IN RTD IN
48. does not reduce the impedance and the sensor is not rebuildable a Try the reference junction rejuvenation procedure described in Section 11 3 b The rejuvenation procedure may not work At best it will get a little more life out of a sensor with a plugged reference c Whether or not the rejuvenation procedure worked go on to step 3 3 Recalibrate the sensor using the auto calibration procedure in Section 7 5 If the sensor can be calibrated a The sensor is in good condition Return it to the process b Change the reference failure high RFH limit to a value about 50 kilohms greater than the measured reference impedance If rEF WARN was also displayed change the reference warning high RWH limit to about 25 kilohms greater than the measured reference impedance If the sensor cannot be calibrated The sensor has failed and must be replaced 94 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 4 4 rEFWArn rEF WArn is an electrode fault message It means the reference electrode impedance exceeds the programmed Reference Warning High RWH limit Ideally when the measurement system exceeds the warning limits the user will have adequate time to diagnose and correct problems before a failure occurs A high reference impedance implies that the liquid junction is plugged or the reference electrolyte is depleted The message also appears if an inappropriate limit has been entered into the transmitter If the measurement sys
49. equal liq uid junction potentials is reasonable In the figure the liquid junction potential of the sample is greater than the buffers The difference gives rise to an error in the measured pH 119 MODEL 3081 pH ORP SECTION 14 0 ORP MEASUREMENTS SECTION 14 0 ORP MEASUREMENTS 14 4 General 14 2 Measuring Electrode 14 3 Reference Electrode 14 4 Liquid Junction Potential 14 5 Relating Cell Voltage to ORP 14 6 ORP Concentration and pH 14 7 Interpreting ORP Measurements 14 8 Calibration TECHNICAL STUFF 14 1 GENERAL Figure 14 1 shows a simplified diagram of an electrochemical cell that can be used to determine the oxidation reduction potential or ORP of a sample The cell consists of a measuring electrode a reference electrode the liq uid being measured and a temperature sensing element The cell voltage is the ORP of the sample In most indus trial and scientific applications a pH meter is used to measure the voltage Because a pH meter is really a high impedance voltmeter it makes an ideal ORP meter Voltmeter Reference Electrode Temperature Sensor Measuring Electrode Test Solution FIGURE 14 1 ORP Measurement Cell The cell consists of a measuring and reference electrode The voltage between the elec trodes is the ORP of the test solution Because ORP depends on temperature the tempera ture at which the measurement is made must be reported Figure 14 1 shows separate measuring and re
50. frit to a wooden plug Salt bridges are highly porous and the pores are filled with ions The ions come from the fill ing solution and the sample Some bridges permit only diffu sion of ions through the junction In other designs a slow outflow of filing solution occurs Migration of ions in the bridge generates a voltage called the liquid junction poten tial The liquid junction potential is in series with the measur ing and reference electrode potentials and is part of the over all cell voltage Silver silver chloride wire Potassium chloride filling solution N Salt bridge FIGURE 13 4 Reference Electrode The fixed concentration of chloride inside the electrode keeps the potential constant A porous plug salt bridge at the bottom of the electrode permits electrical contact between the reference electrode and the test solution Figure 13 5 helps illustrate how liquid junction potentials originate The figure shows a section through a pore in the salt bridge For simplicity assume the bridge connects a solution of potassium chloride and hydrochloric acid of equal molar concentration lons from the filling solution and ions SECTION 13 0 pH MEASUREMENTS from the sample diffuse through the pores Diffusion is driv en by concentration differences Each ion migrates from where its concentration is high to where its concentration is low Because ions move at different rates a charge separa tion develops As the charge se
51. in indus try are low impedance silver silver chlo ride electrodes Every pH and ORP sen sor manufactured by Rosemount Analytical has a low impedance refer ence However there are applications that call for either a high impedance sodi um or pH glass reference electrode Both high impedance and low impedance ref erence electrodes can be used with the Model 3081 pH ORP transmitter High impedance fault 140 kilohms co e 9 o 5 5 2 o o 2 144 5 WARNING AND FAILURE LIMITS FOR 0 THE REFERENCE ELECTRODE NE Warning tells the user that the reference n lt electrode impedance is approaching the failure limit Low and high warning and 20 failure limits are programmable For conventional low impedance silver sil FIGURE 8 2 Suggested Warning and Failure Limits for Low ver chloride reference electrodes only Impedance Reference Electrodes the high limits are useful For high impedance reference electrodes both low and high limits are used The impedance of a typical silver silver chloride reference elec trode is less than 40 kilohms If the impedance is greater than about 140 kilohms the reference electrode has failed Failure is Figure 8 2 shows suggested limits for usually caused by a plugged or coated reference junction or a low impedance reference electrodes depleted electrolyte fill solution gel The reference impedance Figure 8 3 sho
52. no more than 2 C or the pH is between 6 and 8 See Section 13 6 Glass Electrode Slope for more information about errors associated with improper tem perature compensation Manual temperature compensation is useful if the sensor temperature element has failed and a replacement sensor is not available 3 TEMPERATURE ELEMENT pH sensors use a variety of temperature elements The Model 3081 pH transmitter recognizes the following temperature elements and configurations a three and four wire 100 ohm platinum RTDs b three and four wire 1000 ohm platinum RTDs c 3000 ohm Balco RTD A 100 ohm platinum RTD has a resistance of 100 ohms at 0 C A 1000 ohm platinum RTD has a resistance of 1000 ohms at 0 C 3000 ohm Balco RTD Balco is an alloy of 70 nickel and 30 iron has a resistance of 3000 ohms at 25 C Although only two lead wires are necessary to con nect the RTD to the transmitter connecting a third and sometimes fourth wire allows the trans mitter to correct for the resistance of the lead wires and for changes in wire resistance with tem perature The Model 3081 pH ORP transmitter can also be used with a two wire RTD Select a three wire configuration and jumper the RTD return and RTD sense terminals terminals 3 and 4 respec tively MODEL 3081 pH ORP 6 SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS PROGRAM 8 5 3 Procedure 1 Press PROG the infrared remote controller IRC EXIT NEXT
53. pH ORP IN GRAY REFERENCE IN CLEAR REFERENCE SHIELD RED RTD TC IN WHITE RTD TC RETURN WHITE RED RTD SENSE BLUE SOLUTION GROUND FIGURE 3 10 Wire functions for Models 396R 50 396R 54 396R 54 61 396P 02 50 396P 02 54 396P 02 55 385 04 and 385 41 52 MODEL 3081pH ORP TRANSMITTER SEE NOTE 3 RE CLEAR ID WHITE WHITE RED RED CLEAR SENSOR CABLE NOTES PLACE PREAMPLIFIER SELECTION SWITCH S1 IN TRANS MITTER POSITION SEE SECTION 2 2 IF SENSOR HAS 3K BALCO RTD SET JUMPER SECTION 2 2 AND PROGRAM TRANSMITTER TO RECOGNIZE RTD SEC TION 8 5 pH OR 10 5 ORP JUMPER SUPPLIED BY CUSTOMER DO NOT CONNECT BLUE WIRE INSULATE STRIPPED END OF WIRE TO AVOID ACCIDENTAL CONNECTIONS FIGURE 3 11 Wiring diagram for Models 396R 50 396R 54 396R 54 61 396P 02 50 396P 02 54 396P 02 55 385 04 and 385 41 52 Wiring directly to the transmitter 20 SECTION 3 0 WIRING MODEL 3081pH ORP TRANSMITTER SOL pH CND GUARD pH IN EXTENSION CABLE PN 9200273 UNPREPPED OR PN 23646 01 PREPPED CLEAR 1D WHI TE BLACK 182 FARSIDE REMOTE JUNCTION BOX PN 23555 00 OR 5 6 7 8 shonka 82 SENSOR MOUNTED II JUNCTION BOX PN 23709 BOTH INCLUDE PRE AMPL IF IER k JUMPER BOARD PN 23557 00 SEE NOTE 4 ND CONNECTION SENSOR CABLE NOTES PLACE PREAMPLIFIER SELECTION SWITCH S1 IN SEN SOR JUNCTION BOX POSITION SEE SECTION
54. pic tured above left At the CALIbrAtE sub menu press ENTER The CAL bF1 prompt appears Rinse the sensor and place it in the first buffer Be sure the glass bulb and the temperature element are completely submerged Keep the sensor tip at least three inches below the liquid level Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbles The main display will show the measured pH based on the previous calibration Press ENTER bF1 flashes until the measured pH meets the programmed stability limits If the pH reading is not stable after 20 minutes the transmitter automatically leaves the CALIBRATE menu and returns to the process mode If this happens consult Section 12 5 Troubleshooting for assis tance Once the reading is stable the display changes to look like the figure at the left The flashing number is the nominal pH that is the pH of the buffer at 25 C If the flashing number does not match the nominal pH press M or until the correct pH appears Press ENTER to save the first calibration point The CAL bF2 prompt appears At the CAL bF2 prompt remove the sensor from the first buffer Rinse the sensor and place it in the sec ond buffer Be sure the glass bulb and the temperature element are completely submerged Keep the sensor tip at least three inches below the liquid level Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbl
55. proportional to the concentration or activity of the substance of interest A menu contains the steps that allows the user to calibrate or program the Model 3081pH ORP transmitter or to read diagnostic messages Molar concentration is the number of moles of substance dissolved in one liter of solution A mole is a measure of the quantity of ions molecules or atoms in a sub stance The Nernst equation relates the potential of an electrode to the concentration or activity of the chemical substances that appear in the half reaction occurring at the electrode A non incendive circuit is a circuit that is incapable of igniting a mixture of an explosive gas in air under normal operating conditions The gases used in the test are the same gases used for intrinsically safe testing ORP is oxidation reduction potential It is the tendency of a chemical species to gain or lose electrons at a noble metal electrode ORP is usually measured in mil livolts The type of measuring electrode the type of reference electrode and the temperature must be identified when stating the ORP of a sample Oxidation is the loss of electrons For example when iron II ion becomes iron III ion it is loses an electron Fe Fe 3 131 MODEL 3081 pH ORP pH Platinum electrode Platinum RTD Preamplifier Process display Prompt Reduction Reference electrode Reference impedance Reference offset Reset RTD Salt b
56. ratio in the Nernst equation also includes hydrogen ions the ORP of a mixture of chromium VI and chromium III is a function of pH To appreciate the extent to which pH influences ORP consider the conversion of chromium VI to chromium I In acidic solution the half reaction is Cr 07 14 H 6 e 2 C3 7 H2O 3 e Chromium VI exists as dichromate Cr2O72 acidic solution 123 MODEL 3081 pH ORP The Nernst equation for reaction 3 is 0 1987 t 273 15 Cr 3 2 9 s 6 O Note that the hydrogen ion factor in the concentration ratio is raised to the fourteenth power The table shows the expected effect of changing pH on the measured ORP at 25 C pH changes ORP changes by from 2 0 to 2 2 from 2 0 to 2 4 from 2 0 to 1 8 from 2 0 to 1 6 The Nernst equation can be written for any half reaction However not all half reactions behave exactly as predict ed by the Nernst equation Why real systems do not act as expected is beyond the scope of this discussion The potential of chromium VI chromium III couple used as an example above does not perfectly obey the Nernst equation However the statement that pH has a strong effect on the electrode potential of the couple is true As mentioned earlier ORP is best suited for measur ing changes not absolute concentrations If ORP is used to determine concentration great care should be exercised An example is the dete
57. respectively There are several ways of defining the standard electrode potential E No matter which defi nition is used the standard electrode potential is sim ply the electrode potential when the concentrations of iron II and iron III have defined standard values Equation 2 shows that the electrode potential is con trolled by the logarithm of the ratio of the concentration of iron 1 to iron III Therefore at 25 C if the ratio changes by a factor of ten the electrode potential changes by 0 1987 25 273 15 1 log 10 59 2 mV As the expression above shows the voltage change is also directly proportional to temperature and inversely proportional to the number of electrons transferred 14 7 INTERPRETING ORP MEASUREMENTS Interpreting ORP and changes in ORP requires great caution There are several concepts to keep in mind concerning industrial ORP measurements ORP is best used to track changes in concentration or to detect the presence or absence of certain chemicals For example in the treatment of wastes from metal fin ishing plants chromium VI is converted to chromium III by treatment with sulfur dioxide Because chromium VI and chromium III are a redox couple ORP can be used to monitor the reaction As sulfur dioxide converts chromium VI to chromium 1 the concentration ratio changes and the ORP drops Once all the chromium VI has been converted to chromium III and a slight excess
58. see Section 8 5 NO Transmitter problem 2 Clean sensor amp re test it 1 Replace Analog CPU board stack 3 If problem persists rebuild or PN 23574 02 replace the sensor Transmitter test OK FIGURE 12 5 Troubleshooting Flow Chart Preamplifier in Sensor Mounted Junction Box or Remote Junction Box MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING pH measurement problem Perform buffer calibration outside of the process Refer to Section 7 5 Buffer calibration Likely Process Problem OK or Ground Loop 1 Measure pH of a grab sample in a beaker If pH is correct then the process is OK Resolve the ground loop insu late shield wires from grounded metal See Section 12 5 8 s internal preamplifie Place transmitter internal pream switch in transmitter in Ground un grounded processes plifier switch in proper position correct position See example all plastic piping Simulate pH directly into the trans mitter Refer to Section 12 8 2 Transmitter problem Replace Analog CPU board Analyzer test OK Likely Sensor Problem stack PN 23574 02 1 Verify sensor is compatible with the analyzer Must have PT100 PT1000 or 3K Balco RTD Verify RTD jumpers and temperature parameter programming Check RTD If bad or wrong use manual temperature compensa tion see Section 8 5 2 Clean sensor amp re test it 3 If problem persists rebuild or replace the sensor FIGURE 12
59. sensor or j box position afterwards See Section 2 2 the error message clears the remote preamplifier is faulty Replace the preamplifier If the error message remains the sensor has failed Replace the sensor 98 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 4 9 SLOPE Err LO SLOPE Err LO means that a two point buffer calibration attempt has failed The slope is too low 40 mV pH for a good measurement Troubleshooting Flowchart SLOPE Err LO A Repeat the calibration 1 Inaccurate buffers can cause a low slope Repeat the calibration using fresh buffers Alkaline buffers pH 10 or greater are particularly susceptible to changing value in air or with age If a high pH buffer was used in the failed calibration try a lower pH buffer when repeating the calibration For example use pH 4 and 7 buffer instead of pH 7 and 10 buffer Allow adequate time for readings in buffer to become constant If the sensor was in a process substantially colder or hotter than the buffer allow at least 20 minutes for readings in the buffer to stabilize Alternatively place the sensor in a container of water at ambient temperature for 20 minutes before starting the calibration Be sure the correct buffer values are being entered during calibration If the second calibration was successful an error was made during the first attempt If the second calibration fails go to step B B Refer to the wiring diagrams in Section 3 0 and check
60. solutions having pH outside the normal range of the process To prevent false alarms and possible unde sired operation of chemical dosing pumps place the analyzer in hold during EAHIBRATE calibration See Section 7 3 Using the Hold Function for details CALIbrAtE EXIT NEXT ENTER 7 6 3 Procedure 1 Before starting refer to Section 8 7 Buffer Calibration Parameters to deactivate auto cali bration Enter the CALIBRATE menu by pressing CAL the IRC The CALIbrAtE sub menu CALIBRATE appears pictured above left CAL 1 Atthe CALIbrAtE sub menu press ENTER The CAL bF1 prompt appears NEXT ENTER 4 Rinse the sensor with deionized water and place it in the first buffer along with a calibrated thermometer Submerge the sensor tip at least three inches below the liquid level Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbles The main display will show the measured pH based on the previous calibration CALIBRATE Once the pH reading and temperature are stable press ENTER The display changes to the CAL Screen shown at the left Use the editing keys to change the flashing display to the pH value EXIT of the buffer at the measurement temperature Press ENTER to save the value as buffer bF1 The transmitter expects a reading to be entered within 20 minutes after the CAL bF1 prompt appears If ENTER is not pressed the transmitter leaves the CALI
61. the results Also note the reference offset and the slope Return the sensor to service Check the sensor again after a period shorter than the one originally selected For example if the first interval was two weeks repeat the check after one week 6 After a while it will become apparent how long the sensor holds calibration The minimum calibration frequency can then be determined 7 Check the calibration of the sensor at least several times during the regular calibration interval Interim checks verify the sensor is still in calibration and validate the process measurements made since the last calibration or calibration check 88 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING SECTION 12 0 TROUBLESHOOTING 12 1 WARNING AND FAULT MESSAGES 12 2 CALIBRATION ERRORS 12 3 TROUBLESHOOTING GENERAL 12 4 TROUBLESHOOTING WHEN A DIAGNOSTIC MESSAGE IS SHOWING 12 5 TROUBLESHOOTING WHEN NO DIAGNOSTIC MESSAGE IS SHOWING 12 66 SYSTEMATIC TROUBLESHOOTING 12 7 DISPLAYING DIAGNOSTIC VARIABLES 12 8 TESTING THE TRANSMITTER BY SIMULATING pH 12 9 FACTORY ASSISTANCE AND REPAIRS 12 1 WARNING AND FAULT MESSAGES The Model 3081 pH ORP transmitter continuously monitors the measurement loop sensor and transmitter for conditions that cause erroneous measurements When a problem occurs the transmitter displays either a warning or fault mes sage A warning alerts the user that a potentially system disabling condition exists If the condition cau
62. the same temperature as the process However great care must be exercised when the buffer temperature is significantly greater than ambient tempera ture First the buffer solution must be protected from evap oration Evaporation changes the concentration of the buffer and its pH Above 50 C a reflux condenser may be necessary Second the pH of buffers is defined over a lim ited temperature range For example if the buffer pH is defined only to 60 C the buffer cannot be used for calibra tion at 70 C Finally no matter what the temperature it is important that the entire measurement cell sensor and solution be at constant temperature This requirement is critical because lack of temperature uniformity in the cell is one reason the cell isopotential point moves when the tem perature changes 13 9 JUNCTION POTENTIAL MISMATCH Although glass electrodes are always calibrated with buffers the use of buffers causes a fundamental error in the measurement When the glass and reference electrodes are placed in a buffer a liquid junction potential develops at the inter face between the buffer and the sall bridge The liquid junc tion potential is part of the overall cell voltage and is includ ed in A in equation 2 Equation 2 can be modified to show Ej as a separate term E A Ej B t 273 15 7 3 or E E pH t Ej 4 where E pH t A B t 273 15 pH 7 In Figure 13 8 calibration and
63. the sensor 3 in a remote junction box 4 atthe transmitter Figure 3 1 illustrates the various arrangements transmitter transmitter sensor b preamplifier transmitter c junction box preamplifier sensor d FIGURE 3 1 Wiring and Preamplifier Configurations for pH and ORP Sensors junction box transmitter transmitter preamplifier e sensor The asterisk identifies the location of the preamplifier In a and b the sensor is wired directly to the transmitter The signal is amplified at the sensor a or at the transmitter b In c the sensor is wired through a sensor mounted junction box to the trans mitter The preamplifier is in the sensor mounted junction box In d and e the sensor is wired through a remote junction box to the transmitter The preamplifier is located in the sensor d or the junction box e MODEL 3081 pH ORP SECTION 3 0 WIRING 3 2 WIRING DIAGRAMS FOR pH and ORP SENSORS Refer to Tables 3 1 through 3 12 to locate the appropriate wire function and wiring diagram There is a separate table for each model The sensor models having the highest number appear first If you do not know the model number of the sensor refer to the flow charts on pages 28 through 30 Only the model option numbers needed to select the cor rect wiring diagram are shown Other numbers are not shown For all other sensors see sensor manual Table 3 1 Wiring Diagrams for Model 399 sensors
64. the setting by 20 Thus a setting of 140 means that following a step change the output takes about seven minutes to reach 95 of final reading The output dampen setting does not affect the response time of the process dis play The maximum setting is 255 MODEL 3081 pH ORP NEXT ENTER SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 3 3 Procedure 1 2 Enter the Program menu by pressing PROG on the IRC The OutPut sub menu appears Press ENTER The screen displays the 4 MA prompt Use the editing keys to change the displayed number to the desired pH The allowed range is 0 00 to 14 00 Press ENTER to save The screen displays the 20 MA prompt Use the editing keys to change the displayed number to the desired pH The allowed range is 0 00 to 14 00 Press ENTER to save The screen displays the HoLd prompt Use the editing keys to change the display to the output desired when the transmitter is in hold The range is 3 80 to 22 00 mA Entering 00 00 causes the transmitter to hold the output at the value it was when placed in hold The hold setting overrides the fault setting Press ENTER to save The screen displays the FAULt prompt Use the editing keys to change the display to the output desired when the transmitter detects a fault The range is 3 80 to 22 00 mA Entering 00 00 causes the transmitter to hold the output at the value it was when the fault occurred Press ENTER to save The screen displays the dPn prompt Us
65. will appear Use the arrow keys to change the displayed number to the desired pH Press ENTER to save Press RESET to return to the process display QUICK REFERENCE GUIDE MODEL 3081PH ORP Automatic Buffer Calibration Note A pH measurement is only as good as the calibration and the calibration is only as good as the buffers used For best results calibrate with buffers having the same temperature as the process Allow time for the sensor and buffers to reach the same temperature If the process temperature is more than 10 C different from the buffer allow at least 20 minutes Be careful using buffers at high temperatures The pH of many buffers is undefined above 60 C See the main instruction manual for fur ther information A Aim the infrared remote controller IRC at the LCD display Press HOLD on the IRC HoLd OFF will appear Press to toggle the display to HoLd On Press ENTER to engage hold mode The HOLD indicator will appear to the left of the pH value B Press CAL CALIbrAtE will appear Press ENTER CAL bF1 will appear C With the sensor in the first buffer be sure the glass bulb and the temperature element are completely submerged about 3 inches deep Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbles Press ENTER bF1 will flash until reading is stable The measured pH value will appear in the main display Press or until the small number next bF 1 mat
66. wiring Connections to TB 10 TB 7 and 8 are particularly important Recalibrate the sensor using the auto calibration procedure in Section 7 5 If wiring was the only problem the sensor should calibrate If the message persists go to step C C Inspect and clean the sensor See Section 11 3 Recalibrate the sensor using the auto calibration procedure in Section 7 5 If the sensor was dirty it should calibrate after cleaning If the message persists go to step D D Check for a faulty sensor If a spare sensor is available connect it to the transmitter Use the auto calibration procedure in Section 7 5 to calibrate the sensor t the new sensor cannot be calibrated the transmitter is faulty Go to step E If the new sensor can be calibrated the old sensor has failed If a spare sensor is not available measure the glass impedance GIMP See Section 12 7 If the glass impedance is less than about 20 megohms the glass has cracked and the electrode must be replaced If the glass impedance is greater than about 20 megohms the sensor is probably in good condition Go to step E E Check transmitter performance by simulating pH inputs See Section 12 8 If the transmitter performs satisfactorily go to step F If the transmitter does not respond to simulated inputs replace the board stack PN 23574 02 F If the transmitter responds to simulated inputs the problem must lie with the sensor or the interconnecting wiring
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68. 00 10 ees ShoW FLt 1 SLOPE 59 01 pag OutPut dIAGnOStIC tEMP dISPLAY bUFFEr ISOPOtntAL SIM OUtPUt bF 2 I 4 MA 00 00 rOFFSt 060 tAUIO On PH On tCOEF 00 00 tESt 12 00 bF2 10 01 I 1 20 14 00 OFF tMAn 25 0 tEMP C bUFFEr Std ISO 07 00 f o HoLd 21 00 IMPIC ON tC 100 3 OUtPUt Cur 10 Snr 07 00 I I I FAULt 22 00 GFH 1500 COdE 000 PH 00 02 I dPn 0 00 GWH 1000 GWL 020 GFL 010 l CAL 000 rEF LO rFH 140 TWH 040 rWL 000 rFL 000 Technical Support Hotline For assistance with technical problems please call the Customer Support Center CSC The CSC is staffed from 5 00am to 5 00pm PST Phone US only 800 854 8257 Phone 949 757 8500 Fax 949 863 9159 World Wide Web www raihome com Menu Tree for pH MODEL 3081 pH ORP TABLE OF CONTENTS MODEL 3081 PH ORP MICROPROCESSOR TRANSMITTER TABLE OF CONTENTS Section Title Page 1 0 DESCRIPTION AND SPECIFICATIONS u 1 1 gir Y 1 1 2 ni
69. 1 Measure the voltage The measured voltage should be 0 mV and the pH should be approximately 7 Because the calibration data in the transmitter may be offsetting the input voltage the displayed pH may not be exactly 7 0 If the actual readings are close to expected the transmitter is probably working fine 12 If a standard millivolt source is available use it to perform a simulated calibration 13 Remove the jumper used to connect the reference pin to the center pin of the BNC Connect the negative terminal of the standard millivolt source to the reference pin and connect the positive terminal to the center pin of the BNC DO NOT LET THE WIRE TOUCH THE OUTSIDE OF THE BNC CONNECTOR 14 Following the auto calibration procedure in Section 7 5 calibrate the transmitter Use 0 0 mV for pH 7 bF1 and 177 4 mV for pH 10 bF2 If the transmitter is working it should accept the calibration 15 To check linearity leave autocalibration and return to the main display Set the voltage source to the values in the table and verify that the pH reading matches the expected value Voltage mV 12 8 5 pH Simulation When Preamplifier is in Sensor The preamplifier the sensor simply converts the high impedence signal into a low impedance signal without amplifying it To simulate pH values use the procedure in Section 12 8 3 12 9 FACTORY ASSISTANCE AND REPAIRS 12 9 1 Troubleshooting Assistance For assistance in correcting transmitter sens
70. 1 81 32078 2 310N 339 8 188 8 122 5 33871 335 1 84 30018 TNIW831 30A p o AlddhS S d 83121234580 2 310N 335 8 134 5 378V 310N 335 1 81 0078 WNENYSL Qvo 9 td 3 Q 2 8 v 580089 NOISIAIQO 11 til ssw 20A b Z V3uV SHOQuVZVH A dans 33 03 0314123d5Nn v3uv 3375 2 310N 335 U3IUUVS A134VS 94 AC 181 soo 60 oE 12 o3 xud SPA XDUA 91 Si L STVNIW831 TVNOIS 98 5 Su3 3WNVUYd ALIIN3 1806 114142530 993 NOISIAH 831412346 3S14H3HIO SS3TND 5310 2 30 2 I33HS NO 5310 111 318V1 3 10N 335 AWG 1 SSYTO NI 350 30V JU3iNI 1 310N3H 310N 335 OMY 03013195 SIYIN P SIC T3QOW INPORGSD 318 2 O30N3 WDO3U 378Vl 310N 335 ANNO V3HY 55972 NI 35 32Y JH3lNT UALLINSNVEL 310W3H 00 19582 3dAl GLZ INhOW3SOB diV3ud Hd EIIE 31891 b 310N 335 ANO V38V 5913 NI JSN 03 30VJE3INI diO Hd 1806 H3iiIlWSNVHUL 310W3H S4 1300 INfOW3SOH 6 33S 72 SGT3IHS 2 ONGI OL 1 0 9 9 2 Nd 3dd3HdNfl 5220026 Nd SOS 31929 G30N3 WOJ38 111 308v ONY 310N 335 A NO 1 5512 0
71. 2 2 IF SENSOR HAS 3K BALCO RTD SET JUMPER SECTION 2 2 AND PROGRAM TRANSMITTER TO RECOGNIZE RTD SEC TION 8 5 pH OR 10 5 ORP SEE FIGURE 3 24 FOR TERMINATION OF RAW INTERCON NECTING CABLE PN 92002723 JUMPER SUPPLIED BY CUSTOMER DO NOT CONNECT BLUE WIRE INSULATE STRIPPED END OF WIRE TO AVOID ACCIDENTAL CONNECTIONS FIGURE 3 12 Wiring diagram for Models 396R 50 396R 54 396R 54 61 396P 02 50 396P 02 54 396P 02 55 385 04 and 385 41 52 Wiring through a sensor mounted junction box to the transmitter MODEL 3081 pH ORP SECTION 3 0 WIRING CLEAR INNER DRAIN WHITE RTD TC RETURN WHITE RED RTD SENSE RED RTD TC IN WHITE GRAY REFERENCE SHIELD GRAY REFERENCE IN BLUE SOLUTION GROUND WHITE BLACK pH ORP SHIELD BLACK pH mV IN BROWN PREAMP 5 V GREEN PREAMP 45 V FIGURE 3 13 Wire functions for Models 396P 01 55 385 03 381 40 55 381 43 55 MODEL 3081pH ORP TRANSMITTER SOL pH e TEM lt Z or SENSOR CABLE NOTES 1 PLACE PREAMPLIFIER SELECTION SWITCH 51 SENSOR JUNCTION BOX POSITION SEE SECTION 2 2 2 TO EXTEND CABLE LENGTH USE JUNCTION BOX PN 23550 00 WITH EXTENSION CABLE PN 23646 01 FINISHED OR PN 9200273 UNFINISHED WIRE THROUGH TERMINALS POINT TO POINT SEE FIGURE 3 24 FOR TERMINATION OF RAW CABLE PN 9200273 FIGURE 3 14 Wiring diagram for Models 396P 01 55 385 03 381 40 55 and 381
72. 30 Vdc terminal voltage when the output signal is 22 mA Operating Region 9 E lt The power supply must provide a surge current Without HART Communication during the first 80 milliseconds of start up For a 42 4 Vde 24 Vdc power supply and a 250 ohm load resistor 18 24 30 36 42 maximum the surge current is 40 mA For all other supply Power supply voltage Vdc voltage and resistance combinations the surge current is not expected to exceed 70 mA For digital HART or AMS communications the load must be at least 250 ohms To supply the 12 5 Vdc lift off voltage at the transmitter the power sup ply voltage must be at least 18 Vdc FIGURE 2 6 Load Power Supply Requirements For intrinsically safe operation the supply voltage should not exceed 42 4 Vdc 2 5 2 Power Supply Current Loop AT POWER SUPPLY Wiring Refer to Figure 2 7 TERMINAL BLOCK REAR COVER Run the power signal wiring through OMITTED ee S the opening nearest terminals 15 and TO EARTH GROUND 16 Use shielded cable and ground the shield at the power supply To ground the transmitter attach the shield to the grounding screw on the inside of the Ot transmitter case A third wire can also NN 7 be used to connect the transmitter CABLE IN z 12 5 42 4 VDC case to earth ground NOTE For optimum EMI RFI immunity the power sup L EARTH GROUND ply output cable
73. 6 Troubleshooting Flow Chart Preamplifier in Transmitter or Built into Sensor 109 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 7 DISPLAYING DIAGNOSTIC VARIABLES 12 7 1 Purpose This section describes how to display the diagnostic variables listed below DIAGNOSTIC MEASUREMENTS DIAGNOSTIC MESSAGES 1 Sensor voltage in mV InPut 1 Software version VEr 2 Glass impedance in megohms GIMP 2 Display last three fault messages ShoW FLt 3 Reference impedance in kilohms 4 Temperature in C tEMP For high impedance reference electrodes the reference impedance is in megohms For an explanation of the meaning of diagnostic messages refer to Section 8 4 Displays are read only 12 7 2 Procedure 1 Enter the Diagnostic menu by pressing DIAG on the IRC Sensor voltage in mV InPut appears 2 Press NEXT The temperature corrected glass impedance in megohms GIMP appears 3 Press NEXT The reference impedance appears For conventional low impedance silver silver chloride reference electrodes the reference impedance has units of kilohms For the rare occasions when a high impedance reference is used the units are megohms See Sections 8 4 for pH and 10 4 for ORP for more information Press NEXT The model number and software version Ver appears Press NEXT The temperature tEMP measured by the sensor appears Press NEXT ShoW sub menu appears Press ENTER The most r
74. 9 AIG 55 79 11806 Y 21806 dHO Hd LOE 1300 4 315 5 NOILVTIVISNI 300Bd NOISO iJ3X3 03 0842 WA OQIIVW3HOS 031312395 3siMu3Hi0 5537 S310N LIMQNOD NI 311 15 1 38 ISDN 3789 HOSN3S ONY 3809 TIV wavy 0907 H 0907 BOSN3S ONOI 12 1 02 9920025 Nd HOSN3S 0 02 7 010801 804 9220026 Nd 338V5 Q30N3W4D23H 719010501 so ONT LIViNGO HOSN3S ONDD 4557 05435 305435 Raviy ovol 8520026 Nd NI dHO Hd NI ANY 38d 22 38IM 2 318 2 Q30N3 AWOO3H 3275 Qasn AHLIfIHID 1VH931NI SnoQHvzvH 8520026 Nd 9n X vl 318 2 Q30N3 WC 3J uDSN3S WDAIXVM 1334 Sk XVDOD HOSN3S 18 12 10 480 4 1806 1140 T3004 18 2 v3uv 3375 iunaueson 6350002 QUA 6504 400 S DUD iDOMi DUV OL ADDE DO PJU 81163000 S 36 MODEL 3081 pH ORP SECTION 5 0 OPERATION WITH REMOTE CONTROLLER SECTION 5 0 OPERATION WITH REMOTE CONTROLLER 5 1 Displays 5 2 Infrared Remote Controller IRC Key Functions 5 3 Menu Tree pH 5 4 Diagnostic Messages pH 5 5 Menu Tree ORP 5 6 Diagnostic Message
75. ANSMITTER TO RECOGNIZE RTD SECTION 8 5 pH OR 10 5 ORP 3 JUMPERS SUPPLIED BY CUSTOMER FIGURE 3 4 Wiring diagram for Models 399 02 399 09 381pHE 30 41 and 381pHE 31 41 after removing BNC and terminating cable Wiring Diagram for Models 399 09 62 381pHE 30 42 and 381pHE 31 42 as received Wiring directly to the transmitter INCLUDES PREAMPLIFIER REMOTE JUNCTION BOX SECTION 3 0 WIRING MODEL 3081pH ORP TRANSMITTER SOL pH GND GUA RTD SHIELD EARTH GND BLACK BROWN GREEN EXTENSION CABLE PN 9200273 UNPREPPED OR DR PN 23646 01 PREPPED WHITE BLACK TB2 PN 23555 00 PN 23557 00 TB1 NO CONNECTION i SENSOR CABLE NOTES 1 PLACE PREAMPLIFIER SELECTION SWITCH 51 SENSOR JUNCTION BOX POSITION SEE SEC TION 2 2 IF SENSOR HAS 3K BALCO RTD SET JUMPER SECTION 2 2 AND PROGRAM TRANSMITTER TO RECOGNIZE RTD SECTION 8 5 pH OR 10 5 ORP SEE FIGURE 3 24 FOR TERMINATION OF RAW INTERCONNECTING CABLE PN 9200273 JUMPERS SUPPLIED BY CUSTOMER FIGURE 3 5 Wiring diagram for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 after removing BNC and terminating cable Wiring Diagram for 399 09 62 381pH 30 42 and 381pH 31 42 as received Wiring through a remote junction box to the transmitter MODEL 3081 pH ORP CLEAR EARTH
76. BRATE menu and returns to the process mode CALIBRATE At the CAL bF2 prompt remove the sensor from the first buffer Rinse the sensor and ther CAL bF mometer with deionized water and place them the second buffer Submerge the sensor tip NEXT at least three inches below the liquid level Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbles The main display will show the measured pH based on the previous calibration Once the pH reading and temperature are stable press ENTER The display changes to the Screen shown at the left Use the editing keys to change the flashing display to the pH value of the buffer at the measurement temperature Press ENTER to save the value as buffer bF 2 The transmitter expects a reading to be entered within 20 minutes after the CAL bF2 prompt appears If ENTER is not pressed the transmitter leaves the CALIBRATE menu and returns to the process mode 8 The calibration is complete but the transmitter remains in the CALibrATE sub menu for two minutes after ENTER is pressed 9 Remove the sensor from the buffer and return it to the process If the transmitter was in hold during calibration wait until readings have stabilized before taking the transmitter out of hold 10 The transmitter uses the calibration data to calculate a new slope Refer to Section 13 7 Buffers and Calibration for more details If the slope is unacceptable the calibration w
77. CO RTD SET JUMPER SECTION 2 2 AND PROGRAM TRANSMITTER TO RECOGNIZE RTD SECTION 8 5 pH OR 10 5 ORP 3 JUMPERS SUPPLIED BY CUSTOMER FIGURE 3 8 Wiring diagram for Models 397 50 397 54 396 50 396 54 389 02 50 and 389 02 54 after removing BNC and termi nating cable Wiring diagram for Models 397 54 62 396 54 62 and 389 02 54 62 as received Wiring directly to the transmitter SECTION 3 0 WIRING MODEL 3081pH ORP TRANSMITTER SOL pH GND GUARD EXTENSION CABLE PN 9200273 UNPREPPED OR OR PN 23646 01 PREPPED 180 FARSIDE REMOTE JUNCTION BOX PN 23555 00 BL CINCLUDES PREAMPLIFIER BOARD PN 23557 00 BNC NO CONNECTION JUMPER SEE NOTE 4 SENSOR CABLE NOTES PLACE PREAMPLIFIER SELECTION SWITCH S1 IN SEN SOR JUNCTION BOX POSITION SEE SECTION 2 2 IF SENSOR HAS 3K BALCO RTD SET JUMPER SECTION 2 2 AND PROGRAM TRANSMITTER TO RECOGNIZE RTD SECTION 8 5 pH OR 10 5 ORP SEE FIGURE 3 24 FOR TERMINATION OF RAW INTERCONNECTING CABLE PN 9200273 JUMPERS SUPPLIED BY CUSTOMER FIGURE 3 9 Wiring diagram for Models 397 50 397 54 396 50 396R 50 60 396R 54 60 396 54 389 02 50 and 389 02 54 after removing BNC and terminating cable Wiring diagram for Models 397 54 62 396 54 62 and 389 02 54 62 as received Wiring through a remote junction box to the transmitter MODEL 3081 pH ORP CLEAR INNER DRAIN CLEAR pH ORP SHIELD ORANGE
78. Call Rosemount Analytical for authorization 2 To verify warranty supply the factory sales order number or the original purchase order number In the case of individual parts or sub assemblies the serial number on the unit must be supplied 3 Carefully package the materials and enclose your Letter of Transmittal see Warranty If possible pack the materials in the same manner as they were received 4 Send the package prepaid to Rosemount Analytical Inc Uniloc Division Uniloc Division 2400 Barranca Parkway Irvine CA 92606 Attn Factory Repair RMA No Mark the package Returned for Repair Model _ 134 17 3 NON WARRANTY REPAIR The following is the procedure for returning for repair instruments that are no longer under warranty 1 Call Rosemount Analytical for authorization 2 Supply the purchase order number and make sure to provide the name and telephone number of the individual to be contacted should additional information be needed 3 Do Steps 3 and 4 of Section 17 2 NOTE Consult the factory for additional informa tion regarding service or repair WARRANTY Goods and part s excluding consumables manufactured by Seller are warranted to be free from defects in workman ship and material under normal use and service for a period of twelve 12 months from the date of shipment by Seller Consumables pH electrodes membranes liquid junctions electrolyte O rings etc are warranted to
79. ENTER 2 Press NEXT until the tEMP sub menu appears the display Press ENTER 4 3 The screen displays the tAUTO prompt Press or to enable On or disable OFF automatic temperature compensation Press ENTER to save 4 tMAN prompt appears Use the editing keys to change the temperature to the desired value To enter a negative number press 3 until no digit is flashing Then press or to display the negative sign Permitted values are between 5 0 130 0 C If tAUTO was disabled in step 3 the temperature entered in this step will be used in all subsequent measurements no matter what the process tempera ture is Press ENTER to save The screen shows the tC prompt Press or v to scroll to the desired temperature element and wiring configuration Press ENTER to save 3 wire 1000 ohm RTD 4 wire 1000 ohm RTD 3 wire 100 ohm RTD 4 wire 100 ohm RTD 3000 ohm Balco RTD NOTE A jumper on the analog board must also be set to match RTD See Section 2 2 Pre Installation Set Up Press EXIT to return to the process display 65 MODEL 3081 pH ORP PROGRAM dISPLAY EXIT 66 NEXT ENTER SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 6 DISPLAY UNITS 8 6 1 Purpose This section describes how to do the following 1 2 3 4 Switch the process display units between pH and ORP millivolts select C or F for the temperature display select percen
80. GROUND BNC REFERENCE N AND pH mV IN CLEAR RTD TC SHIELD WHITE RTD TC IN RED RTD SENSE REMOVE BNC AND TERMINATE COAXIAL CABLE BEFORE WIRING SENSOR TO TRANSMITTER SEE FIGURE 3 23 ALTERNATIVELY USE A BNC ADAPTER PN 9120531 OR ORDER MODEL OPTION 62 SENSOR WITH BNC REMOVED AND TERMINATIONS COMPATIBLE WITH 3081 pH ORP IF USING A BNC ADAPTER THE RED WIRE IS MV OR pH IN AND THE BLACK WIRE IS REFERENCE IN TO PREVENT SHORT CIRCUITS TO THE TRANSMITTER HOUSING INSULATE THE BNC WITH BY WRAPPING IT WITH ELECTRICAL TAPE FIGURE 3 6 Wire functions for Models 397 50 397 54 396 50 396 54 396R 50 60 396R 54 60 389 02 50 and 389 02 54 before removing BNC and terminating cable CLEAR EARTH GROUND CLEAR REFERENCE IN ORANCE pH mV IN RED RTD SENSE WHITE RTD TC IN CLEAR RTD TC SHIELD IF USING A BNC ADAPTER THE RED WIRE IS MV OR pH IN AND THE BLACK WIRE IS REFERENCE IN TO PREVENT SHORT CIRCUITS TO THE TRANSMITTER HOUSING INSULATE THE BNC WITH BY WRAPPING IT WITH ELECTRICAL TAPE FIGURE 3 7 Wire functions for Models 397 50 397 54 396 50 396 54 396R 50 60 396R 54 60 389 02 50 and 389 02 54 after removing BNC and terminating cable Wire functions for Models 397 54 62 396 54 62 and 389 02 54 62 as received MODEL 3081pH ORP TRANSMITTER pH GND GUARD SENSOR CABLE NOTES 1 PLACE PREAMPLIFIER SELECTION SWITCH 51 IN TRANSMITTER POSITION SEE SECTION 2 2 2 IF SENSOR HAS 3K BAL
81. H changes The layer of glass between the two hydrated layers remains dry The dry layer makes the glass a poor conductor of electricity and causes the high internal resistance several hundred megohms typical of glass electrodes 13 3 REFERENCE ELECTRODE As Figure 13 4 shows the reference electrode is a piece of silver wire plated with silver chloride in contact with a con centrated solution of potassium chloride held in a glass or plastic tube In many reference electrodes the solution is an aqueous gel not a liquid Like the electrode inside the glass electrode the potential of the external reference is controlled by the concentration of chloride in the filling solu tion Because the chloride level is constant the potential of the reference electrode is fixed The potential does change if the temperature changes Electrode Sample Internals Glass Membrane Hydrated Layer FIGURE 13 3 Cross Section through the pH Glass For the glass electrode to work the glass must be hyarat ed An ion exchange mechanism involving alkalai metals and hydrogen ions in the hydrated layer is responsible for the pH response of the glass 115 MODEL 3081 pH ORP 13 4 LIQUID JUNCTION POTENTIAL The salt bridge see Figure 13 4 is an integral part of the ref erence electrode It provides the electrical connection between the reference electrode and the liquid being meas ured Salt bridges take a variety of forms anything from a glass
82. ID Resistance Values nri ee dem eene Rn 96 vi MODEL 3081 pH ORP SECTION 1 0 DESCRIPTION AND SPECIFICATIONS SECTION 1 0 DESCRIPTION AND SPECIFICATIONS 1 14 Features 1 2 Accessories 1 3 Specifications General for Model 3081 pH ORP 1 4 Specifications pH 1 5 Specifications ORP 1 6 Ordering Information CHANGING FROM pH TO ORP operation takes only seconds REMOTE COMMUNICATION IS SIMPLE use the hand held infrared remote controller or any HART compatible device e LARGE TWO LINE DISPLAY shows pH ORP temperature and output signal SIMPLE INTUITIVE MENUS make programming and calibrating easy AUTOMATIC TWO POINT BUFFER CALIBRATION reduces errors SOLUTION TEMPERATURE COMPENSATION converts measured pH to the pH at 25 C CONTINUOUS DIAGNOSTICS monitor sensor performance and warn the user of failure FAULT or approaching failure WARNING ROBUST NEMA 4X ENCLOSURE protects the transmitter from harsh plant environments INTRINSICALLY SAFE DESIGN allows the transmitter to be used in hazardous environments with appropriate safety barriers NON VOLATILE EEPROM MEMORY retains program settings and calibration data during power failures 1 1 FEATURES APPLICATION The Model 3081pH ORP Transmitter with the appropriate pH or ORP sensor measures pH between 0 and 14 and ORP between 1400 and 1400 millivolts Converting the transmitter from a pH instru ment to an ORP instrume
83. Instruction Manual PN 51 3081pH rev D August 2002 Model 3081 pH ORP Smart Two Wire Microprocessor Transmitter ROSEMOUNT Analytical 5 Process Management ESSENTIAL INSTRUCTIONS READ THIS PAGE BEFORE PROCEEDING Rosemount Analytical designs manufactures and tests its products to meet many national and international standards Because these instruments are sophisticated technical products you must properly install use and maintain them to ensure they continue to operate within their normal specifications The following instructions must be adhered to and integrated into your safety program when installing using and maintaining Rosemount Analytical products Failure to follow the proper instructions may cause any one of the following situations to occur Loss of life personal injury property damage damage to this instrument and warranty invalidation Read all instructions prior to installing operating and servicing the product If this Instruction Manual is not the correct manual telephone 1 800 654 7768 and the requested manual will be provided Save this Instruction Manual for future reference If you do not understand any of the instructions contact your Rosemount representative for clarification Follow all warnings cautions and instructions marked on and supplied with the product Inform and educate your personnel in the proper installation operation and maintenance of
84. JUNCTION BOX TRANSMITTER FACTORY SET TO TRANSMITTER REFERENCE ELECTRODE IMPEDANCE JUMPERS JP 6 LOW IMPEDANCE JP 7 HIGH IMPEDANCE FACTORY SET 6 69862 ASSV JUMPER POSITIONS JP 1 RTD PT1000 k JP 2 RTD PT100 JP 3 RTD 3K BALCO FACTORY SET TO JP 2 O 0000000000000000 o INITIAL ANALOG PCB SETUP DWG NO TY OF COMPONENTS NOT SHOWN FOR CLARITY 40308110 FIGURE 2 2 Model 3081 pH ORP Transmitter Analog Board 9 MODEL 3081 pH ORP SECTION 2 0 INSTALLATION 6 There are more jumpers on the CPU board Refer to Figure 2 3 These jumpers are factory set and should NOT need to be moved This step is for trou bleshooting purposes only Verify that jumpers JP 1 JP 3 and JP 4 m di on the CPU board are in the positions pre SONDERN shown in Figure 2 3 For installations where 50 Hz ac power is present closing JP 3 may improve immunity of the trans 5e ec WRITE ENABLE CLOSED mitter to noise JP3 50 60 HZ POWER OPEN JP2 JP1 BLIND 2 is a o X o o 7 To reassemble the stack place the dis play board on the CPU board Be sure the display board is properly oriented The small window the infrared detector MAJORITY OF COMPONENTS NOT SHOWN FOR CLARITY for the remote controller marks the top of xo
85. L ON LINE ORDERING NOW AVAILABLE ON OUR WEB SITE CUSTOMER SUPPORT CENTER http www 1 800 854 8257 sy S000 32 Credit Cards for U S Purchases Only VISA cards d 2 2 QUA So 2 em E Emerson Process Management Rosemount Analytical Inc 2400 Barranca Parkway n Irvine CA 92606 USA gt Tel 949 757 8500 Fax 949 474 7250 7 http www raihome com E M E RSO N Rosemount Analytical Inc 2004 Process Management
86. MENTS 10 1 General 10 2 Entering and Leaving the Program Menu 10 3 Output Ranging 10 4 Diagnostic Parameters 10 5 Temperature Element 10 6 Display Units 10 7 Generating a Test Current 10 1 GENERAL This section describes how to do the following assign ORP values to the 4 and 20 mA outputs set the current generated by the transmitter during hold set the current generated by the transmitter when a fault is detected change sensor diagnostic limits change the units of the displayed variables program a security code 7 simulate output currents for testing Factory default settings are given in Table 10 1 If default settings are acceptable the transmitter is ready for cal ibration See Section 9 0 Calibration of ORP Measurements There is no way to automatically reset the transmit ter to factory defaults Settings must be returned to default values one at a time Figure 5 5 shows the menu tree 10 2 ENTERING AND LEAVING THE PROGRAM MENU Press PROG on the infrared remote controller IRC to enter the Program menu To save new settings press ENTER To leave the Program menu without saving new values press EXIT Pressing EXIT with a prompt showing returns the display to the first prompt in the sub menu Pressing EXIT again returns the transmitter to the process display If program settings are protected with a security code pressing PROG or CAL will cause the Id screen to appear Key in the security code and p
87. OMER MODEL 328A 08 HAS UNDRESSED COAXIAL CABLE CABLE MUST BE TERMINATED BEFORE WIRING SENSOR TO TRANS MITTER CENTRAL CONDUCTOR IS pH SIGNAL TB 10 AND SHIELD IS REFERENCE SIGNAL TB 7 SEE SENSOR INSTRUCTION SHEET FOR DETAILS AUTOMATIC TEMPERATURE COMPENSATION MUST BE TURNED OFF SEE SECTION 8 5 FIGURE 3 18 Wiring diagram for Model 328A 23 MODEL 3081 pH ORP SECTION 3 0 WIRING MODEL 3081pH ORP MODEL 3081 pH ORP TRANSMITTER TRANSMITTER SOL pH SOL pH GND GUARD GND GUARD p EXTENSION CABLE PN 661 646983 UNPREPPED RED CRAY BLUE WHITE WHITE BLACK WHITE RED EXTENS TON CABLE PN 9200273 CUNPREPPED OR PN 23646 01 PREPPED WHITE COAX WHITE GRAY INNER DRAIN 320HP 10 55 320HP 10 58 JUNCTION BOX JUNCTION BOX PN 22996 02 INCLUDES PREAMPLIFIER SEE NOTE 2 BOARD PN 23557 00 SENSOR WIRES pH ELECTRODE pH ELECTRODE CLEAR o SENSOR WIRES SHIELD CLEAR NOTES PLACE PREAMPLIFIER SELECTION SWITCH S1 IN TRANS NOTES POSITION SEE SECTION 2 2 1 PLACE PREAMPLIFIER SELECTION SWITCH S1 IN TERMINALS IN JUNCTION BOX ARE NOT NUMBERED SENSOR JUNCTION BOX POSITION SEE SECTION 2 2 COUNT POSITION FROM LEFT TO RIGHT AS SHOWN IN _ JUMPERS SUPPLIED BY CUSTOMER DRAWING CUSTOMER MUST INSTALL AND WIRE pH ELECTRODE AND TEM JUMPERS SUPPLIED BY CUSTOMER PERATURE SENSOR e WIRE pH ELEGTRODE SEE SENSOR MANUAL FOR
88. OPA 9 SI 1 81 STVNIN831l TVN9IS 5 ALILNA 1808 031412345 3SIMY3HLO 55321 S310N Z Z 133HS NO S310N 111 378V4 310N 335 A NO V38V 55970 NI 3SN 802 32 3831 1 6 310 535 Q30131HS S3HIM 318 2 G3GN3NADO238 OMY 22 YALLIWSNVYL 310W3H SLZ 13000 INDIOW3SOH 111 338v1 p 310N 335 v3uv 55772 NI 35 103 32VJ831NI 00 195 2 dWv3ug 6 310N IW 180 1195 310WN3H Siz 7300 1NhOW3SOH 305425 Het 111 21891 ONY 3LON 335 A NO 55 79 NI 350 305 3OVJH31NI U3SIIINSNVHI 310W3H 1806 SLZ 13004 1NnDW3SOH 6 310N 33S 50131 5 2 02 OL 9344349 10 9 9 2 Nd G3 3d38dND 52120025 Nd BOSN3S 37892 030N3AWO23H He 111 318 310N 335 ANO V38V 55772 NI 3SN 803 30V 383iNI dHO Hd 1805 T300W NSNVHI JLOWJY 522 13000 1NnOW3SOH V3uV 1 55772 NI 35 803 LENN 7051405 310W3H Q3UVHBdNI HOSN3S pue Grom e bip Ab adu on i pub 10212 buy S 34 gen TR 919551 T amp D 9190002 12 lt 09 3H3HM SNO1110NO2 ONIMOTIO4 3Hl 133W TIVHS SIYNIWYAL HOSN3S 01 03123 02 S321A30 H3H10 8 PhOZ ONY MusZ
89. OTE COMMUNICATIONS If your communicator does not recognize the Model 3081 pH ORP transmitter the device description library may need updating Call the manufacturer of your HART communication device for updates 15 3 ASSET MANAGEMENT SOLUTIONS Asset Management Solutions AMS is software that helps plant personnel better monitor the performance of analytical instruments pressure and temperature transmitters and control valves Continuous monitoring means maintenance per sonnel can anticipate equipment failures and plan preventative measures before costly breakdown maintenance is required AMS uses remote monitoring The operator sitting at a computer can view measurement data change program settings read diagnostic and warning messages and retrieve historical data from any HART compatible device including the Model 3081 pH ORP transmitter Although AMS allows access to the basic functions of any HART compatible device Rosemount Analytical has developed additional software for that allows access to all features of the Model 3081 pH ORP transmitter AMS can play a central role in plant quality assurance and quality control Using AMS Audit Trail plant operators can track calibration frequency and results as well as warnings and diagnostic messages The information is available to Audit Trail whether calibrations were done using the infrared remote controller the Model 275 HART communicator or AMS software AMS operates in Windows 95 See
90. P 17 MODEL 3081 pH ORP BNC BNC REFERENCE IN AND pH mV IN RED SENSE WHITE RTD IN REMOVE BNC AND TERMINATE COAXIAL CABLE BEFORE WIRING SENSOR TO TRANSMITTER SEE FIGURE 3 23 ALTERNATIVELY USE A BNC ADAPTER PN 9120531 OR ORDER MODEL OPTION 62 SENSOR WITH BNC REMOVED AND TER MINATIONS COMPATIBLE WITH 3081 pH ORP IF USING A BNC ADAPTER THE RED WIRE IS MV OR pH IN AND THE BLACK WIRE IS REFERENCE IN TO PREVENT SHORT CIRCUITS TO THE TRANSMITTER HOUSING INSULATE THE BNC WITH BY WRAPPING IT WITH ELECTRICAL TAPE FIGURE 3 2 Wire functions for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 before removing BNC and terminating cable CLEAR REFERENCE IN ORANGE pH mV IN RED RTD SENSE WHITE RTD IN IF USING A BNC ADAPTER THE RED WIRE IS OR pH IN AND THE BLACK WIRE IS REFERENCE IN TO PREVENT SHORT CIRCUITS TO THE TRANSMITTER HOUS ING INSULATE THE BNC WITH BY WRAPPING IT WITH ELECTRICAL TAPE FIGURE 3 3 Wire functions for Models 399 02 399 09 381pH 30 41 and 381pHE 31 41 after removing BNC and terminating cable Wire functions for Models 399 09 10 62 381pH 30 42 and 381pHE 31 42 as received MODEL 3081pH O0RP TRANSMITTER SQL pH GND GUARD RTD RTN SHIELD EARTH GND SENSOR CABLE NOTES 1 PLACE PREAMPLIFIER SELECTION SWITCH 51 IN TRANSMITTER POSITION SEE SECTION 2 2 2 IF SENSOR HAS 3K BALCO RTD SET JUMPER SECTION 2 2 AND PROGRAM TR
91. PUT CURRENT DISPLAY The transmitter generates a 4 to 20 mA output signal directly proportional to the ORP of the sample The output signal also appears on the temperature output display line The output signal can be displayed as current in mA or as percent of full scale SECURITY CODE The security code unlocks the transmitter and allows complete access to all menus The transmitter is shipped with security code disabled 10 6 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the dISPLAY sub menu appears Press ENTER The screen displays the tYPE prompt Press or to toggle between pH and OrP Press ENTER to save The screen displays the tEMP prompt Press or v to toggle between C and F Press ENTER to save The screen displays the OUtPUt prompt Press or to toggle between and CUr Press ENTER to save The screen displays the COdE prompt Use the editing keys to enter a security code between 001 and 999 Entering 000 disables the security feature Press ENTER to save Press EXIT to return to the process display 83 MODEL 3081 pH ORP SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 7 GENERATING A TEST CURRENT 10 7 1 Purpose This section describes how to generate output currents for testing recorders and data handling systems 10 7 2 What happens while the transmitter is generating a test current 1 The output current goes to the programmed test value and remains ther
92. REMIT 58 8 4 Diagnostic 5 60 8 5 Temperature Related 05 0 000040 00 10 aquqa kwa 64 8 6 Display UniS EE 66 8 7 Buffer Calibration 67 8 8 Isopotential Parameters pud 69 8 9 Generating Test Current u u uuu ceret 71 9 0 CALIBRATION ORP MEASUREMENTS 72 9 1 72 9 2 Entering and Leaving the Calibrate 72 9 3 Using the Hold 72 9 4 Temperature Calibration U nnne 73 9 5 Standardizati fis R uuu ET 74 10 0 PROGRAMMING FOR ORP MEASUREMENTS 75 WO Generale EUH 75 10 2 Entering and Leaving the Program Menu 75 10 3 saepe 77 10 4 Diagnostic 004 00400000000 uqu ana nnns en nnne en 79 10 5 Temperature cree tet nece ayam pcd 82 10 62 Display Unts scsi ELE 83 10 7 Generating a Test nnne sn nnne 84 110 MAINTENANCE
93. S WARRANTY NO OTHER WARRANTIES ARE GRANTED INCLUDING BUT NOT LIMITED TO EXPRESS AND IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE RETURN OF MATERIAL Material returned for repair whether in or out of warranty should be shipped prepaid to Rosemount Analytical Inc Uniloc Division 2400 Barranca Parkway Irvine CA 92606 The shipping container should be marked Return for Repair Model The returned material should be accompanied by a letter of transmittal which should include the following information make a copy of the Return of Materials Request found on the last page of the Manual and provide the following there on 1 Location type of service and length of time of service of the device 2 Description of the faulty operation of the device and the circumstances of the failure 3 Name and telephone number of the person to contact if there are questions about the returned material 4 Statement as to whether warranty or non warranty service is requested 5 Complete shipping instructions for return of the material Adherence to these procedures will expedite handling of the returned material and will prevent unnecessary additional charges for inspection and testing to determine the problem with the device If the material is returned for out of warranty repairs a purchase order for repairs should be enclosed The right people the right answers right now ROSEMOUNT ANALYTICA
94. SAFE amp EXPLOSION PROOF 41 Intrinsically Safe Installations 4 2 Explosion Proof Installations 41 INTRINSICALLY SAFE INSTALLATIONS The installation wiring operating parameters or agency tags for intrinsically safe operation are given in Figures 4 1 4 2 and 4 3 4 2 EXPLOSION PROOF INSTALLATIONS The installation wiring and operating parameters for explosion proof operation are given in Figure 4 4 This document contains informotion proprietary to Rosemount Anatytical and is not fo be made available to those who may compete with Rosemount Analytical RELEASE OATE Rey REVISIONS MIN 03 1807 6356 A eco DESCRIPTION DATE CHK 8 125 at 120 015 n ROSEMOUNT ANALYTICAL MODEL 3081 pHORP lE TS tTamb 40 C T4 Tomb 65 C K NO 9602494 SUPPLY max In 30 VDC 2 5603 015 I max in 200 mA 4XR 250 loo eeiirzs g W max in 0 9 W Ceq 0 uF Legs pH 2 180 005 SIGNAL INPUT t 13 44 t mox ou volts THIS DOCUMENT IS 2X FULL R i max out 170 mA W mox out 0 6 watts CERTIFIED BY Ceq 0 012uF Leq 0 pH BAR aA 1405 005 tm REV LL as REV 650 015 F REVISIONS NCT W O AGENCY APPROVIL w 1 3005 015 s 7 DIRECTION OF NATURAL GRAIN
95. TALLING AND WIRING A ROSEMOUNT ANALYTICAL SENSOR TO THE MODEL 3081 pH ORP TRANSMITTER Model number RTD 1 THE MODEL NUMBER OF THE SENSOR Look on the label Also note the model option string MODEL 396P PT 100 P N 396P 01 10 55 e Ifthe label is missing or unreadable see the flowcharts on pages 28 through 30 ROSEMOUNT ANALYTICAL Write the sensor model number here Model option string 2 THE TYPE OF TEMPERATURE ELEMENT Look on the label Sensor e If the label is missing or unreadable measure the resistance between the RTD leads Write the temperature element RTD here white measure If resistance is the RTDis resistance about 110 ohms Exceptions about 3000 ohms Balco 3K are black and white 2 328A has no RTD 3 320HP has separate distinctive RTD 3 THE LOCATION OF THE PREAMPLIFIER INSIDE OR OUTSIDE THE TRANSMITTER e If the sensor is wired through a junction box the preamplifier is ALWAYS in the junction box or the sensor preamplifier sensor mounted junction box transmitter sensor junction junction box box preamplifier transmitter transmitter preamplifier sensor fthe sensor is wired directly to the transmitter the preamplifier can be in either the sensor or the transmitter preamplifier transmitter transmitter preamplifier sensor sensor Look at the wir
96. TURE COMPENSATION The impedance of the glass electrode changes with tem perature For changes in glass impedance to be a useful indicator of electrode condition the measurement must be corrected to a reference temperature WARNING AND FAILURE LIMITS FOR THE GLASS ELECTRODE Warning tells the user that the glass electrode impedance is approaching the failure limit Low and high warning and failure limits are programmable Low imped ance means the glass electrode has cracked and is no longer functioning High impedance often means the elec trode is aging and may soon need replacement High glass impedance may also mean the electrode is not immersed in the liquid stream Figure 8 1 shows suggested settings for glass impedance warning and failure limits 10000 High impedance fault 1500 megohms 1000 High impedance warning 1000 megohms Glass impedance megohms lt Low impedance warning 20 megohms 10 3 Low impedance fault 10 megohms FIGURE 8 1 Suggested Glass Impedance Warning and Failure Limits Typical glass impedance is about 100 megohms at 25 C A broken electrode has an impedance of 10 megohms or less A glass impedance greater than 1000 megohms suggests the electrode is nearing the end of its service life High imped ance may also mean the electrode is not immersed in the process liquid 60 MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 4 REFERENCE IMPEDANCE The majori ty of reference electrodes used
97. Temperature Correction IMPtC On Off On Glass Electrode High Impedance Fault GFH 0 to 2000 megohms 1500 megohms 2 3 4 5 Glass Electrode High Impedance Warning GWH 0 to 2000 megohms 1000 megohms 6 Glass Electrode Low Impedance Warning GWL 0 to 900 megohms 20 megohms 7 Glass Electrode Low Impedance Fault GFL 0 to 900 megohms 10 megohms 8 Glass Impedance Calibration Warning CAL 0 to 500 0 not Active 9 Reference Cell Impedance Type rEF LO HI LO 10 Reference Cell High Impedance Fault rFH 0 to 2000 megohms HI 1500 megohms 0 to 2000 kilohms LO 140 kilohms 11 Reference Cell High Impedance Warning rWH 0 to 2000 megohms HI 1000 megohms 0 to 2000 kilohms LO 40 kilohms 12 Reference Cell Low Impedance Warning rWL 0 900 megohms 20 megohms Does not apply for low impedance reference cell 13 Reference Cell Low Impedance Fault rFL 0 to 900 megohms 10 megohms Does not apply for low impedance reference cell C Temperature Section 8 5 tEMP 1 Auto Temperature Compensation tAUtO On Off On 2 Manual Temperature tMAn 15 to 130 C 25 C 5 to 266 F Temperature Sensor Type tC 100 3 100 4 1000 3 100 3 1000 4 3000 Display Section 8 6 dISPLAY Measurement type tYPE pH ORP pH Temperature Units tEMP C F C Output Units OUtPUt mA of full scale mA Code COdE 0 to 999 000 Buffer Section 8 7 bUFFEr Auto Calibration Function b AUtO ON OFF ON Buffers Selection List bUFFEr See Tables 8 2 and 8 3 Stan
98. UD2 ONY A YO SOA 39Vl1 0A 3Hi 9319359 10 008 og 01 1vn03 LSAN SALvuVddY FAVS ATIVOISNIQLNI 3H 40 XOUI SSI SPA find XOU SOAL HU 111 13 M INI INI 13004 1N3HHD2 XDUA 39V1710A SINZA3HIDD3H ONIAOT Od JHL LIJN 17 5 83188V8 412495 SnivHvddV 031 19055 522 73006 ONY 32VJH31NI B3LLINSNVHi 10 SH3l3WVHVd ALTING H3LLIWSNVHL JYI dNO Hd 1806 TOON Shivuvddv 339 A TIVOISNISINI _ 30 48 808 310W3H 00 90982 I A XOU 13000 BdAL JHL 5 ISDW 3505071943 INVISIS3H H3HIV3M V 1 2819 5 xouri ent ON 13004 H3Idl dWVdBd TVHO31NI H3IiINWSNYHI dHO Hd 180 3008 JHL 36 9t 5 6 5 5 Qv3isNI 03217111 38 00 19582 50 00 97582 43131 Su3isWVuvd ALIIN3 1806 504 VdJSN iSNV 23N ONY 9872448 VSI ISNV 111 37871 SINGW3HIfID3H OL WHOANOD LSMW 011 17 15 1 SHEL I OP 51104 OGZ SUJ SITOA 052 ONIO330X3 TVIIN3iDd 30 328005 V SNOIIIGNO2 TVWHONGV ND IWWYON uU3OND NIVINDO 30 03114405 38 LON LSNA Snivuvddv v3sv 3375 Q3131293dSNn PhOZ WUSZ Vi O AZ i NVHl SHOW 38015 HON 31VUdNd9 LON NYJ OL VddN ISNV 23N JHL ONY 9 ZidH VSI ISNV Q3NI 330 Sv SnivuvddV 3148415 3
99. VICE INFORMATION 1 2 3 4 5 DIAGNOSTICS wen m m amp 2 3 l i i 4 5 I 6 LOCAL DISPLAY i I 1 i i i 1 1 5 REVIEW SENSORS OUTPUTS DIAGNOSTICS DEVICE INFORMATION LOCAL DISPLAY 1 When Ref unit Mohms 2 When Ref unit kohms TEMPERATURE PV LRV PV URV pH PV rnge xfer Fun ANALOG OUTPUT HART OUTPUT Tag Descriptor Message Snsr text Date Diagnostics GFH GFL Ref unit RFH RFL GWL RwL 0 limit Cal warn xmtr 10 AD LOI units SECTION 6 0 OPERATION WITH MODEL 275 PV is Autocal SST SSS comp Oper iso 5nsr iso TC Temp comp Man temp Temp snsr ANALOG DUTPUT 1 PV AD 2 PV AO Damp 3 PV Hold 4 PV Fault Loop test Trim analog output Poll addr Temp unit Ref unit PV is Burst option Burst mode Num resp preams 2 Diagnostics GFH GFL Ref unit RFH limit Cal warn FIGURE 6 2b pH Menu Tree HART MODEL 3081 pH ORP SECTION 6 0 OPERATION WITH MODEL 275 PROCESS VARIABLES 1
100. Verify the interconnecting wiring point to point Fix or replace bad cable If cable is good replace the pH sensor 99 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 4 10 SLOPE Err HI SLOPE Err HI means that a two point buffer calibration attempt has failed The slope is too high gt 62 mV pH for a good measurement Troubleshooting Flowchart SLOPE Err HI A Repeat the calibration 1 Inaccurate buffers can cause a low slope Repeat the calibration using fresh buffers Alkaline buffers pH 10 or greater are particularly susceptible to changing value in air or with age If a high pH buffer was used in the failed calibration try a lower pH buffer when repeating the calibration For example use pH 4 and 7 buffer instead of pH 7 and 10 buffer 2 Allow adequate time for readings in buffer to become constant If the sensor was in a process substantially colder or hotter than the buffer allow at least 20 minutes for readings in the buffer to stabilize Alternatively place the sensor in a container of water at ambient temperature for 20 minutes before starting the calibration 3 Be sure the correct buffer values are being entered during calibration To minimize errors caused by entering the wrong buffer values use auto calibration procedure described in Section 7 5 4 Verify that the temperature reading is accurate Compare the sensor reading against a thermometer known to be accurate Recalibrate if necessary See the procedure in S
101. able Wiring Diagram for Models 397 54 62 396 54 62 and 389 02 54 62 as received Wiring Through a Remote Junction Box to the Transmitter 19 3 10 Wire Functions for Models 396R 50 396R 54 396R 54 61 396P 02 50 396P 02 54 396P 02 55 3854 04 and 381 41 52 20 3 11 Wiring Diagram for Models 396R 50 396R 54 396R 54 61 396P 02 50 396P 02 54 396P 02 55 3854 04 and 3814 41 52 Wiring Directly to the Transmitter 20 3 12 Wiring Diagram for Models 396R 50 396R 54 396R 54 61 396 02 50 396P 02 54 396P 02 55 3854 04 and 3814 41 52 Wiring Through a Sensor Mounted Junction to the Transmitter 20 3 13 Wire Functions for Models 396P 01 55 3854 03 3814 40 55 and 3814 43 55 21 3 14 Wiring Diagram for Models 396P 01 55 3854 03 381 40 55 and 381 43 55 21 3 15 Wire Functions for Model 385 02 400 22 3 16 Wiring Diagram for Model 385 02 L 22 3 17 Wire Functions for Model 328A 07 23 3 18 Wiring Diagram for Model 328 23 3 19 Wiring Diagram for Model 320 10 55 20000000 0 24 3 20 Wiring Diagram for Model 320 10 58 24 3 21 Wire Functions for Model 399 33 25
102. an one warning or fault message has been generated the messages appear alternately See Section 12 0 Troubleshooting for the meanings of the fault and warning messages CALIBRATE PROGRAM Std tEMP ADj 10 VEr 81PH 01 ShoW FLt Std 1000 tEMP OutPut dIAGnOStIC tEMP dISPLAY 4 MA 1400 rOFFSt 060 tC 100 3 tYPE ORP tESt 12 00 I 20 1400 OFF tEMP C I I HoLd 21 00 IMPtC OFF OUtPUt CUr I I FAULt 22 00 rEF LO COdE 000 I dPn 0 00 140 rWH 040 rWL 000 I TFL 000 PROMPT Diag Message FIGURE 5 5 Menu Tree for ORP MODEL 3081 pH ORP SECTION 5 0 OPERATION WITH REMOTE CONTROLLER 5 7 SECURITY 5 7 1 General Use the programmable security code to protect program and calibration settings from accidentally being changed The transmitter is shipped with the security fea ture disabled To program a security code refer to Section 8 6 Display Units PROGRAM 5 7 2 Entering the Security Code Id 500 1 If calibration and program settings are protected with a security code pressing PROG EXIT ENTER or CAL on the infrared remote controller causes the Id screen to appear Use the editing keys to enter the security code Press ENTER If the security code is correct the first sub menu app
103. and temperature are stable or at worst slowly drifting Take a grab sample from the process stream or sample line at a point as close as possible to the pH sensor Note the transmitter reading PHirans at the time the sample was taken Measure the pH of the sample using the second pH meter For best results make the measurement at the same temperature as the process Note the current process reading Calculate the corrected reading from the equa tion pHcorr pHcurr pHsiq PHtrans where pHeorr is the corrected pH value pHcurr is the current process reading is the pH measured using the standard instrument and PHirans is the pH measured by the trans mitter when the sample was taken Use the editing keys to change the flashing display to calculated above Press ENTER to save the corrected pH The transmitter converts the difference between pHcorr and pHcurr into mV and com pares the result with the value programmed for rOFFSt in Section 8 4 Diagnostic Parameters If the difference exceeds the value for rOFFSt the transmitter will not accept the data and will not update the display to the corrected pH The message StD Err will appear If the corrected pH value is acceptable the display will change to look like the screen at the left The slope displayed is the current electrode slope If the slope is incorrect and the correct value is known use the editing keys to change the slope to the desired value
104. ans that jumper JP1 on the CPU board is not in place If the jumper is not in place the transmitter cannot be programmed or calibrated Troubleshooting WritE Err Refer to Section 2 2 Check the position of jumper JP1 on the CPU board If the jumper is hanging off one of the pins place it across both pins If the jumper is missing entirely use jumper JP3 50 60 Hz which is not a critical jumper THERE ARE SIMILAR NUMBERED JUMPERS ON THE ANALOG BOARD THE JUMPER TO BE CHECKED IS ON THE CPU BOARD WHICH IS THE CENTER BOARD IN THE STACK Turn the power to the transmitter off and then back on Toggling the power should cause the message to disappear If the message does not disappear replace the electronic board stack PN 23574 02 101 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 4 15 FACt FAIL FACt FAIL appears if the transmitter factory calibration message has been triggered A stray noise spike can cause this message to appear If the pH reading seems acceptable reset the calibration flag 1 Enter the factory calibration menu by pressing on the IRC ten times The display will not change Immediately press FActorYCAL appears in the display Press NEXT rEPAir appears in the display Press NEXT ConFiG appears in the display Press NEXT rESEt appears in the display Press ENTER rESEtCFG appears in the display Press ENTER rESEt appears again Press NEXT FActorYCAL reappears o Press ENTER
105. asurement is only as good as the calibration and the calibration is only as good as the buffers A careful buffer calibration is the first step in making an accurate pH measurement Calibrate with buffers having pH values that bracket the pH of the process For example if the pH is between 8 and 9 calibrate with pH 7 and 10 buffers Commercial buffers having interme diate range pH are readily available Buffers outside the range pH 3 0 to pH 10 0 may not be readily available and must be prepared by the user Allow time for the sensor and buffers to reach the same temperature If the process temperature is more than 10 C different from the buffer allow at least 20 minutes For best results calibrate with buffers having the same temperature as the process If the buffer and process temperature differ by more than about 15 C an error as great as 0 1pH may result Be careful using buffers at high temperatures Protect the solution from evaporation Evaporation changes the concentration of the buffer and its pH Be sure the pH of the buffer is defined at high temperatures The pH of many buffers is undefined above 60 C Finally no matter what the tem perature is allow the entire measurement cell sensor and solution to reach constant tempera ture before calibrating The pH of a buffer changes with temperature Equations relating pH to temperature for common buffers have been programmed into the Model 3081 pH transmitter During auto calibrat
106. at the measurement temperature to the pH at a reference temperature by entering a solution temperature coefficient change the transmitter isopotential pH NOTE Do NOT change the isopotential pH of the transmitter unless you are thoroughly familiar with the role of sensor and transmitter isopotential points in pH measure ment OR unless the sensor operating instructions specifically state that the isopotential pH is a value other than pH 7 8 8 2 Definitions 1 pH AT A REFERENCE TEMPERATURE Certain industries for example power generation use pH to indirectly measure the concentration of dilute alkaline solutions typically ammonia The pH of dilute ammonia solutions is a strong function of temperature Therefore to make pH solely a measure of concentration the pH must be converted to a value at a reference tem perature The correction factor is expressed as the pH change per unit temperature change in C The correction is commonly called the solution temperature coefficient The almost uni versal reference temperature is 25 C Example The temperature coefficient of dilute aqueous ammonia solutions 0 1 to 5 ppm is about 0 032 the minus sign means the pH decreases as temperature increases If the pH at 31 C is 8 96 the pH at 25 C is 8 96 0 032 25 31 9 15 ISOPOTENTIAL pH The isopotential pH is the pH at which the cell voltage is independent of temperature The closer the agreement between the transmi
107. ated sources at 24 Vdc and 200 mA each A junction box PN 2002188 allows as many as nine 3081 pH ORP transmitters to be powered from each output For more information refer to product data sheet 71 515 1 2 2 Alarm Module The Model 230A Alarm Module receives the 4 20 mA signal from the Model 3081 pH ORP transmitter and activates two alarm relays Specify alarm configuration at the time of ordering High high low low and high low are available Dead band is adjustable as high as 15 of full scale For more information refer to product data sheet 71 230 1 2 3 Model 275 HART amp COMMUNICATOR The Model 3081 pH ORP transmitter is compatible with the Model 275 HART communicator The HART Communicator allows the user to view pH or ORP temperature and current output The user can also program and configure the transmitter and can download data for transfer to another transmitter or computer The Model 275 commu nicator attaches to any wiring terminal across the output loop A 250 ohm load must be between the power supply and the transmitter Order the Model 275 communicator from Rosemount Measurement Call 800 999 9307 Year 2000 Compliance Millennium Status Rosemount Analytical Uniloc Division certifies that all instruments designed and manufactured by the Uniloc Division do not have calendars No instruments manu factured by Uniloc Division keep track of days months or years This has been validated by reviewing all test a
108. ation Regular buffer calibrations are still needed to update the sensor slope value For best results take the grab sample from a point as close as possible to the pH sensor and measure the sample at the same temperature as the process A Aim the infrared remote controller IRC at the LCD display Press HOLD on the IRC HoLd OFF will appear Press v to toggle the display to HoLd On Press ENTER to engage the hold mode The HOLD indicator will appear to the left of the pH value B Press CAL CALIbrAtE will appear Press NEXT Std will appear Press ENTER The measured value will appear C Take a grab sample of the process and measure it with your reference instrument Use the editing keys to adjust the value on the Model 3081pH ORP to match the reference instrument Press ENTER to save the corrected pH value If the value is acceptable the sensor slope is displayed The slope has not been changed Press RESET to return to the process display F After calibration press HOLD HoLd On will display Press to toggle the display to HoLd Off Press ENTER to save this into memory The HOLD indicator on the display will turn off HART Communicator Fast Key Sequences Buffer Calibration Toggle Hold Mode View pH value Standardize pH Upper Range Value View Analog Output Trim Analog Output pH Lower Range Value View Transmitter Status CALIBRATE PROGRAM CALIbrAtE Std tEMP AdJ CAL bF1 Std 7 00 tEMP 25 0 InPut 58 9 10
109. ault value The allowed ranges are Type of reference electrode Allowed range Low impedance LO in step 6 not applicable High impedance in step 6 0 900 megohms Entering 0000 disables the feature When the reference electrode impedance goes below the fault value the transmitter displays the diagnostic message rEFFAIL and sets a fault condition Press ENTER to save The prompt appears but is disabled when LO is selected in step 6 11 Press EXIT to return to the process display 81 MODEL 3081 pH ORP 82 SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 5 TEMPERATURE ELEMENT 10 5 1 Purpose This section describes how to match the transmitter to the type of temperature element in the ORP sensor 10 5 2 Definition TEMPERATURE ELEMENT ORP sensors use a variety of temperature ele ments The Model 3081 ORP transmitter recognizes the following temperature elements and configurations a three and four wire 100 ohm platinum RTDs b three and four wire 1000 ohm platinum RTDs c 3000 ohm Balco RTD A 100 ohm platinum RTD has a resistance of 100 ohms at 0 C A 1000 ohm plat inum RTD has a resistance of 1000 ohms at 0 C A 3000 ohm Balco RTD Balco is an alloy of 70 nickel and 30 iron has a resistance of 3000 ohms at 25 C Although only two lead wires are necessary to connect the RTD to the transmit ter connecting a third and sometimes fourth wire allows the transmitter to cor rect for the resistance of the
110. be free from defects in workmanship and material under normal use and service for a period of ninety 90 days from date of shipment by Seller Goods part s and consumables proven by Seller to be defective in workmanship and or material shall be replaced or repaired free of charge F O B Seller s factory provided that the goods parts s or consumables are returned to Seller s designated factory transportation charges prepaid within the twelve 12 month period of warranty in the case of goods and part s and in the case of consumables within the ninety 90 day period of warranty This warranty shall be in effect for replacement or repaired goods part s and consumables for the remaining portion of the period of the twelve 12 month warranty in the case of goods and part s and the remaining portion of the ninety 90 day warranty in the case of consumables A defect in goods part s and consumables of the commercial unit shall not operate to condemn such com mercial unit when such goods parts s or consumables are capable of being renewed repaired or replaced The Seller shall not be liable to the Buyer or to any other person for the loss or damage directly or indirectly arising from the use of the equipment or goods from breach of any warranty or from any other cause All other warranties expressed or implied are hereby excluded IN CONSIDERATION OF THE STATED PURCHASE PRICE OF THE GOODS SELLER GRANTS ONLY THE ABOVE STATED EXPRES
111. ble and reinstall it in the conduit 3 To avoid induced noise in the sensor cable run it as far away as possible from power cables relays and electric motors Keep sensor wiring out of crowded panels and cable trays 105 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 4 Occasionally noise can travel into the transmitter housing from the metal it is mounted on The noise is then radiated into the transmitter electronics If isolating the transmitter from its metal mounting eliminates the symptoms move the transmitter to a different location or mount it with isolating materials 5 If ground loop problems persist consult the factory A visit from an experienced service technician may be required to solve plant induced problems 12 5 9 Temperature Reading Is Inaccurate A Totroubleshoot temperature problems refer to Section 12 4 6 B To calibrate the temperature response of the sensor refer to Section 7 4 C If necessary automatic temperature compensation can be temporarily disabled and the transmitter placed in manual temperature compensation Refer to Section 8 5 For manual temperature choose a temperature equal to the average temperature of the process The resulting pH reading will be in error The more variable the temperature and the further from pH 7 the greater the error 12 5 10 HART Communications Problems A Ifthe Model 275 Communicator software does not recognize the Model 3081pH ORP transmitter order an upgrade fr
112. bleshooting approach offered in Section 12 6 to diagnose and correct less common or more complex problems 12 4 TROUBLESHOOTING WHEN A DIAGNOSTIC MESSAGE IS SHOWING The Model 3081 pH ORP transmitter continuously monitors the measurement loop sensor and transmitter for problems If a problem is detected the transmitter displays a fault or error message The message appears in the temperature out put area of the main display The table lists each diagnostic message and the section to consult for help MESSAGE SECTION GLASSFAIL GLASSWArn rEF FAIL rEF WArn CALIbrAtE tEMP HI tEMPLO LInE FAIL InPUt WArn SLOPE Err LO SLOPE Err HI Std Err rOM FAIL CPU FAIL AdC WArn CyCLE PWr WrltE Err FACt FAIL 90 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 4 1 GLASSFAIL GLASSFAIL is an electrode fault message It means the glass impedance is outside the programmed Glass Fault High GFH or Glass Fault Low GFL limit Glass Fault High suggests the electrode is aging or the electrode is not immersed in the process liquid Glass Fault Low implies the pH sensitive glass is cracked GLASSFAIL also appears if inappropri ate limits have been entered into the transmitter If the measurement system was previously commissioned and operating correctly GLASSFAIL likely means a real prob lem exists However if the system is being started up or if the advanced diagnostic feature is being used f
113. ce for temperature is recommended A third setting SPC appears in addition to On and OFF Do not select SPC the setting is intended for factory use Press ENTER to save The GFH prompt appears Use the editing keys to change the display to the desired glass electrode impedance high fault value The allowed values are between 0 and 2000 megohms Entering 0000 disables the feature When the glass electrode imped ance exceeds the fault value the transmitter displays the diagnostic message GLASS FAIL and sets a fault condition Press ENTER to save GWH prompt appears In the transmitter display UJ is W Use the editing keys to change the display to the desired glass electrode impedance high warning value The allowed values are between 0 and 2000 megohms Entering 0000 disables the feature When the glass electrode impedance exceeds the warning value the transmitter dis plays the diagnostic message GLASSWArn Press ENTER to save The GWL prompt appears Use the editing keys to change the display to the desired glass electrode impedance low warning value The allowed values are between 0 and 900 megohms Entering 0000 disables the feature When the glass electrode imped ance drops below the warning value the transmitter displays the diagnostic message GLASSWArn Press ENTER to save The GFL prompt appears Use the editing keys to change the display to the desired glass electrode impedance low fault value The allowed values are bet
114. ce is outside the programmed Glass Warning High GWH or Glass Warning Low GWL limit Ideally when the measurement system exceeds the glass warning limits the user will have adequate time to diagnose and correct problems before a failure occurs High impedance implies the electrode is aging or the sensor is not completely submerged in the process liquid Low impedance suggests the pH sen sitive glass is cracked The message also appears if inappropriate limits have been entered into the transmitter If the measurement system was previously commissioned and operating correctly GLASSWArn likely means a real prob lem exists However if the system is being started up or if the advanced diagnostic feature is being used for the first time GLASSWArn could be caused by a miswired sensor or by programmed limits that are not correct for the sensor NOTE GLASSWArn is a sensor diagnostic message All sensor diagnostic messages are optional They can be turned off To disable sensor diag nostic messages refer to Section 8 4 3 Troubleshooting Flowchart GLASSWArn Troubleshooting GLASSWArn problems is exactly the same steps as troubleshooting GLASSFAIL problems Refer to Section 12 4 1 12 4 3 rEF FAIL rEF FAIL is an electrode fault message rEF FAIL means that the reference impedance exceeds the programmed Reference Fault High RFH limit A plugged or dry reference junction is the usual cause of a high reference impedance High reference impeda
115. ches the nominal pH buffer value i e 4 01 Press ENTER to save the first calibration point CAL bF2 will appear D Remove the sensor from the first buffer rinse and place in the second buffer Press ENTER bF2 will flash until the reading is stable Press or V until the small number next to bF 2 matches the nominal pH buffer value i e 10 00 pH Press ENTER to save the second calibration point E The calibration is complete but the transmitter remains in the CALIbrAtE sub menu for two minutes after ENTER is pressed Press RESET to return to the process display immediately F Place sensor in the process G Optional For maintenance purposes track the slope of the pH electrode The slope value of a new electrode is 59mV per pH unit and this value falls over time The sensor should be changed when the slope nears 47 5mV per pH To view the slope value use the following steps Press CAL CALIbrAtE will appear Press NEXT Std will appear Press ENTER The current pH value will appear next to Std Press ENTER SLOPE and the current slope value will appear Record this number as the slope value Press RESET to return to the process display H After calibration press HOLD HoLd On will display Press to toggle the display to HoLd Off Press ENTER to save this into memory The HOLD indicator on the display will turn off Standardizing to Match a Reference Instrument Note Standardization does not perform a true calibr
116. d C Reference lead Suspect Good sensor sensor Buffer or solution FIGURE 11 2 Checking the Potential of the Reference Electrode Refer to the wiring diagram s for the sensors to identify the reference leads A laboratory silver silver chloride reference electrode can be used in place of the second sensor All Rosemount Analytical pH sensors have a silver silver chloride reference and most sensors use gelled saturated potassium chlo ride for the fill The potentials of a good sensor reference electrode and a saturated silver silver chloride laboratory electrode will agree within about 20 mV 11 3 4 Rejuvenating Reference Electrodes Occasionally a poisoned or plugged reference electrode can be reconditioned Although the electrode seldom recovers completely the procedure might extend the life of the sensor by a few weeks a Clean the sensor as thoroughly as possible b Soak the sensor for several hours in a hot NOT BOILING 3 potassium chloride solution Prepare the solution by dissolving 3 g of potassium chloride in 100 mL of water c Soak the sensor in pH 4 buffer at room temperature overnight d Calibrate the sensor in buffers and retest it in the process liquid 87 MODEL 3081 pH ORP SECTION 11 0 MAINTENANCE 11 4 ORP SENSOR MAINTENANCE 11 4 1 Frequency of Cleaning The frequency at which an ORP sensor should be inspected and cleaned can be determined only by experience If the process liquid coa
117. d if it is later necessary to return the transmitter to the fac tory 2 2 PRE INSTALLATION SETUP 2 2 1 Transmitter Default Settings Two jumpers and a switch may need to be changed from the factory default settings before installing the transmitter The settings tell the transmitter the type of temperature element in the sensor whether the reference electrode is high or low impedance and the location of the preamplifier The factory default settings are given below default setting temperature element Pt 100 RTD reference impedance low preamplifier location in transmitter If your sensor or system is different the transmitter settings must be changed If you do not know the type of temperature element in the sensor whether the reference electrode impedance is high or low or the location of the preamplifier refer to Sections 2 2 2 2 2 3 and 2 2 4 2 2 2 Temperature Element The Model 3081 pH ORP transmitter is compatible with sensors having Pt 100 Pt 1000 or 3K Balco RTDs pH and ORP sensors manufactured by Rosemount Analytical contain either a Pt 100 or a 3K Balco RTD Sensors from other manufac turers may have a Pt 1000 RTD For Rosemount Analytical sensors the type of temperature element in the sensor is print ed on the metalized tag attached to the sensor cable If the label is missing or unreadable determine the type of RTD by measuring the resistance across the RTD IN and RTD RTN leads For the majority of sensors manu
118. dard Auto Buffer Stabilization Time tIME 0 to 30 seconds 10 seconds Auto Stabilization pH Change PH 002 to 5pH 02 pH Isopotential Section 8 8 ISOPOtntAL Temperature Coefficient tCOEF 0 044 to 0 028 pH C 0 000 pH C Solution Isopotential pH ISO 1 35 to 20 12 pH 7 00 pH Sensor Isopotential pH Snr 0 00 to 14 00 pH 7 00 pH G Output Simulation Section 8 9 SIMOUtPUt Test tESt 3 80 to 22 mA 12 00 mA QON Tm 57 MODEL 3081 pH ORP IMPORTANT 58 SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 3 OUTPUT RANGING 8 3 1 Purpose This section describes how to do the following 1 2 3 4 assign pH values to the 4 and 20 mA outputs set the output current generated by the transmitter during hold set the output current generated by the transmitter when a fault is detected control the amount of dampening on the output signal 8 3 2 Definitions 1 CURRENT OUTPUTS The transmitter provides a continuous 4 20 mA output directly pro portional to the measured pH Any pH value between 0 and 14 can be assigned to the low out put 4 mA and the high output 20 mA HOLD During calibration and maintenance the transmitter output may be outside the normal operating range Placing the transmitter on hold prevents false alarms or the unwanted oper ation of chemical dosing pumps The transmitter output can be programmed to remain at the last value or to generate any current between 3 80 and 22
119. dardization against a reference thermometer Prompts guide the user through the calibration procedures 7 2 ENTERING AND LEAVING THE CALIBRATE MENU Press CAL on the infrared remote controller IRC to enter the Calibrate menu To store new settings in memory press ENTER To leave the Calibrate menu without storing new values press EXIT Pressing EXIT with a prompt showing returns the display to the first prompt in the sub menu Pressing EXIT a second time returns the transmitter to the process display If program settings are protected with a security code pressing PROG or CAL will cause the Id screen to appear Key in the security code and press ENTER The first sub menu will appear For more information see Section 5 7 Security A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing set tings use a different security code for each nearby transmitter See Section 5 7 Security and Section 8 6 Display Units for details 7 3 USING THE HOLD FUNCTION During calibration the sensor may be exposed to solutions having pH outside the normal range of the process To prevent false alarms and possible undesired operation of chemical dosing pumps place the transmitter in hold during calibration Activating hold keeps the transmitter output at the last value or sends the output to a previously determined value See Section 8 3 Output Ranging for details IMPORTANT After calibrati
120. de concentration is 100 ppm The table shows how slight changes in pH influence the ORP pH changes from 8 0 to 7 8 from 8 0 to 7 6 from 8 0 to 8 2 from 8 0 to 8 4 ORP changes by Around pH 8 and 1 00 ppm chlorine a change in ORP of 1 4 mV corresponds to a change in chlorine level of about 0 1 ppm Therefore if pH changed only 0 2 units and the true chlorine level remained constant at 1 00 ppm the apparent chlorine level determined by ORP would change about 0 3 ppm 14 8 CALIBRATION Although there is no internationally recognized ORP calibration standard the iron Il iron couple enjoys some popularity The standard is a solution of 0 1 M iron 1 ammonium sulfate and 0 1 M iron III ammonium sulfate in 1 M sulfuric acid The solution has good resistance to air oxidation If stored in a tight ly closed container the shelf life is one year Because the standard contains equal amounts of iron 1 and iron 111 the ORP does not change appreciably if the solution becomes slightly diluted In addition minor variability in actual concentration does not affect the standard ORP MODEL 3081 pH ORP The ORP of the iron Il iron standard when meas ured with a platinum electrode against a saturated sil ver silver chloride reference is 476 20 mV at 25 The range of values is caused primarily by the high and variable liquid junction potential generated in solutions containing high acid concentrations
121. e and four wire Pt 100 Pt 1000 and 3K Balco RTDs SOLUTION TEMPERATURE COMPENSATION The Model 3081 pH transmitter features solution temperature compensation The transmitter calculates and displays the pH at 25 C from the pH measured at any tempera ture The temperature coefficient of the liquid being measured must be known SENSOR DIAGNOSTICS Continuous diagnostics alert the user to impending or existing sensor failure Diagnostic messages in plain language aid in trou bleshooting The manual contains a thorough step by step troubleshooting guide HOUSING The Model 3081 pH ORP transmitter hous ing meets NEMA 4X standards The transmitter tolerates outdoor and harsh plant environments The housing also meets NEMA 7B explosion proof standards HAZARDOUS AREA INSTALLATION Circuits in the Model 3081 pH ORP transmitter are designed and built to be intrinsically safe when used with the appropriate safety barrier OUTPUT The 4 to 20 mA output signal is fully adjustable between 0 and 14 pH and between 1400 and 1400 mV During hold and fault conditions the out put can be programmed to remain at the last value or go to any value between 3 8 and 22 mA SECTION 1 0 DESCRIPTION AND SPECIFICATIONS 1 2 ACCESSORIES 1 2 1 Power Supply Use the Model 515 Power Supply to provide the dc loop power required by the Model 3081 pH ORP transmitter The Model 515 provides either a single source of power at 48 Vdc and 200 mA or two iso l
122. e and the consequences of an out of limits condition has a major influence on calibration frequency The narrower the control range and the greater the sensitivity of the process to control excursions the more often the sensor should be checked Finally if monitoring data are reported to regulatory agencies the agency itself may dictate the calibration frequency Use the following procedure to determine how often a pH sensor should be calibrated 1 Calibrate the sensor Record the date of calibration and the sensor response in buffers That is after calibrating place the sensor back in the buffers and record the pH and temperature reading in each buffer Also note the value of the reference offset and slope 2 Install the sensor in the process stream 3 After the appropriate period two weeks for a clean process several days for a dirty or aggressive process remove the sensor and check its performance in buffers Record the pH and temperature readings The performance of the sensor in buffer after it has been in service is called the as found condition Keeping a good record of as found data is an important step in determining the calibration frequency 4 lf the as found data are acceptable do not recalibrate the sensor Return it to the process Continue checking the cal ibration at the same interval 5 the as found data are not acceptable recalibrate the sensor After calibration check the sensor response in each buffer and record
123. e calibrated replace the sensor If the sensor has separate measuring and reference electrodes replace only the reference electrode 100 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING Lir the sensor is not rebuildable Try the reference electrode rejuvenation procedure described in Section 11 3 4 E the rejuvenated sensor can be calibrated the problem has been corrected If the sensor cannot be calibrated replace the sensor 12 4 12 rOM FAIL or CPU FAIL rOM FAIL or CPU FAIL means the transmitter electronics have failed Replace the electronic board stack PN 23574 02 12 4 13 AdC WArn or CyCLE PWr The AdC WArn or CyCLE PWr message appears momentarily when the transmitter has recognized an internal calcula tion problem The transmitter repeats the calculation and the message disappears once the calculation is successful If the message is displayed constantly the transmitter electronics may be faulty Troubleshooting AdC WArn or CyCLE PWr A Check transmitter performance by simulating pH inputs See Section 12 8 If the transmitter performs satisfactorily go to step B If the transmitter does not respond to simulated inputs replace the board stack PN 23574 02 B Ifthe transmitter responds to simulated inputs the problem must lie with the sensor or the interconnecting wiring Verify the interconnecting wiring point to point Fix or replace bad cable If cable is good replace the pH sensor 12 4 14 WritE Err WritE Err me
124. e out of the junction causing the liquid junction potential and the pH reading to drift It may take hours or days for the reading to stabilize For a discussion of the influence of ion mobility on liquid junction potentials see Section 13 4 Consult the sensor instruction manual for additional information Always recalibrate the sensor after cleaning If the sensor was cleaned with detergent or acid soak the sensor in pH 4 or pH 7 buffer for at least an hour before calibrating 11 3 3 Checking the Reference Electrode Some processes contain substances for example sulfides that poison the reference electrode Poisoning alters the electrode potential For example sulfide poisoning converts the reference electrode from a silver silver chloride elec trode into a silver silver sulfide electrode causing a shift in potential of several hundred millivolts A good way to check for poisoning is to compare the voltage of the reference electrode with a silver silver chloride electrode that is known to be good The reference electrode from a new sensor is the best choice To check the sus pect electrode place both sensors in a beaker containing buffer or a solution of potassium chloride Connect the ref erence leads to a voltmeter and measure the potential difference If the suspect electrode is good the difference should be no more than about 20 mV Refer to Figure 11 2 A poisoned reference electrode usually requires replace ment Reference lea
125. e the editing keys to change the display to the desired output dampening The range is 0 to 255 Press ENTER to save Press EXIT twice to return to the process display 59 MODEL 3081 pH ORP SECTION 8 0 8 4 DIAGNOSTIC PARAMETERS 8 4 1 Purpose PROGRAMMING FOR pH MEASUREMENTS This section describes how to do the following OPTIONAL OF F O o change the standardization or reference offset PROCEDURE enable and disable sensor diagnostics enable and disable glass impedance temperature compensation set the high and low warning and failure limits for the glass electrode set the high and low warning and failure limits for the reference electrode 8 4 2 Definitions 1 STANDARDIZATION REFERENCE OFFSET The transmitter reading can be changed to match the reading of a sec ond pH meter If the difference converted to millivolts between the transmitter reading and the desired value exceeds the programmed limit the transmitter will not accept the new reading To estimate the millivolt difference multiply the pH difference by 60 Refer to Section 7 6 Manual Calibration for additional information The standardization offset is also the absolute value of the actual cell voltage in pH 7 buffer For certain types of non glass pH electrodes the off set in pH 7 buffer may be as great as 800 mV To accommodate non glass electrodes the offset must be changed from the default value of 60 millivolts GLASS IMPEDANCE TEMPERA
126. e until the TEST function is disabled 2 The main display continues to show the ORP of the process stream The word HOLD appears in the display 3 The test current value supersedes both the HOLD value and the FAULT value 4 f fault occurs while the transmitter is generating the test current the word FAULT appears in the display and the display flashes 10 7 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the SIM OUtPUt sub menu appears Press ENTER The tESt prompt appears Use the editing keys to change the number to the desired value The allowed values are between 3 80 mA and 22 00 mA 00 ENTER 4 Press ENTER to start the test current To end the test current press EXIT Press EXIT to return to the process display 84 MODEL 3081 pH ORP SECTION 11 0 MAINTENANCE SECTION 11 0 MAINTENANCE 11 1 Overview 11 2 Transmitter Maintenance 11 3 pH Sensor Maintenance 11 4 Sensor Maintenance 11 5 Calibration 11 1 OVERVIEW This section gives general procedures for routine maintenance of the 3081 pH ORP transmitter and pH and ORP sensors The transmitter needs almost no routine maintenance Sensors require periodic inspection and cleaning The calibration of the transmitter sensor combination should be checked regularly and the loop recalibrated if necessary 11 2 TRANSMITTER MAINTENANCE Periodically clean the transmitter window with household ammonia or glass clea
127. ears If the security code is incor rect the process display reappears 5 7 3 Retrieving a Lost Security Code 1 If the security code has been forgotten enter 555 at the Id prompt and press ENTER The transmitter will display the present code Press EXIT to return to the process display Press PROG or CAL The Id screen appears Use the editing keys to enter the security code just shown then press ENTER The first sub menu under the selected menu will appear 41 MODEL 3081 pH ORP SECTION 6 0 OPERATION WITH MODEL 275 SECTION 6 0 OPERATION WITH MODEL 275 6 1 Note on Model 275 HART Communicator 6 2 Connecting the HART Communicator 6 3 Operation 6 1 Note on Model 275 HART Communicator The Model 275 HART Communicator is a product of Rosemount Measurement This section contains selected information on using the Model 275 with the Rosemount Analytical Model 3081 pH ORP Transmitter For complete information on the Model 275 Communicator see the Model 275 instruction manual For technical support on the Model 275 Communicator call Rosemount Measurement at 800 999 9307 within the United States Support is available worldwide the internet at http rosemount com 6 2 Connecting the HART Communicator Figure 6 1 shows how the Model 275 HART Communicator connects to the output lines from the Model 3081 pH ORP Transmitter A CAUTION For intrinsically safe CSA and FM wiring connections see the Model 275 inst
128. eature When the reference electrode impedance goes above the fault value the transmitter displays the diagnostic message rEFFAIL and sets a fault condition Press ENTER to save 80 MODEL 3081 pH ORP 2040 8000 SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 8 The rWH prompt appears In the display W appears as u Use the editing keys to change the display to the desired reference electrode high impedance warn ing value The allowed ranges are Type of reference electrode Allowed range Low impedance LO in step 6 0 2000 kilohms High impedance HI in step 6 0 2000 megohms Entering 0000 disables the feature When the reference electrode impedance goes above the fault value the transmitter displays the diagnostic message rEFWArn Press ENTER to save The rWL prompt appears Use the editing keys to change the display to the desired reference electrode low impedance warning value The allowed ranges are Type of reference electrode Allowed range Low impedance LO in step 6 not applicable High impedance HI in step 6 0 900 megohms Entering 0000 disables the feature When the reference electrode impedance goes below the warning value the transmitter displays the diagnostic message rEFWArn Press ENTER to save The prompt appears but is disabled when LO is selected in step 6 The rFL prompt appears Use the editing keys to change the display to the desired reference electrode low impedance f
129. ece D 2 1 3 Specifications General for Model 3081 3 1 4 Specifications ume 4 1 5 Specifications ORP 4 1 6 Ordering Information 4 2 0 INSTALLATION 7 2 1 Unpacking ul k ierant rr deu c 7 2 2 Pre Installation Set 7 2 3 Orienting the Display utk a auqa 10 2 4 Mechanical iiiter 10 2 5 Power Supply Current nnn entrent 13 3 0 uli ce 14 3 1 General uuu 14 3 2 Wiring Diagrams for pH Sensors sss 15 4 0 INTRINSICALLY SAFE AND EXPLOSION 31 4 1 Intrinsically Safe Installations I 31 4 2 Explosion 31 5 0 OPERATION WITH REMOTE CONTROLLER 37 5 1 D play uuu 37 5 2 Infrared Remote Controller IRC
130. ecent fault message appears in the display Press NEXT repeatedly to scroll through the stored messages The transmitter only remembers the three most recent messages nonE appears if there are no faults Pressing EXIT clears all the stored messages and returns the transmitter to the ShoW Flt display If the transmitter loses power all stored warning and fault messages are lost NO 8 Press EXIT to return to the process display 12 8 TESTING THE TRANSMITTER BY SIMULATING THE pH 12 8 1 General This section describes how to simulate a pH input into the 3081 pH ORP transmitter pH is directly proportional to voltage To simulate the pH measurement connect a standard millivolt source to the transmitter If the transmitter is working prop erly it will accurately measure the input voltage and convert it to pH Although the general procedure is the same the wiring details depend on the location of the preamplifier Consult the table to find the correct procedure Sensor Model 381 onl 12 8 4 Sensor all other models 12 8 5 110 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 8 2 pH Simulation When the Preamplifier Is Located in the MODEL 3081pH ORP Transmitter TRANSMITTER 1 2 3 Verify that switch S 1 is set to transmitter See Section 2 2 Turn off sensor diagnostics See Section 8 4 SO pH GND GUARD pH IN Turn off automatic temperature compensation Set manual temperature compensation to 25 See
131. ection 7 4 If the second calibration was successful an error was made during the first attempt If the second calibration fails go to step B B There is a remote possibility of a problem with the autocalibration program Repeat the calibration using the manual calibration procedure in Section 7 6 If manual calibration was successful when autocalibration failed the problem might be with the sensor electronics Call the factory for assistance If manual calibration is not possible go to step C C Check transmitter performance by simulating pH inputs See Section 12 8 If the transmitter performs satisfactorily go to step D If the transmitter does not respond to simulated inputs replace the board stack PN 23574 02 D Ifthe transmitter responds to simulated inputs the problem must lie with the sensor or the interconnecting wiring Verify the interconnecting wiring point to point Fix or replace bad cable If cable is good replace the pH sensor 12 4 11 Std Err Std Err means the reference electrode voltage has changed drastically Typical causes are exposure to poisoning agents sulfides or cyanides or prolonged exposure to high temperature Troubleshooting Flowchart Std Err Troubleshooting depends on the type of sensor If the sensor is rebuildable Replenish the electrolyte solution and replace the liquid junction Calibrate the sensor Et the sensor can be calibrated the problem has been corrected If the sensor cannot b
132. either the junction box or the sensor Junction boxes can be attached to the sensor or installed some distance away If the junction box is not attached to the sensor it is called a remote junction box In most junction boxes used with the Model 3081 pH ORP a flat black plastic box attached to the same circuit board as the terminal strips houses the preamplifier The preamplifier housing in the 381 sensor is crescent shaped If the sensor is wired directly to the transmitter the preamplifier can be in the sensor or in the transmitter If the sensor cable has a GREEN wire the preamplifier is in the sensor If there is no green wire the sensor cable will contain a coax ial cable A coaxial cable is an insulated wire surrounded by a braided metal shield Depending on the sensor model the coaxial cable terminates in either a BNC connector or in a separate ORANGE wire and CLEAR shield 2 2 5 Changing Switch and Jumper Positions If the sensor and installation does not match the transmitter default settings in Section 2 2 1 change the settings to the correct values 1 Refer to Figure 2 1 2 Loosen the cover lock nut until the tab disengages from the front cover Unscrew the cover 3 Remove the three bolts holding the circuit board stack 4 Lift out the display board Do not disconnect the ribbon cable between it and the CPU board The CPU and analog boards are joined by a pin and socket connector along the bottom edge of the boards Carefully d
133. ent LCD 0 3 in 7 mm high Display board can be rotated 90 degrees clockwise or counterclockwise During calibration and programming messages and prompts appear in the temperature output area Power Supply and Load Requirements See graph below A minimum loop resistance of 250 Q and a minimum power supply voltage of 18 Vdc is required for HART communication Maximum power supply voltage for intrinsically safe and explosion proof operation is 42 4 Vdc minimum voltage and load for HART communication o lt 9 750 SECTION 1 0 DESCRIPTION AND SPECIFICATIONS Security User selected security code prevents accidental changes to program settings Ambient Temperature 4 to 149 F 20 to 65 C Relative Humidity 0 to 95 with covers sealed Storage Temperature 22 to 176 F 30 to 80 C EMI RFI Meets the requirements of EN50081 1 C EN50081 2 Hazardous Area Classification Explosion Proof FM Class I Div 1 Groups B C amp D Class II Div 1 Groups E F amp G Class Ill Div 1 CSA Class Div 1 Groups C amp D Class Div 2 Groups C amp D Class Div 2 Groups E F amp Class Ill Div 1 Intrinsic Safety FM Class Il Div 1 T4 T AMB 40 C T3AT AMB 70 C CSA Class Div 1 T T AMB 40 T3 T AMB 80 C CENELEC EEx ia IIC T5 Tamb 40 C T4 Tamb 65 C Non Incendive FM Class Div 2 Groups A B C amp D CSA Class
134. er the product of the hydroxide and hydrogen concentra tions remains constant Physical and chemical measurements made in real solutions are usually different from the values predicted from the behavior in ideal solutions Activity is a way of accounting for the discrepancy For ions in solution ideal behavior occurs at infi nite dilution Infinite dilution means the solution contains so few ions that they behave independently of one another As the concentration of the ions increase they start to interact and the properties of the solution begin to deviate from the ideal The ratio of the true value to the ideal value at a given concentration is the activity coefficient The product of the activity coefficient and the concentration is the activity For electrolytes the activity is always less than the concentration The alkalai metals are lithium sodium potassium and cesium They form ions having unit positive charge lon exchange reactions involving alkalai metal ions cause certain types of glass to develop electrical potentials in the presence of hydrogen ions AMS is an acronym for Asset Management Solutions AMS is software running in Windows 95 that allows the user sitting at a computer to view process measure ments program transmitters and review maintenance and performance records The sensing element in a Balco RTD is an alloy containing 7096 nickel and 3096 iron Balco RTDs are identified by their resistance at 25 C The resis
135. er correcting wiring errors the glass impedance is still high go on to step 2 2 Inspect and clean the sensor Refer to Section 11 3 After cleaning the sensor calibrate it following the auto calibration procedure in Section 7 5 Be sure to note the sensor slope If cleaning the sensor lowers the impedance below 800 megohms a The sensor is in good condition b Return the calibrated sensor to service If cleaning does not lower the glass impedance and the sensor can be calibrated a The sensor is probably in good condition however it may be nearing the end of its life The electrode slope is a good indicator of remaining life SLOPE CONDITION OF SENSOR 54 60 mV unit pH Sensor is in good condition 48 50 mV unit pH Sensor is nearing the end of its life Once the slope drops below 48 mV unit pH the sensor can no longer be calibrated b The Glass Fail High GFH limit is probably set too low for the sensor Set the GFH limit to about 150 megohms greater than the measured glass impedance c lf the GLASSWArn message was also flashing raise the GWH limit from its former value by the same amount GFH was raised from its former value If cleaning does not lower the glass impedance and the sensor cannot be calibrated The sensor has failed and should be replaced If the glass impedance is moderate between 40 and 800 megohms 1 The sensor may be dirty in which case cleaning it will lower the impedance reading The sen
136. er measures the voltage and uses a temperature dependent factor to convert the voltage to pH Because the cell has high internal resistance the pH meter must have a very high input impedance pH Meter Reference Electrode Temperature Sensor Measuring Electrode Test Solution FIGURE 13 1 pH Measurement Cell The cell consists of a measuring and reference electrode The voltage between the elec trodes is directly proportional to the pH of the test solution The proportionality constant depends on temperature so a temperature sensor is also necessary Figure 13 1 shows separate measuring and reference electrodes In most process sensors the electrodes and the tem perature element are combined into a single body Such sensors are often called combination electrodes The cell voltage is the algebraic sum of the potential of the measuring electrode the potential of the reference electrode and the liquid junction potential The potential of the measuring electrode depends only on the pH of the solution The potential of the reference electrode is unaffected by pH so it provides a stable reference voltage The liquid junction potential depends in a complex way on the identity and concentration of the ions in the sample It is always present but if the sensor is properly 114 MODEL 3081 pH ORP designed the liquid junction potential is usually small and rel atively constant All three potentials depend on temperature As discussed in
137. erature is correct the transmitter is working properly If the measured temperature is incorrect calibrate the transmitter against the standard resistance equivalent to 25 C See Section 7 4 for the procedure Change the resistance and verify that the temperature reading changes to the correct value If the transmitter works properly after temperature calibration the original calibration was in error Re attach the RTD wires and check the temperature performance of the sensor If the reading is still wrong the transmitter electronics have failed Replace the electronic board stack PN 23574 02 12 4 7 LInE FAIL LInE FAIL almost always means that the transmitter is measuring an incorrect resistance between terminal TB 3 RTD RTN and TB 4 RTD SNS These terminals are critical connections for the three wire RTD measurement Figure 12 3 shows a three wire RTD connection Troubleshooting Flowchart LInE FAIL A Checkfor miswires and open connections at TB 3 and TB 4 Open connections can be caused by loose connections poor spade crimps or broken wires Be sure to check junction boxes for proper pass through of all wires See Section 3 0 for junction box wiring If correcting a wiring problem makes the message disappear the system is in good condition If the message is still showing go to step B 97 MODEL 3081 pH ORP SECTION 12 0 B TROUBLESHOOTING The RTD sense or the RTD return wire inside the sensor cable may be broken
138. es The main display will show the measured pH of the buffer based on the previous calibration Press ENTER bF2 flashes until the pH reading is stable If the pH reading is not stable after 20 minutes the transmitter automatically leaves the CALIBRATE menu and returns to process mode If this happens consult Section 12 5 Troubleshooting for assistance Once the reading is stable the display changes to look like the figure at the left The flashing number is the nominal pH that is the pH of the buffer at 25 C If the flashing number does not match the nominal pH press N or qp until the correct pH appears Press ENTER to save the second calibration point The calibration is complete but the transmitter remains in the CALIbrAtE sub menu for two minutes after ENTER is pressed Remove the sensor from the buffer and return it to the process If the transmitter was in hold during calibration wait until readings have stabilized before taking the transmitter out of hold See Section 7 3 Using the Hold Function The transmitter uses the calibration data to calculate a new slope Refer to Section 13 7 Buffers and Calibration for more details If the slope is unacceptable the calibration will not be updated and the transmitter will display a SLOPE Err HI or SLOPE Err LO error message Refer to Section 12 5 Troubleshooting for assistance To leave the CALIBRATE menu press EXIT For quality control and troubleshooting it is helpful to k
139. es and open connections particularly at TB 10 Open connections can be caused by loose connections poor spade crimps or broken wires Be sure to check junction boxes for proper pass through of all wires See Section 3 0 for junction box wiring E correcting a wiring problem clears the message the system is in good condition If the message is still showing go to step B Check that the transmitter is working properly by simulating a pH input See Section 12 8 If the transmitter does not respond to simulated inputs replace the board stack PN 23574 02 If the transmitter performs satisfactorily and the preamplifier is located in a remote junction box or in a sensor mounted junction box go to step C If the transmitter performs properly and the preamplifier is located in the transmitter the sensor has failed and should be replaced The problem may lie with the remote preamplifier or with the cable connecting the preamplifier and junction box to the transmitter 1 Be sure all wires between the junction box and the transmitter are connected 2 Use Rosemount Analytical cable Generic cable may not work Refer to Section 3 0 for part numbers If the diagnostic message clears the interconnecting cable was the problem If the message remains go to step D Confirm that the problem is with the remote preamplifier Wire the pH sensor directly to the transmitter Move switch S 1 to the transmitter position for the test and return it to the
140. es in the sensor cable A GREEN wire means the preamplifier is in the sen sor An coaxial cable means the preamplifier is in the transmitter A coaxial cable is an insulated wire surrounded by a braided metal shield The wire terminates in either a BNC connector or an ORANGE wire with a CLEAR shield Write the preamplifier location here CAN YOU USE THE QUICK START GUIDE ON THE FOLLOWING PAGE Use the Quick Start Guide if you are NOT using a HART communicator you do NOT require an intrinsically safe or explosion proof installation you are NOT measuring ORP you do NOT require transmitter setup beyond programming the 4 20 mA output you are NOT using a a sensor mounted junction box or a remote junction box you are NOT using a sensor made by another manufacturer m c you are using one of the following sensors Base Model Model Option note 381 55 381 52 385 03 385 04 396P 02 54 3965 01 55 396 02 55 3968 54 Note Only the model option numbers needed to select the correct wiring diagram in the Quick Start Guide are shown Other model option numbers are not shown If you cannot use the Quick Start Guide turn to Section 2 0 of the instruction manual QUICK START GUIDE FOR MODEL 3081pH ORP Before using this Quick Start Guide please read WHAT YOU NEED TO KNOW BEFORE INSTALLING AND WIRING A ROSEMOUNT ANALYTICAL SENSOR TO THE MODEL 3081 pH ORP TRANSMITTER on the preceding page Section
141. estimate the time in minutes required for the output to read 95 of the final reading following a step change divide the setting by 20 Thus a setting of 140 means that following a step change the output takes about seven minutes to reach 95 of final read ing The output dampen setting does not affect the response time of the process display The maximum setting is 255 77 MODEL 3081 pH ORP cOonA EXIT 78 NEXT ENTER NEXT ENTER 400 NEXT ENTER 00 ENTER SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 3 3 Procedure 1 Enter the Program menu by pressing PROG the IRC The OutPut sub menu appears Press ENTER The screen displays the 4 MA prompt Use the editing keys to change the displayed number to the desired ORP The allowed range is 1400 to 1400 To change the display to a negative number press or until no digit is flashing Then press or v until the minus sign appears To change the display to a positive number press 3 or until the negative sign is flashing Then press or until the minus sign disappears Press ENTER to save The screen displays the 20 MA prompt Use the editing keys to change the displayed number to the desired ORP The allowed range is 1400 to 1400 Press ENTER to save The screen displays the HoLd prompt Use the editing keys to change the display to the output desired when the tra
142. factured by Rosemount Analytical the RTD IN lead is red and the RTD RTN lead is white For the Model 399 33 ORP sensor the leads are black and white The Model 328A sensor has no RTD The Model 320HP system has a readily identifiable separate temperature element Resistance at room temperature for common RTDs is given in the table If the resistance is the temperature element is a about 110 ohms Pt 100 RTD about 1100 ohms Pt 1000 RTD about 3000 ohms 3K Balco RTD 2 2 3 Reference Electrode Impedance The standard silver silver chloride reference electrode used in most industrial and laboratory pH electrodes is low imped ance EVERY pH and ORP sensor manufactured by Rosemount Analytical has a low impedance reference Certain spe cialized applications require a high impedance reference electrode The transmitter must be programmed to recognize the high impedance reference MODEL 3081 pH ORP SECTION 2 0 INSTALLATION 2 2 4 Preamplifier Location pH sensors produce a high impedance voltage signal that must be preamplified before use The signal can be preampli fied before it reaches the transmitter or it can be preamplified in the transmitter To work properly the transmitter must know where preamplification occurs Although ORP sensors produce a low impedance signal the voltage from an ORP sensor is amplified the same way as a pH signal If the sensor is wired to the transmitter through a junction box the preamplifier is ALWAYS in
143. fault messages to aid in trouble shooting The electrolyte solution inside an electrode is called the filling solution The buffered electrolyte solution inside a glass electrode is usually called the internal filling solution The solution inside the reference electrode is usually called the external filling solution or simply the filling solution In many industrial reference electrodes the filling solution is not a liquid but is a semi solid gel Glass imped ance The overall resistance of the glass membrane to the flow of current Glass impedance is a strong function of temperature Impedance increases as temper ature decreases Temperature corrected glass impedance is a valuable diagnos tic tool Abnormally low impedance implies a cracked or broken glass membrane High impedance suggests that the electrode is nearing the end of its life pH measuring electrodes are often called glass electrodes The electrode is a piece of glass tubing that has a pH sensitive glass membrane blown onto the end The tube is filled with a buffered solution of potassium chloride A silver wire coat ed with silver chloride contacts the fill solution and the silver wire is connected to the electrode lead wire The entire electrode is sealed Glass refers to the pH sensitive glass membrane in the sensor The glass membrane is the pH sensitive glass piece blown onto the bottom of the glass tube that forms the body of the glass electrode The pH sensitive glass
144. ference electrodes In most process sensors the electrodes and the temperature element are combined into a single body Such sensors are often called combination electrodes The cell voltage is the algebraic sum of the potential of the measuring electrode the potential of the reference elec trode and the liquid junction potential The potential of the measuring electrode depends on the ORP of the solu tion The potential of the reference electrode is unaffected by ORP so it provides a stable reference voltage The liquid junction potential depends in a complex way on the identity and concentration of the ions in the sample It is always present but if the sensor is properly designed the liquid junction potential is usually small and relatively constant All three potentials depend on temperature The construction of each electrode and the electrical potential associated with the electrode are discussed in Sections 14 2 14 3 and 14 4 120 MODEL 3081 pH ORP 14 2 MEASURING ELECTRODE Figure 14 2 shows a typical ORP measuring elec trode The electrode consists of a band or disc of platinum attached to the base of a sealed glass tube A platinum wire welded to the band connects it to the lead wire For a noble metal electrode to develop a stable potential a redox couple must be present A redox couple is simply two compounds that can be con verted into one another by the gain or loss of elec trons Iron 1 and iron III are a redox
145. ference impedance is low lt 70 kilohms a The reference electrode is in good condition pH sensors manufactured by Rosemount Analytical use low impedance silver silver chloride reference electrodes b The reference failure high RFH limit is probably set too low Change the limit to a value about 50 kilohms greater than the measured reference impedance If rEF WARN was also displayed change the reference warning high RWH limit to about 25 kilohms above the measured reference impedance If the reference impedance is high gt 70 kilohms 1 The sensor may be dirty in which case cleaning it will lower the impedance If the sensor is rebuildable the reference electrolyte may be depleted Finally the sensor may be in good condition The warning and failure limits are simply set too high 2 Inspect and clean the sensor Refer to Section 11 3 If the sensor is rebuildable replace the reference junction and replenish the electrolyte solution Refer to the sensor instruction manual for details Check the reference impedance again If cleaning the sensor reduces the impedance a The sensor is in good condition Calibrate the sensor and return it to the process b Change the reference failure high RFH limit to a value about 50 kilohms greater than the measured reference impedance If rEF WARN was also displayed change the reference warning high RWH limit to about 25 kilohms above the measured reference impedance If cleaning
146. g temperature remains constant any change in cell voltage is caused solely by a change in the pH of the sample Therefore the cell voltage is a measure of the sample pH Note that a graph of equation 1 E T plotted against pH is a straight line having a y intercept of and a slope of 0 1984 T 13 6 GLASS ELECTRODE SLOPE For reasons beyond the scope of this discussion equation 1 is commonly rewritten to remove the temperature dependence in the intercept and to shift the origin of the axes to pH 7 The result is plotted in Figure 13 6 Two lines appear on the graph One line shows how cell voltage changes with pH at 25 C and the other line shows the rela tionship at 50 C The lines which are commonly called isotherms intersect at the point pH 7 0 mV An entire family of curves each having a slope determined by the temperature and all passing through the point pH 7 0 mV can be drawn on the graph FIGURE 13 6 Glass Electrode Slope The voltage of a pH measurement cell depends on pH and temperature A given pH produces different voltages depending on the temperature The further from pH 7 the greater the influence of temperature on the relationship between pH and cell voltage Figure 13 6 shows why temperature is important in making pH measurements When temperature changes the slope of the isotherm changes Therefore a given cell voltage corresponds to a different pH value depending on the temperature For examp
147. g pumps The transmitter output can be programmed to remain at the last value or to generate any current between 3 80 and 22 0 mA During hold the transmitter displays the present ORP and temperature The word HOLD appears in the display FAULT A fault is a system disabling condition When the transmitter detects a fault the fol lowing happens a The display flashes b The words FAULT and HOLD appear in the main display c Afault or diagnostic message appears in the temperature current display area d The output signal remains at the present value or goes to the programmed fault value Permitted values are between 3 80 and 22 00 mA e If the transmitter is in HOLD when the fault occurs the output remains at the programmed hold value To alert the user that a fault exists the word FAULT appears in the main dis play and the display flashes A fault or diagnostic message also appears f Ifthe transmitter is simulating an output current when the fault occurs the transmitter con tinues to generate the simulated current To alert the user that a fault exists the word FAULT appears in the display and the display flashes 0 lfasensor fault occurs a 1 mA signal appears at TB 14 see Section 2 5 2 Sensor faults are rEF FAIL rEF WArn GLASSFAIL and GLASSWARrn See Section 12 0 for more information about sensor faults DAMPEN Output dampening smooths out noisy readings But it also increases the response time of the output To
148. gohms HI 0 to 2000 kilohms LO 0 to 2000 megohms HI 0 to 2000 kilohms LO to 900 megohms FACTORY SETTINGS USER SETTINGS 1400 mV 1400 mV 21 00mA 0 seconds 22 00mA 60 mV Off Off LO 1500 megohms 140 kilohms 1000 megohms 40 kilohms 20 megohms Does not apply for low impedance reference cell 0 to 900 megohms 10 megohms Does not apply for low impedance reference cell 100 3 100 4 1000 3 1000 4 3000 pH ORP C F mA of full scale 0 to 999 3 80 to 22 00 mA 100 3 pH C mA 000 12 00 mA MODEL 3081 pH ORP IMPORTANT SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 3 OUTPUT RANGING 10 3 1 Purpose This section describes how to do the following 1 2 3 4 assign ORP values to the 4 and 20 mA outputs set the output current generated by the transmitter during hold set the output current generated by the transmitter when a fault is detected control the amount of dampening on the output signal 10 3 2 Definitions 1 CURRENT OUTPUTS The transmitter provides a continuous 4 20 mA output directly pro portional to the measured ORP Any ORP value between 1400 and 1400 mV can be assigned to the low output 4 mA and the high output 20 mA HOLD During calibration and maintenance the transmitter output may be outside the normal operating range Placing the transmitter on hold prevents false alarms or the unwanted oper ation of chemical dosin
149. hanging settings use a different security code for each nearby transmitter See Section 5 7 Security NOTE During calibration the sensor may be exposed to solutions hav ing ORP outside the normal range of the process To prevent false alarms and possible undesired operation of chemical dos ing pumps place the analyzer in hold during calibration See Section 9 3 Using the Hold Function for details EXIT NEXT ENTER 9 5 3 Procedure 1 Place the transmitter in ORP mode See Section 10 6 3 steps 1 3 After selecting and saving OrP press EXIT twice to return to the main display 2 Enter the CALIBRATE menu by pressing CAL on the IRC The Std sub menu appears NEXT ENTER 3 Rinse the sensor with deionized water and place it in the ORP standard along with a thermometer Submerge the sensor tip at least three inches below the surface of the liquid Swirl the sensor to dislodge trapped air bubbles The main display will show the measured ORP based on the previous calibration Std 4 Once the temperature and ORP readings are stable press ENTER The screen changes to look like the figure to the left EXIT NEXT ENTER 5 Use the editing keys to change the flashing display to the desired ORP read ing Press ENTER to save 6 Press EXIT to return to the main display 74 MODEL 3081 pH ORP SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS SECTION 10 0 PROGRAMMING FOR ORP MEASURE
150. iagrams for Model 399 5 15 3 2 Wiring Diagrams for Model 397 15 3 3 Wiring Diagrams for Model 396R Sensors 15 3 4 Wiring Diagrams for Model 396P Sensors 16 3 5 Wiring Diagrams for Model 396 5 16 3 6 Wiring Diagrams for Model 389 5 16 3 7 Wiring Diagrams for Model 385 Sensors sss 17 3 8 Wiring Diagrams for Model 381 17 3 9 Wiring Diagrams for Model 381pHE and 381pH Sensors 17 3 10 Wiring Diagrams for Model 328A Sensors 9 17 3 11 Wiring Diagrams for Model 320HP 17 8 1 PI SOTO SUIS 57 8 2 pH Values of Standard Buffer Solutions and the Temperature Range over which PH Values Deflried uu l nre de ene de 67 8 3 pH Values of Commercial technical Buffers and the Temperature Range over which pH Values are Defined 68 8 4 Standard and Technical Buffers Recognized by the Model 3081 pH Transmitter 68 10517 ORP IDIBUS 76 11 1 Replacement Parts for Model 3081 pH Transmitter 86 12 1 R
151. ials of the two electrodes Electrochemistry is the study of charge transfer across boundaries The charge being transferred can be ions or electrons An electrode is a two phase system where the charge transfer across the interface involves electrons A real physical electrode may incorporate several boundaries An electrolyte is a substance that when dissolved in water produces an apprecia ble concentration of ions Most salts mineral acids sulfuric acid hydrochloric acid phosphoric acid and nitric acid and most bases are electrolytes Error is a measure of how closely a measured value agrees with the true value In cases where a true value is not known error usually refers to the difference between the measured and the generally accepted value An error condition Std Err SLOPE Err LO or SLOPE Err HI occurs during cali bration if standardization offset or the slope exceeds programmed values An enclosure is explosion proof if it can withstand an internal explosion without rupturing and without causing the the ignition of the gas surrounding the enclo sure 129 MODEL 3081 pH ORP Fault Filling solution Glass electrode Glass membrane Ground Ground loop Half reaction HART 130 SECTION 16 0 GLOSSARY A fault is a system disabling condition Measurement data displayed during a fault condition are probably in error and should be regarded with great suspicion The Model 3081 pH ORP transmitter displays
152. igh impedance HI in step 11 0 900 megohms Entering 0000 disables the feature When the reference electrode impedance goes below the fault value the transmitter displays the diagnostic message rEFFAIL and sets a fault condition Press ENTER to save The prompt appears but is disabled when LO is selected in step 11 16 Press EXIT to return to the process display 63 MODEL 3081 pH ORP IMPORTANT 64 SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 5 TEMPERATURE RELATED SETTINGS 8 5 1 Purpose This section describes how to do the following 1 activate and deactivate automatic temperature compensation 2 seta manual temperature compensation value 3 match the transmitter to the type of temperature element in the pH sensor 8 5 2 Definitions 1 AUTOMATIC TEMPERATURE COMPENSATION The transmitter uses a temperature dependent factor to convert measured cell voltage to pH In automatic temperature compen sation the transmitter measures the temperature of the process and automatically calculates the correct conversion factor For maximum accuracy use automatic temperature compensa tion See Section 13 6 Glass Electrode Slope for more information 2 MANUAL TEMPERATURE COMPENSATION In manual temperature compensation the transmitter uses the programmed temperature to convert measured voltage to pH It does not use the actual process temperature Do NOT use manual temperature compensation unless the process temperature varies
153. ight arrow keys move the cursor one digit at a time across a num ber The up and down arrow keys increase or decrease the value of the selected digit The up and down arrow keys also scroll the display through the items in a list CAL Press to access the calibrate menu PROG Press to access the program menu DIAG Press to view diagnostic mes sages Pressing CAL PROG or DIAG causes the program screen to appear with the selected menu CALIBRATE PROGRAM OR DIAGNOSE showing See Figure 5 2 The first sub menu or the first diagnostic message also appears Figure 5 4 shows the complete menu tree REMOTE CONTROL HOLD Press to access the prompt that turns on or off the Hold function ENTER Press to advance from a sub menu to the first prompt under the sub menu Pressing ENTER also stores the selected item or value in memory and advances to the next prompt NEXT Press to advance to the next sub menu EXIT Press to end the current opera tion The transmitter returns to the first prompt in the present sub menu Changes will NOT be saved FIGURE 5 3 Infrared Remote Controller Hold the IRC within 6 feet of the transmitter and not more than 15 degrees from the center of the display window 38 MODEL 3081 pH ORP SECTION 5 0 OPERATION WITH REMOTE CONTROLLER 5 3 MENU TREE pH The Model 3081 pH transmitter has three menus CALIBRATE PROGRAM and DIAGNOSE Under the Calibrate and Program
154. ill not be updated and the transmitter will display a SLOPE Err HI or SLOPE Err LO error mes sage Refer to Sections 12 5 and 12 5 Troubleshooting for assistance 11 To leave the CALIBRATE menu press EXIT 12 For quality control and troubleshooting it is helpful to know the electrode slope To display the slope press CAL on the IRC The CALIbrAtE sub menu will appear Press NEXT The Std sub menu appears Press ENTER The Std prompt appears Press ENTER again SLOPE xx xx will appear in the display The four digit number is the electrode slope For a good sensor the slope is between 50 and 60 53 MODEL 3081 pH ORP 99222 OPTIONAL PROCEDURE 54 SECTION 7 0 CALIBRATION OF pH MEASUREMENTS 7 7 MAKING THE TRANSMITTER READING MATCH A SECOND pH METER STANDARDIZATION 7 7 1 Purpose 1 This section describes how to make the transmitter reading match the reading from a second pH meter The measurement made with the second meter is called the standard pH The process of making the two readings agree is called standardization This section also describes how to enter an independently determined slope into the transmitter 7 7 2 What Happens During Standardization 1 The user enters the pH reading from a second meter into the transmitter The transmitter changes the displayed pH to the new value The transmitter converts the difference between the pH readings ApH into
155. ion the transmitter calculates the correct buffer value and uses it in the calibration During manual cali bration the user must enter the correct pH value Buffers have limited shelf lives Do not use a buffer if the expiration date has passed Store buffers at controlled room temperature Do not return used buffer to the stock bottle Discard it Protect buffers from excessive exposure to air Atmospheric carbon dioxide lowers the pH of alkaline buffers Other trace gases commonly found in industrial environments for example ammonia and hydrogen chloride also affect the pH of buffers Molds from airborne spores grow readily in neutral and slightly acidic buffers Mold growth can substantially alter the pH of a buffer 10 Rinse the sensor with deionized water before placing it in a buffer Remove excess water from the sensor by gently daubing it with a clean tissue Do not wipe the sensor Wiping may gener ate a static charge leading to noisy readings The static charge may take hours to dissipate A few drops of deionized water carried with the sensor into the buffer will not appreciably alter the pH MODEL 3081 pH ORP SECTION 7 0 CALIBRATION OF pH MEASUREMENTS NOTE A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each nearby transmitter See Section 5 7 Security NOTE During calibration the sensor may be exposed to
156. ion is strongly recommended Auto calibra tion avoids common pitfalls and reduces errors For more information about calibration in pH measurements and the use of buffers refer to Section 13 7 Buffers and Calibration 7 5 2 What Happens During Auto Calibration 1 2 The transmitter displays prompts that guide the user through a two point buffer calibration The transmitter recognizes the buffers and uses the temperature corrected pH value in the cali bration The transmitter also measures noise and drift and does not accept calibration data until readings are stable Stability limits are user programmable See Section 9 7 Buffer Calibration Parameters 7 5 3 Use of Calibration Standards buffers 1 A pH measurement is only as good as the calibration and the calibration is only as good as the buffers used A careful buffer calibration is the first step in making an accurate pH measurement Calibrate with buffers having pH values that bracket the pH of the process For example if the pH is between 8 and 9 calibrate with pH 7 and 10 buffers Commercial buffers for intermediate range pH are readily available Buffers outside the range pH 3 0 to pH 10 0 may not be readily available and must be prepared by the user Tables 8 2 and 8 3 in Section 8 7 Buffer Calibration Parameters list the buffers that the transmitter recognizes Allow time for the sensor and buffers to reach the same temperature If the sensor was just removed fro
157. ion plug In a properly function ing electrode the resistance of the liquid junction should be no more than several hundred kilohms If the junction is plugged or if the filling solution or gel is depleted the resist ance increases A high reference impedance may also mean the sensor is not immersed in the process stream Glass impedance refers to the impedance of the pH sensi tive glass membrane The impedance of the glass mem brane is a strong function of temperature As temperature increases the impedance decreases For a change in glass impedance to have any meaning the impedance measurement must be corrected to a reference tempera ture The impedance of a typical glass electrode at 25 C is several hundred megohms A sharp decrease in the tem perature corrected impedance implies that the glass is cracked A cracked glass electrode produces erroneous pH readings The electrode should be replaced immediately A high temperature corrected glass impedance implies the sensor is nearing the end of its life and should be replaced as soon as possible SECTION 13 0 pH MEASUREMENTS 13 11 SHIELDS INSULATION AND PREAMPLIFIERS pH measurement systems cell and meter have high impedance The high impedance circuit imposes important restrictions on how pH measurement systems are designed The lead wire from the glass electrode connects two high resistances about 100 at the electrode and about 1 000 000 at the meter Theref
158. ircuit end cap loosen the lock nut until the tab disengages from the end cap then unscrew the cover 3 The transmitter has two 3 4 inch conduit openings one on each side of the housing Run sensor cable through the left side opening as viewed from the wiring terminal end of the transmitter and run power current loop wiring through the right side opening 10 MODEL 3081 pH ORP SECTION 2 0 INSTALLATION Use weathertight cable glands to keep moisture out of the transmitter 5 f conduit is used plug and seal the connections at the transmitter housing to prevent moisture from getting inside the transmitter NOTE Moisture accumulating in the transmitter housing can affect the performance of the trans mitter and may void the warranty 6 Ifthe transmitter is installed some distance from the sensor a remote junction box with preamplifier in the junction box or in the sensor may be necessary Consult the sensor instruction manual for maximum cable lengths 2 4 2 Mounting on a Flat Surface See Figure 2 4 MILLIMETER INCH TERMINAL BLOCK TB TERMINAL END CAP OMITTED THRI AP FOR CLARITY 2 PLACES p X THIS VIEW CIRCUIT TERMINAL END END 3 4 14 NPT 2 PLACES 2 PLACES SURFACE PLATE BY OTHERS 1 4 20 THREADS 4 PLACES FLAT SURFACE MOUNTING PAD HOLE PATTERN FIGURE 2 4 Mounting the Model 3081 pH ORP Transmitter on a Flat Surface 11 MODEL 3081 pH ORP SECTION 2 0 INSTALLATION 2
159. is usually a bulb but it can be flat Ground usually refers to either earth ground or a common Earth ground is the earth or a conducting body serving in place of the earth A common is a point in a circuit to which other voltages are compared The meaning intended is usually clear from the context A ground loop exists when a circuit is connected to earth ground at two or more points The potential of the earth varies from point to point so multiple connec tions to ground cause currents to flow If the current flows through a signal carry ing wire the result is a noisy offset signal In a typical process measurement the pH sensor is connected through the process liquid to earth ground If the circuit ry in the pH transmitter becomes connected to a second earth ground current will flow through the reference electrode A voltage proportional to the current and the electrode resistance develops across the reference electrode Because the volt age is in series with the other potentials in the cell the ground loop current caus es the pH reading to be substantially different from the expected value pH read ings affected by ground loops are often noisy as well A half reaction shows the gain or loss of electrons by a chemical species The half reaction for a silver silver chloride reference electrode is AgCl s e Ag s In the half reaction a silver ion in the silver chloride crystal gains an electron and becomes a silver
160. is 30 seconds 8 7 3 Procedure Press PROG on the infrared remote controller IRC NEXT ENTER Press NEXT until the bUFFEr sub menu appears Press ENTER The screen displays the bAUTO prompt Press or to activate On or deacti vate OFF auto calibration Press ENTER to save The screen displays the bUFFEr prompt Press or to select the desired buffer or buffers The buffer values available under each designation are given in Table 8 4 Std Press ENTER to save TABLE 8 4 Standard and Technical Buffers Recognized by the 3081pH Transmitter NIST DIN 19266 JIS 8802 and BSM standard buffers Merck Buffers technical buffers Ingold Buffers technical buffers DIN 19267 technical buffers The screen changes to display the tIME prompt Use the editing keys to change the flashing number to the time in seconds the reading must remain stable for calibration data to be accepted The maximum is 30 seconds Press ENTER to save The screen changes to display the pH prompt Use the editing keys to change the flashing display to the pH range the reading must remain in for calibration data to be accepted The minimum range is 0 01 Press ENTER to save Press EXIT twice to return to the process display 68 MODEL 3081 pH ORP IMPORTANT IMPORTANT SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 8 ISOPOTENTIAL PARAMETERS 8 8 1 Purpose This section describes how to do the following 1 2 convert the pH
161. is slightly different The microprocessor calculates the equation of the straight line connecting the points The general form of the equation is E A B t 273 15 pH 7 2 The slope of the line is B t 273 15 where t is the tem perature in C and the y intercept is A If pH 7 buffer is used for calibration V7 equals A If pH 7 buffer is not used A is calculated from the calibration data cell voltage pH10 0 slope t 273 15 w y intercept pH7 0 mV FIGURE 13 7 Two Point Buffer Calibration The graph shows a calibration using pH 7 and pH 10 buffers The calibration equation is the straight line connecting the two points If temperature changes the slope changes by the ratio to 273 15 273 15 where 11 is the calibration tempera ture and t is the process temperature in C The calibration equations rotate about the point pH 7 A The microprocessor then converts subsequent cell voltage measurements into pH using the calibration line 13 8 ISOPOTENTIAL pH Frequently the calibration temperature and the process temperature are different Therefore the calibration slope is not appropriate for the sample Figure 13 7 shows what the microprocessor does when buffer and sample temper atures are different Assume the sensor was calibrated at temperature t and the process temperature is to To meas ure the pH of the process the microprocessor rotates the calibratio
162. isengage the CPU board from the analog board The analog board will remain attached to the transmitter body RIBBON CABLE INFRARED DETECTOR ANALOG BOARD CPU BOARD DISPLAY BOARD FRONT COVER FIGURE 2 1 Model 3081 pH ORP Transmitter Exploded Drawing of Circuit Board Stack MODEL 3081 pH ORP SECTION 2 0 INSTALLATION 5 Setthe jumpers and the slide switch on the analog board Refer to Figure 2 2 a Temperature element jumper Temperature element element PL 1000 RTD Pt 100 RTD Balco RTD b Reference impedance jumper Jumper position Reference impedance c Reference impedance jumper JP 5 Jumper position Reference impedance d Preamplifier location selection switch Move slider toward Preamplifier location edge of board center of board FACTORY INSTALLED ON JP5 PIN 4 ONLY The transmitter must also be programmed to recognize the RTD If pH is being measured see Section 8 5 If ORP is being measured see Section 10 5 If sensor diagnostics are to be used with a high impedance reference electrode the high impedance must be identified in the diagnostics setup program See Section 8 4 for pH measurements See Section 10 4 for ORP measurements Leave jumper connected on Pin 4 only unless a high impedance reference is used NOTE all standard sen Sors use low impedance references PREAMP SELECTION SLIDE SWITCH S SENSOR OR
163. iting keys to change the flashing display to the desired standardization reference offset in millivolts The range is 0 to 1000 mV Press ENTER to save The prompt appears Use the or v keys to enable On or disable OFF the sensor diagnostics Press ENTER to save ENTER The IMPtC prompt appears Use the keys to enable On or disable OFF glass impedance temperature compensation Because glass impedance is a strong function of InP C temperature correcting glass impedance for temperature is recommended A third set ESL a ting SPC appears in addition to On and OFF Do not select SPC the setting is intend ed for factory use Press ENTER to save PROGRAM The rEF prompt appears Press or until the desired setting appears LO identifies a low impedance reference electrode and HI identifies a high impedance reference electrode Press ENTER to save Selecting LO disables the low impedance warning and failure limits for the reference electrode NOTE Be sure the jumpers on the analog board are set to match the reference electrode impedance See Section 2 2 Pre Installation Set Up The rFH prompt appears Use the editing keys to change the display to the desired ref erence electrode high impedance fault value The allowed ranges are Type of reference electrode Allowed range Low impedance LO in step 6 0 2000 kilohms High impedance HI in step 6 0 2000 megohms Entering 0000 disables the f
164. its 60 8 2 Suggested Warning and Failure Limits for Low Impedance Reference Electrodes 61 8 3 Suggested Warning and Failure Limits for High Impedance Glass Reference Electrodes ci 61 10 1 Suggested Warning and Failure Limits for Low Impedance Reference Electrodes 79 10 2 Suggested Glass Impedance Warning and Failure Limits for a Glass Reference T V 79 11 1 Exploded View of Model 3081 pH ORP 85 11 2 Checking the Potential of the Reference Electrode 87 12 4 Warning nnns 89 122 Fault AnnurnclallOns osos ioc 89 T2 3 ucciso citet ette orae NAO sassa 96 12 4 Temperature Simulation into the Model 3081 pH ORP Transmitter 97 12 5 Troubleshooting Flow Chart Preamplifier in Sensor Mounted Junction Box or emote Junction BOX euis ud uu dca 108 12 6 Troubleshooting Flow Chart Preamplifier in Transmitter or Built into Sensor 109 12 7 pH Simulation When the Preamplifier is Located in the Transmitter 111 12 8 pH Simulation When the Preamplifier is Located in a Remote Junction Box or in a Sensor Mounted Junction
165. itter ends the current operation without saving data and returns the transmitter to the process display Reset does not return the transmit ter to factory default setting RTD is an acronym for resistance temperature detector A salt bridge provides an electrical connection between two electrolyte solutions without permitting the solutions to mix The classic salt bridge is a U shaped tube filled with gelled potassium chloride and plugged at both ends with a porous mate rial When the ends are inserted in separate beakers an electrical connection is formed between the beakers See the definition of electrochemical cell A shield is a metal braid that encloses the insulated signal carrying wire The shield protects the signal wire from extraneous signals MODEL 3081 pH ORP Solution ground Solution temperature compensation Sub menu Standardization Temperature compensation Warning limit SECTION 16 0 GLOSSARY A solution ground is a metal post or ring incorporated into the sensor body and mak ing contact with the process stream Glass and reference impedances are meas ured by applying a voltage pulse between the electrode and the solution ground The pH of many solutions particularly alkaline ones is a function of temperature Therefore although the concentration of the chemical causing the pH remains constant pH will change if the temperature changes Solution temperature com pensation is a technique for converting pH
166. le assume the cell voltage is 150 mV At 25 C the pH is 9 54 and at 50 C the pH is 9 35 The process of select ing the correct isotherm for converting voltage to pH is called temperature compensation All modern process pH SECTION 13 0 pH MEASUREMENTS meters including the Model 3081pH ORP transmitter have automatic temperature compensation The slope of the isotherm is often called the glass electrode or sensor slope The slope can be calculated from the equation slope 0 1984 t 273 15 where t is tempera ture in C The slope has units of mV per unit change in pH The table lists slopes for different temperatures Temp C Slope mV unit pH 15 57 2 20 58 2 25 59 2 30 60 1 35 61 1 As the graph in Figure 13 6 suggests the closer the pH is to 7 the less important is temperature compensation For example if the pH is 8 and the temperature is 30 C a10 C error in temperature introduces a pH error of 0 03 At pH 10 the error in the measured pH is 0 10 13 7 BUFFERS AND CALIBRATION Figure 13 6 shows an ideal cell one in which the voltage is zero when the pH is 7 and the slope is 0 1984 T over the entire pH range In a real cell the voltage at pH 7 is rarely zero but it is usually between 30 mV and 30 mV The slope is also seldom 0 1984 T over the entire range of pH However over a range of two or three pH units the slope is usually close to ideal Calibration compensates for non ideal behavio
167. lead wires and for changes in wire resistance with temperature The Model 3081 transmitter can also be used with a two wire RTD Select a three wire configuration and jumper the RTD return and RTD sense terminals termi nals 3 and 4 respectively 10 5 2 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the tEMP sub menu appears in the display Press ENTER The screen shows the tC prompt Press or v to scroll to the desired tem perature element and wiring configuration Press ENTER to save 3 wire 1000 ohm RTD 4 wire 1000 ohm RTD 3 wire 100 ohm RTD 4 wire 100 ohm RTD 3000 ohm Balco RTD NOTE A jumper on the analog board must also be set to the appropriate RTD type See Section 2 2 Pre Installation Set Up 4 Press EXIT to return to the process display MODEL 3081 pH ORP NEXT ENTER SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 6 DISPLAY UNITS 10 6 1 Purpose This section describes how to do the following 1 2 3 4 switch the process display units between pH and ORP millivolts select C or F for the temperature display select percent of full scale or milliamps for the output display program a security code 10 6 2 Definitions 1 DISPLAY UNITS Select pH if the transmitter is being used to measure pH Select ORP if the transmitter is being used to measure ORP The units selected are shown in the main display next to the measured value OUT
168. lean pH sensor should not drift in buffer 12 5 6 Sensor Does Not Respond To Known pH Changes A Verify that the change really happened If pH response was being checked in buffers recheck performance with fresh buffers If a process pH reading was not what was expected check the performance of the sensor in buffers Also use a second pH meter to verify that the expected change in the process pH really occurred B Check the sensor Verify that wiring is correct Also the sensor may be dirty or aged or the reference junction may be depleted 1 Check that the sensor is properly wired to the transmitter See Section 3 0 Pay particular attention to terminals TB 10 mV in TB 7 reference and TB 8 solution ground 2 See Section 11 3 for cleaning procedures C clean properly wired sensor does not respond to pH changes the glass bulb is probably broken or cracked If a spare sensor is available check the spare If the spare sensor responds to pH changes the old sensor has failed If the spare sensor does not respond to pH changes go to step D If a spare sensor is not available check the glass impedance GIMP of the existing sensor See Section 12 7 If the impedance is less than about 20 megohm the pH glass is cracked Replace the sensor If the impedance is greater than about 20 megohm go to step D D Check transmitter performance by simulating pH inputs See Section 12 8 If the transmitter responds to simulated inputs
169. lity at 25 C 1 mV Resolution 1 mV and 0 1 C or F Stability at 25 C 0 25 per year The Model 3081 pH ORP Smart two wire microprocessor transmitter is housed in a NEMA 4X case Communication with the transmitter is through a hand held infrared remote controller a Model 275 HART communicator or any HART com patible device Automatic temperature compensation is standard and the transmitter can be programmed to convert meas ured pH to pH at 25 C solution temperature compensation Continuous sensor diagnostics are standard MODEL 3081pH ORP HART SMART TWO WIRE MICROPROCESSOR TRANSMITTER REQUIRED SELECTION LCD Infrared Remote Control included LCD Infrared Remote Control not included AGENCY APPROVALS FM approved intrinsically safe when used with approved sensor and safety barrier explosion proof CSA approved intrinsically safe when used with approved sensor and safety barrier explosion proof CENELEC approved intrinsically safe safety barrier required 3081pH 01 20 67 EXAMPLE MODEL 3081 pH ORP SECTION 1 0 DESCRIPTION AND SPECIFICATIONS MODEL 3081 pH ORP TRANSMITTER SENSOR COMPATIBILITY CHART PREAMPLIFIER LOCATION Sensor mounted Remote MODEL junction box junction box Transmitter 30 x Cd 820HP pa fof _ ______ 330B 328A 370 371 381pH 381pHE 381 381 385 385 389 396 396P 396R 397 398 398R 399 399 33 GP1 NOTE Preamplifier installed in junction box
170. lowed values are between 3 80 mA and 22 00 mA Press ENTER to start the test current To end the test current press EXIT Press EXIT to return to the process display 71 MODEL 3081 pH ORP SECTION 9 0 CALIBRATION OF ORP MEASUREMENTS SECTION 9 0 CALIBRATION OF ORP MEASUREMENTS 9 1 General 9 2 Entering and Leaving the Calibrate Menu 9 3 Using the Hold Function 9 4 Temperature Calibration 9 5 Standardization 9 1 GENERAL The Calibrate menu allows the user to calibrate the ORP and temperature response of the sensor The ORP calibration is a one point standardization against an ORP standard The temperature calibration is a one point standardization against a reference thermometer Prompts guide the user through the calibration proce dures 9 2 ENTERING AND LEAVING THE CALIBRATE MENU Press CAL on the infrared remote controller IRC to enter the Calibrate menu To store new settings in memory press ENTER To leave the Calibrate menu without storing new values press EXIT Pressing EXIT with a prompt showing returns the display to the first prompt in the sub menu Pressing EXIT a second time returns the transmitter to the process display If program settings are protected with a security code pressing PROG or CAL will cause the Id screen to appear Key in the security code and press ENTER The first sub menu will appear For more information see Section 5 7 Security A transmitter adjacent to the one being calibrated may
171. ly shows the basic measurement pH or ORP the temperature and the output signal Prompts guide the user through calibrating and programming the transmitter Prompts identify the parameter being edited and request the user to enter a num ber or to select a setting Reduction is the gain of electrons For example when an iron III ion becomes an iron Il ion it gains an electron Fe 3 e Fe A reference electrode maintains a stable potential independent of the pH or ORP of the sample The reference electrode also contains a reference junction that electrically connects the electrode with the sample The silver silver chloride elec trode is the most common reference electrode in industrial and laboratory appli cations The electrode consists of a piece of silver wire plated with silver chloride in contact with a solution of concentrated potassium chloride The reference impedance is the overall resistance of the reference electrode to the flow of current through it Generally as the reference junction becomes coat ed and plugged the reference impedance increases When the transmitter reading is forced to match the reading from a second pH meter the transmitter calculates the difference between its reading and the sec ond meter and converts the difference to voltage The difference is the reference offset If the reference offset exceeds the programmed limit the transmitter will not adjust the pH reading Resetting the transm
172. m a process having a temperature more than 10 C different from the buffer allow at least 20 minutes For best results calibrate with buffers having the same temperature as the process If the buffer and process temperature differ by more than about 15 C an error as great as 0 1pH may result Be careful using buffers at high temperatures Protect the solution from evaporation Evaporation changes the concentration of the buffer and its pH Be sure the pH of the buffer is defined at high temperatures The pH of many buffers is undefined above 60 C Finally no matter what the tem perature is allow the entire measurement cell sensor and solution to reach constant temperature before calibrating The pH of a buffer changes with temperature Equations relating pH to temperature for common buffers have been programmed into the Model 3081 pH transmitter During auto calibration the transmitter calculates the correct buffer value and uses it in the calibration Buffers have limited shelf lives Do not use a buffer if the expiration date has passed Store buffers at controlled room temperature Do not return used buffer to the stock bottle Discard it Protect buffers from excessive exposure to air Atmospheric carbon dioxide lowers the pH of alka line buffers Other trace gases commonly found in industrial environments for example ammonia and hydrogen chloride also affect the pH of buffers Molds from airborne spores grow readily in neutral a
173. measured at any temperature to the pH at a reference temperature The almost universal reference temperature is 25 C Different solutions require different solution temperature compensation Sub menus are a group of related menus collected under a single menu As used in the Model 3081 pH ORP manual standardization is the process of forcing the transmitter reading to match the reading of a second pH meter A plot of voltage against pH a straight line called an isotherm The slope of the isotherm is a function of temperature so a measured cell voltage corresponds to a different pH depending on temperature Temperature compensation is the process of selecting the correct isotherm The Model 3081 pH transmitter per forms automatic temperature compensation A warning advises the user that sensor performance is degrading Measurements might still be acceptable but the user should determine the cause of the problem and correct it as soon as possible Not acting when a warning limit is exceeded may ultimately lead to sensor failure 133 MODEL 3081 pH ORP SECTION 17 0 RETURN OF MATERIAL SECTION 17 0 RETURN OF MATERIAL 17 1 GENERAL To expedite the repair and return of instruments proper communication between the customer and the factory is important Call 1 949 757 8500 for a Return Materials Authorization RMA number 17 2 WARRANTY REPAIR The following is the procedure for returning instru ments still under warranty 1
174. measurement data are plot ted in terms of equation 4 The cell voltage E is repre sented by the dashed vertical line The contribution of each term in equation 4 to the voltage is also shown The liquid MODEL 3081 pH ORP junction potentials in the buffers are assumed to be equal and are exaggerated for clarity If the liquid junction potential in the sample differs from the buffers a measurement error results Figure 13 8 illus trates how the error comes about Assume the true pH of the sample is pH and the cell voltage is The point pH is shown on the graph If the liquid junction potential in the sample were equal to the value in the buffers the point would lie on the line However the liquid junction potential in the sample is greater so the point E lies above the cal ibration line Therefore when the cell voltage is converted to pH the result is greater than the true pH by the amount shown A typical mismatch between liquid junction potentials in buffer and sample is 2 3 mV which is equivalent to an error of about 50 02 pH units The mismatch produces a funda mental error in pH determinations using a cell with liquid junction 13 10 SENSOR DIAGNOSTICS Sensor diagnostics alert the user to problems with the sen sor or to actual sensor failures The two sensor diagnostics are reference impedance and glass impedance The major contributor to reference impedance is the resist ance across the liquid junct
175. menus are several sub menus For example under CALIBRATE the sub menus are CALIbrAtE Std stan dard and tEMP AdJ temperature adjust Under each sub menu are prompts For example under Std the prompts are Std xx xx and slope xx xx The DIAGNOSE menu lets the user view diagnostic messages Figure 5 4 shows the complete menu tree 5 4 DIAGNOSTIC MESSAGES pH Whenever a warning or fault limit has been exceeded the transmitter displays diagnostic messages to aid in trou bleshooting Diagnostic messages appear in the same area as the temperature output readings in the process display screen see Figure 5 1 The display alternates between the regular display and the diagnostic message Figure 5 4 shows the diagnostic fault messages for pH If more than one warning or fault message has been generated the messages appear alternately See Section 12 0 Troubleshooting for the meanings of the fault and warning messages CALIBRATE PROGRAM CALIbrAtE Std tEMP AdJ CAL bF1 Std 7 00 tEMP 25 0 InPut 58 9 GIMP 1000 10 bF 1 SLOPE 59 01 Em OutPut tEMP 5 bUFFEr ISOPOtntAL SIM OUtPUt bF 2 cp I I I 4 00 00 rOFFSt 060 On PH BAUtO On ICOEF 00 00 tESt 12 00
176. mitter The correct code must be entered before the transmitter can be programmed or calibrated To retrieve a lost security code see Section 5 7 To change the security code see Section 8 6 12 5 2 Transmitter Does Not Respond to Infrared Remote Controller IRC A Be sure the transmitter is receiving the signal 1 Clean the window in front of the IR detector The detector is a small rectangle just above the main display 2 Hold the IRC at least six feet from the transmitter and not more than 15 degrees from the center 3 Hold the IRC closer within two feet in case the batteries are getting weak B If step A fails to help check the IRC 1 If a second Model 3081 or Model 81 transmitter is available test the IRC on that transmitter If a spare transmitter is not available continue with step 2 2 The green LED located just above and between the RESET and HOLD buttons should light when a key is pressed A piece of black rubber film may be covering the LED Scrape the film away with your fingernail to expose the LED The two clear LEDs on the front end of the IRC never light They transmit the invisible IR signal 3 Ifthe green LED does not light the IRC is not working Go to step C C Take the IRC to a non hazardous area and replace the two 1 5 Vdc AAA batteries If the green LED lights but the transmitter still does not respond go to step D If neither the LED lights nor the transmitter responds replace the IRC PN 23572 01 D Re
177. mperature compensation to 25 C See Section 8 5 Refer to Figure 12 9 for connections to the sensor Remove the cover from the sensor Leave the sensor cable connector attached Remove the glass electrode cable from the BNC connection at the preamplifier Connect one end of a jumper wire to the solution ground pin and connect the other end to the reference electrode pin Both pins are underneath the preamplifier Leave the preamplifier installed on the pins Connect one end of a second jumper wire to the reference electrode pin Be sure the preamplifier remains connected to the pins Press DIAG on the IRC The InPut voltage in millivolts will appear in the temperature output area The main display will show pH COVER P N 23552 00 GLASS ELECTRODE CABLE SENSOR CABLE CONNECTOR PREAMPLIFIER N 23561 00 T C ELEMENT CONNECTIONS SOLUTION GROUND d IMPORTANT DO NOT CONNECT ANYTHING CONNECTION CUTSIDE OF PREAMP BNC CONNECTOR REFERENCE ELECTRODE JUMPER gt MILLIVOLT SOURCE NOTE REQUIRES SPECIAL JUMPERING TO SIMULATE pH THRU THE PREAMP DO NOT SHORT OUT BNC CONNECTOR DWG NO 40381 05 FIGURE 12 9 Simulate pH through Model 381 Sensor Preamplifier MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 10 Touch the other end of the second jumper to the center pin of the BNC connector on the preamplifier DO NOT LET THE WIRE TOUCH THE OUTSIDE OF THE BNC CONNECTOR 1
178. n Silver silver chloride internal reference Filling solution fixed chloride concentration and pH pH sensitive glass membrane Test Solution FIGURE 13 2 Measuring Electrode The essential element of the glass electrode is a pH sen sitive glass membrane An electrical potential develops at glass liquid interfaces The potential at the outside surface depends on the pH of the test solution The potential at the inside surface is fixed by the constant pH of the filling solution Overall the measuring electrode potential depends solely on the pH of the test solution SECTION 13 0 pH MEASUREMENTS The overall potential of the measuring electrode equals the potential of the internal reference electrode plus the poten tials at the glass membrane surfaces Because the poten tials inside the electrode are constant the overall electrode potential depends solely on the pH of the test solution The potential of the measuring electrode also depends on tem perature If the pH of the sample remains constant but the temperature changes the electrode potential will change Compensating for changes in glass electrode potential with temperature is an important part of the pH measurement Figure 13 3 shows a cross section through the pH glass pH sensitive glasses absorb water Although the water does not penetrate more than about 50 nanometers 5 x 10 8 m into the glass the hydrated layer must be present for the glass to respond to p
179. n error The more variable the temperature and the further the pH from 7 the greater the error Troubleshooting Flowchart tEMP HI and tEMP LO A Check wiring jumper settings and software settings 1 Check the wiring between the sensor and the transmitter Refer to the appropriate wiring diagram in Section 3 0 Pay particular attention to TB 3 RTD RTN TB 4 RTD SN and TB 5 RTD RTN NOTE TB 3 means terminal 3 on the terminal board 2 Be sure the position of the RTD jumper on the analog board matches the type of RTD in the sensor See Section 2 2 3 Be sure the software settings in Section 8 5 match the type of RTD in the sensor If the diagnostic message disappears the sensor is in good condition If the message persists go to step B 95 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING B Check the sensor 96 Refer to the wiring diagrams in Section 3 0 to identify the RTD leads Disconnect the RTD leads and measure the resistances shown in Figure 12 3 The measured resistance should agree with the value in Table 12 1 to within about 196 If the measured resistance is appreciably different between 1 and 596 from the value shown the discrepancy can be calibrated out See Section 8 5 Compare resistance between these wires to the values in Table 12 3 p Resistance between these wires RTD sense should be less than 2 ohms FIGURE 12 3 Three wire RTD Consult the table for resistance temperature data
180. n line about the point pH 7 A until the slope equals to 273 15 The microprocessor then uses the new isotherm to convert voltage to pH The point pH 7 A is called the isopotential pH As Figure 13 7 shows the isopotential pH is the pH at which the cell voltage does not change when the temperature changes 118 SECTION 13 0 pH MEASUREMENTS The microprocessor makes assumptions when the meas urement and calibration temperatures are different It assumes the actual measurement cell isotherms rotate about the point pH 7 A The assumption may not be cor rect so the measurement will be in error The size of the error depends on two things the difference between the isopotential pH of the measurement cell and pH 7 and the difference between the calibration and measurement tem peratures For a 10 C temperature difference and a differ ence in isopotential pH of 2 the error is about 0 07 pH units The factors that cause the isopotential pH of a real cell to differ from 7 are beyond the scope of this discussion and to a great extent are out of the control of the user as well Most pH cells do not have an isopotential pH point Instead the cell isopotential pH changes with temperature and the cell isotherms rotate about a general area Measuring the isopotential pH requires great care and patience One way to reduce the error caused by disagreement between the sensor and meter isopotential pH is to cali brate the sensor at
181. nal is correct and only the display is not working replace the display board PN 23652 01 If there is no response to pH changes replace the electronic board stack PN 23574 02 12 5 12 Display Segments Missing Replace the display board PN 23652 01 106 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 5 13 Transmitter Locks Up A Turn the dc power off then turn it back on B If the problem persists replace the electronic board stack 23574 02 12 5 14 Transmitter Periodically Restarts Itself A The problem is usually related to improperly wired RTD input terminals 1 The RTD return wire must be connected to TB 3 The RTD sense wire must be connected to TB 4 and the RTD in wire must be connected to TB 5 See the wiring diagrams in Section 3 0 If the pH sensor does not have an RTD connect a jumper wire across the terminals TB 3 and TB 4 and a second jumper across TB 4 and TB 5 2 Ifthe RTD connections have been jumpered as described in step B automatic temperature compensation must be turned off and the transmitter operated in manual temperature mode See Section 8 5 for the procedure B If RTD wiring is correct and problems still persist 1 Monitor the dc power supply Be sure the power is not intermittent and the correct voltage is present See Section 2 5 2 Try connecting the transmitter to a different power supply 12 6 SYSTEMATIC TROUBLESHOOTING This section contains troubleshooting flow charts for u
182. nce also occurs if the sensor is not submerged in the process liquid or if inappropriate limits have been entered into the transmitter If the measurement system was previously commissioned and operating correctly rEF FAIL likely means a real problem exists However if the system is being started up or if the advanced diagnostic feature is being used for the first time rEFFAIL could be caused by a miswired sensor or by programmed limits that are not correct for the sensor NOTE rEF FAIL is a sensor diagnostic message All sensor diagnostic mes sages are optional They can be turned off To disable sensor diagnostic messages refer to Section 8 4 3 93 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING Troubleshooting Flowchart rEF FAIL A Be sure the sensor is completely immersed in the process liquid is the diagnostic message disappears the sensor is in good condition If the diagnostic message remains go to step B B Check that the sensor is properly wired to the transmitter See the appropriate wiring diagram in Section 3 0 Be sure the reference in wire is attached to TB 7 and the solution ground wire is attached to TB 8 NOTE TB 8 means terminal 8 on the terminal board If correcting wiring problems makes the diagnostic message disappear the sensor is in good condition If wiring is correct and the message still remains go to step C C Measure and make a note of the reference impedance rIMP See Section 12 7 If the re
183. nd calibration procedures In calibrating and setting up instruments for shipping there is no step in any proce dure to enter a date MODEL 3081 pH ORP 1 3 SPECIFICATIONS GENERAL FOR MODEL 3081 pH ORP Case Cast aluminum containing less than 8 magnesium NEMA 4X IP65 NEMA 7 explosion proof Epoxy polyester paint Neoprene O ring seals Dimensions 6 3 in x 6 9 in x 6 4 in 160 mm x 175 mm x 161 mm diameter 6 1 in 155 mm Conduit Openings 3 4 in FNPT Reference Impedance Transmitter accepts high impedance i e glass reference electrodes as well as low impedance i e silver silver chloride reference electrodes Output Two wire 4 20 mA output with superimposed HART digital signal Output can be programmed to go to any value between 3 8 and 22 0 mA to indicate a fault or hold condition Response Time Display reaches 95 of final reading within 10 seconds Temperature Sensors The following RTDs can be used with the Model 3081 pH ORP transmitter 3 and 4 wire Pt 100 RTDs 3 and 4 wire Pt 1000 RTDs 3000 ohm Balco RTD Transmitter can also be used with two wire RTDs Temperature Range 5 F to 248 F 15 C 120 Local Display Two line LCD first line shows process vari able pH or ORP second line shows temperature and output signal When triggered fault and warning mes sages alternate with temperature and output readings Process variable 7 segment LCD 0 8 in 20 mm high Temperature output 7 segm
184. nd slightly acidic buffers Mold growth can substantially alter the pH of a buffer Rinse the sensor with deionized water before placing it in a buffer Remove excess water from the sensor by gently daubing it with a clean tissue Do not wipe the sensor Wiping may generate a static charge leading to noisy readings The static charge may take hours to dissipate A few drops of deionized water carried with the sensor into the buffer will not appreciably alter the pH MODEL 3081 pH ORP CALIBRATE CALIbrAtE EXIT NEXT ENTER CALIBRATE CAL bF 1 EXIT NEXT CALIBRATE ENTER SECTION 7 0 CALIBRATION OF pH MEASUREMENTS NOTE A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each nearby transmitter See Section 5 7 Security NOTE During calibration the sensor may be exposed to solutions having pH outside the normal range of the process To prevent false alarms and possible unde sired operation of chemical dosing pumps place the analyzer in hold during calibration See Section 7 3 Using the Hold Function for details 7 5 4 Procedure 10 11 12 13 Refer to Section 8 7 Buffer Calibration Parameters Verify that auto calibration is activated Identify the buffers being used and set the stability limits Enter the CALIBRATE menu by pressing CAL on the IRC The CALIbrAtE sub menu appears
185. nde pendent of ORP and the liquid junction potential is small the measured cell voltage is controlled by the ORP of the sample Stated another way the cell voltage is the ORP of the sample relative to the reference electrode FIGURE 14 5 Electrode Potential 14 6 ORP CONCENTRATION AND pH ORP depends on the relative concentration of oxidized and reduced substances in the sample and on the pH of the sample An understanding of how concentration and pH influence ORP is necessary for the correct interpretation of ORP readings The drawing shows an iron II and iron III ion at the sur face of a platinum electrode Iron can take an electron from the platinum and be reduced and iron 11 can place an electron on the metal and be oxidized The electrode potential is the tendency of the half reaction shown in the figure to occur spontaneously Because the voltmeter used to measure ORP draws almost no current there is no change in the concentration of iron Il and iron III at the electrode 122 MODEL 3081 pH ORP is described by the following equation called the Nernst equation _ 500 1987 t 273 15 Fe E n Fe 3 2 In the Nernst equation E is the electrode potential and E is the standard electrode potential both in millivolts t is temperature in C n is the number of electrons transferred n 1 in the present case and Fe and Fe 3 are the concentrations of iron Il and iron III
186. ner The detector for the infrared remote controller is located behind the window at the top of the transmitter face The window in front of the detec tor must be kept clean Most components of the transmitter are replaceable Refer to Figure 11 1 and Table 11 1 for parts and part numbers PN 33337 02 5 PN 33360 00 7 33362 00 PN 33343 00 RIBBON CABLE 4 PN 33342 00 6 23593 01 FIGURE 11 1 Exploded View of Model 3081 pH ORP Transmitter Three screws part 13 in the drawing hold the three circuit boards in place Removing the screws allows the display board part 2 and the CPU board part 3 to be easily removed A ribbon cable connects the boards The cable plugs into the CPU board and is permanently attached to the display board A 16 pin and socket connector holds the CPU and analog part 4 boards together Five screws hold the terminal block part 5 to the center housing part 7 and the 16 pins on the terminal block mate with 16 sockets on the back side of the analog board Use caution when separat ing the terminal block from the analog board The pin and socket connection is tight MODEL 3081 pH ORP SECTION 11 0 MAINTENANCE TABLE 11 1 Replacement Parts for Model 3081 pH ORP Transmitter Location in Shipping Figure 11 1 Description Weight 23574 02 PCB stack consisting of the CPU part 3 and analog part 4 boards 1 16 0 5 kg display board is not included CPU and analog boards are factory calib
187. now the electrode slope To display the slope press CAL on the IRC The CALIbrAtE sub menu will appear Press NEXT The Std sub menu appears Press ENTER The Std prompt appears Press ENTER again and SLOPE xx xx will appear in the display The four digit number is the electrode slope For a good sensor the slope is between 50 and 60 51 MODEL 3081 pH ORP IMPORTANT 52 7 6 SECTION 7 0 CALIBRATION OF pH MEASUREMENTS MANUAL CALIBRATION 7 6 1 Purpose New sensors must be calibrated before use Regular recalibration is also necessary Manual calibration is an alternative to auto calibration Because auto calibration eliminates many common calibration errors it is strongly recommended In auto calibration the transmitter recognizes the buffer and uses the temperature corrected pH value in the calibration The transmitter also measures noise and drift and does not accept cali bration data until readings meet programmed limits In manual calibration however the user must judge when readings are stable look up the buffer value at the calibration temperature and key in the value Manual calibration is necessary if non standard buffers are used for calibration Manual calibration is also useful in troubleshooting Because temperature readings from the pH sensor are not available during calibration a reliable thermometer is required to complete the procedure 7 6 2 Use of calibration standards buffers 1 2 A pH me
188. nsmitter is in hold The range is 3 80 to 22 00 mA Entering 00 00 causes the transmitter to hold the output at the value it was when placed in hold The hold setting overrides the fault setting Press ENTER to save The screen displays the FAULt prompt Use the editing keys to change the display to the output desired when the transmitter detects a fault The range is 3 80 to 22 00 mA Entering 00 00 causes the transmitter to hold the output at the value it was when the fault occurred Press ENTER to save The screen displays the dPn prompt Use the editing keys to change the display to the desired output dampening The range is 0 to 255 Press ENTER to save Press EXIT to return to the process display MODEL 3081 pH ORP SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS 10 4 DIAGNOSTIC PARAMETERS 10 4 1 Purpose This section describes how to do the following 1 change the standardization reference offset 2 enable and disable sensor diagnostics 3 enable and disable glass impedance temperature compensation for a glass reference electrode 4 setthe high and low warning and failure limits for a glass reference electrode 10 4 2 Definitions 1 STANDARDIZATION OFFSET REFERENCE OFFSET During calibration the transmitter reading is made to match the ORP of a standard solution If the difference between the transmitter reading and the desired value exceeds the programmed limit the trans mitter will not accept the new reading The defa
189. nt takes only seconds REMOTE COMMUNICATIONS Remote communica tions with the Model 3081 pH ORP transmitter is easy The hand held push button infrared remote controller works from as far away as six feet The transmitter also belongs to the Rosemount SMART FAMILY so it works with the Model 275 HART hand held communi cator or with any host that supports the HART protocol DISPLAY The 0 8 inch high LCD main display means pH and ORP values are easy to read even at a distance Secondary variables temperature and current output appear in a 0 3 inch high display MENUS Menu formats for calibration and programming are simple and intuitive Prompts guide the user through the basic procedures Diagnostic and error messages appear in plain language There are no annoying codes to look up MODEL 3081 pH ORP CALIBRATION Two point temperature corrected buffer calibration is standard To reduce errors caused by impatient operators the Model 3081 pH ORP transmitter does not accept calibration data until programmed stabil ity limits have been met If data are not acceptable the transmitter displays an error message and does not update the calibration The transmitter recognizes every buffer scale in common use in the world Manual two point and one point calibration are also available AUTOMATIC TEMPERATURE COMPENSATION Temperature compensation is completely automatic The Model 3081 pH ORP transmitter is compatible with two thre
190. o not let the weight of the sensor rest on the glass bulb Stir continuously Allow at least 20 minutes for the standard thermometer sensor and water to reach constant temperature Enter the CALIBRATE menu by pressing CAL on the IRC The CALIbrAtE sub menu appears pictured above left At the CALIbrAtE sub menu press NEXT twice The tEMP AdJ sub menu appears Press ENTER to display the temperature editing prompt Compare the temperature displayed by the transmitter with the temperature measured with the reference thermometer If the readings are different use the editing keys to change the flashing display to the value determined with the reference thermometer The reading cannot be changed by more than 15 C Press ENTER The value will be saved and the display will return to the tEMP AdJ sub menu To leave the CALIBRATE menu press EXIT Check linearity by measuring the temperature of water 10 to 15 C cooler and 10 to 15 C warmer than the water used for calibration Because of the time required for the temperature element in the sensor to reach constant temperature a well insulated container or better a constant temperature bath is required for this step 49 MODEL 3081 pH ORP IMPORTANT 50 SECTION 7 0 CALIBRATION OF pH MEASUREMENTS 7 5 AUTO CALIBRATION 7 5 1 Purpose New sensors must be calibrated before use Regular recalibration is also necessary The use of auto calibration instead of manual calibrat
191. ocedures If the sensor is not rebuildable see Section 11 3 4 for a method of rejuvenating the reference junction If the sensor is rebuildable replenish the reference electrolyte and replace the liquid junction gv Rm Replace the sensor A clean pH sensor should not drift in buffer 103 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 5 5 pH Reading in Buffer Drifts During Manual Calibration A Allow adequate time for the temperature of the sensor to reach the temperature of the buffer If the sensor was in a process substantially hotter or colder than the buffer allow at least 20 minutes for readings in the buffer to stabilize Alternatively place the sensor in a container of water at ambient temperature for 20 minutes before starting the calibration B Be sure to swirl sensor after placing it in each new buffer solution Finally check the sensor Verify that wiring is correct Also the sensor may be dirty or aged or the reference junction may be depleted 1 Check that the sensor is properly wired to the transmitter See Section 3 0 Pay particular attention to terminals TB 10 mV in TB 7 reference and TB 8 solution ground See Section 11 3 for cleaning procedures If the sensor is not rebuildable see Section 11 3 4 for a method of rejuvenating the reference junction If the sensor is rebuildable replenish the reference electrolyte and replace the liquid junction CY Replace the sensor A c
192. of sulfur dioxide is present the chromium cou ple no longer determines ORP Instead ORP is con trolled by the sulfur dioxide sulfate couple When sulfur dioxide reacts with chromium VI it is converted to sul fate Figure 14 6 shows how ORP and the concentra tion of chromium VI change as sulfur dioxide is added Because the change in ORP at the endpoint is large monitoring ORP is an efficient way of tracking the process SECTION 14 0 ORP MEASUREMENTS N Cr VI ORP mV E 3 o lt o Sulfur dioxide added FIGURE 14 6 ORP Measurement Interpretation ORP measures activity not concentration Activity accounts for the way in which other ions in solution influence the behavior of the redox couple being meas ured To be strictly correct ORP is controlled by the the ratio of activities not concentrations The dependence of ORP on activity has an important consequence Suppose a salt like sodium sulfate is added to a solu tion containing a redox couple for example iron Il and iron IIl The sodium sulfate does not change the con centration of either ion But the ORP of the solution does change because the salt alters the ratio of the activity of the ions pH can have a profound influence on ORP Referring to the earlier example where ORP was used to monitor the conversion of chromium VI to chromium III The reaction is generally carried out at about pH 2 Because the concentration
193. olutions come into contact The magnitude of the potential depends on the difference between the mobility of the ions Although liquid junction potentials cannot be elim inated they can be made small and relatively constant A small liquid junction potential exists when the ions present in greatest concentration have equal or almost equal mobilities The customary way of reducing junction poten Figure 14 5 shows a platinum ORP electrode in contact with a solution of iron and iron III As discussed earli er iron 11 and iron are a redox couple They relat ed by the following half reaction Fe 1 If a redox couple is present a stable electrical potential eventually develops at the interface between the platinum e tials is to fill the reference electrode with concentrated potassium chloride solution The high concentration ensures that potassium chloride is the major contributor to the junction potential and the nearly equal mobilities of potassium and chloride ions makes the potential small electrode and the sample The magnitude of the potential Platinum electrode Solution 14 5 RELATING CELL VOLTAGE TO ORP The measured cell voltage E T the notation emphasizes the temperature dependence is the algebraic sum of the measuring platinum electrode potential the reference electrode potential and the liquid junction potential Because the potential of the reference electrode is i
194. om Rosemount Measurement at 800 999 9307 B Be sure the HART load and voltage requirements are met 1 HART communications requires a minimum 250 ohm load in the current loop 2 Install a 250 500 ohm resistor in series with the current loop Check the actual resistor value with an ohmmeter 3 For HART communications the power supply voltage must be at least 18 Vdc See Section 2 5 C Be sure the HART Communicator is properly connected 1 The Communicator leads must be connected across the load 2 The Communicator can be connected across the power terminals TB 15 and TB 16 D Verify that the Model 275 is working correctly by testing it on another HART Smart device 1 If the Communicator is working the transmitter electronics may have failed Call Rosemount Analytical for assistance 2 Ifthe Communicator seems to be malfunctioning call Rosemount Measurement at 800 999 9307 for assistance 12 5 11 No Display A Be sure power requirements are being met 1 The positive voltage lead must be connected to TB 16 2 Check dc voltage requirements and load restrictions Refer to Section 2 5 B Check for bad connections between the circuit boards Refer to Section 2 2 Be sure the ribbon cable between the display and CPU boards is firmly seated in the socket on the CPU board Be sure the socket connection between the CPU and analog boards is firm C If power is correct and connections are good check the 4 20 mA output signal i the sig
195. on reinstall the sensor in the process stream Wait until readings have stabilized before deactivating Hold To activate or deactivate Hold do the following 1 Press HOLD on the IRC 2 The prompt appears in the display Press or to toggle the Hold function between On and OFF 3 Press ENTER to save 48 MODEL 3081 pH ORP CALIBRATE CALIbrAtE EXIT NEXT ENTER NEXT ENTER SECTION 7 0 CALIBRATION OF pH MEASUREMENTS 7 4 TEMPERATURE CALIBRATION 7 4 1 Purpose 1 As discussed in Section 13 6 Glass Electrode Slope measuring tempera ture is an important part of measuring pH The accuracy of a new sensor and transmitter loop is about 1 C which is adequate for most applications A new sensor seldom requires temperature calibration 2 Calibrate the sensor transmitter loop if 1 C accuracy is NOT acceptable or b the temperature measurement is suspected of being in error NOTE A transmitter adjacent to the one being calibrated may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each nearby transmitter See Section 5 7 Security 7 4 2 Procedure 1 Place the pH sensor and a calibrated reference thermometer in an insulated container of water at ambient temperature Be sure the temperature ele ment in the sensor is completely submerged by keeping the sensor tip at least three inches below the water level D
196. or and measurement problems in the United States call Rosemount Analytical Uniloc Division at 800 854 8527 outside the United States call the nearest Fisher Rosemount office See the back page of the manual 12 9 2 Return of Materials If itis necessary to return the transmitter to the factory for repairs in the United States call Rosemount Analytical Uniloc Division at 800 854 8527 outside the United States call the nearest Fisher Rosemount office See the back page of the manual Always call before returning material Do not send anything without obtaining a Return Material Authorization RMA number 113 MODEL 3081 pH ORP SECTION 13 0 pH MEASUREMENTS SECTION 13 0 pH MEASUREMENTS 13 1 General 13 2 Measuring Electrode 13 3 Reference Electrode 13 4 Liquid Junction Potential 13 5 Converting Voltage to pH 13 6 Glass Electrode Slope 13 7 Buffers and Calibration 13 8 Isopotential pH 13 9 Junction Potential Mismatch 13 10 Sensor Diagnostics 13 11 Shields Insulation and Preamplifiers fpe TECHNICAL STUFF 13 1 GENERAL In nearly every industrial and scientific application pH is determined by measuring the voltage of an electrochemical cell Figure 13 1 shows a simplified diagram of a pH cell The cell consists of a measuring electrode a reference electrode a temperature sensing element and the liquid being measured The voltage of the cell is directly proportional to the pH of the liquid The pH met
197. or the first time GLASSFAIL could be caused by a miswired sensor or by programmed limits that are not correct for the sensor NOTE GLASSFAIL is a sensor diagnostic message Sensor diagnostic mes sages are optional They can be turned off To disable sensor diagnostic messages refer to Section 8 4 3 Troubleshooting Flowchart GLASSFAIL A Be sure the sensor is completely immersed in the process liquid the diagnostic message disappears the sensor is in good condition If the diagnostic message remains go to step B B Measure the glass impedance See Section 12 7 for the procedure Note the reading If the glass impedance is low 40 megohms 1 Be sure the position of switch S 1 on the analog board matches the location of the preamplifier See Section 2 2 If switch S 1 was correct go to step 2 If moving the switch to the correct position makes the diagnostic message disappear the sensor is in good con dition If after moving the switch the glass impedance is still low go to step 2 2 Calibrate the sensor Use the autocalibration procedure in Section 7 5 If the sensor calibrates properly a The sensor is in good condition but the Glass Fail Low GFL limit is set too high b Lower the GFL limit to about 10 megohms below the glass impedance value GIMP measured in step B c Ifthe Glass Warning Low GWL message was also flashing lower the limit from its former value by the same amount GFL was lowered from its fo
198. ore electrostatic charges which accumulate on the wire from environmental influences cannot readily drain away Buildup of charge results in degraded noisy readings Shielding the wire with metal braid connected to ground at the instrument is one way to improve the signal It is also helpful to keep the sen sor cable as far away as possible from AC power cables The high input impedance of the pH meter requires that the lead insulation and the insulation between the meter inputs be of high quality To provide further protection from envi ronmental interference the entire sensor cable can be enclosed in conduit To avoid the need for expensive cable and cable installa tions a preamplifier built into the sensor or installed in a junction box near the sensor can be used The preamplifi er converts the high impedance signal into a low imped ance signal that can be sent as far as 200 feet without spe cial cable E E pH t Eij buffer 2 pHs Es a sample E pH t pH error caused by liquid junction potential mismatch FIGURE 13 8 Liquid Junction Potential Mismatch The dashed vertical lines are the measured cell voltages for the buffers and the sample The contribution from each term in equation 4 is shown The buffers are are assumed to have identical liquid junction potentials Because most buffers are equitransferant i e the mobilities of the ions making up the buffer are nearly equal assuming
199. oride wire Potassium chloride filling solution 8 Salt bridge FIGURE 14 3 Reference Electrode The fixed concentration of chloride inside the elec trode keeps the potential constant A porous plug salt bridge at the bottom of the electrode permits electrical contact between the reference electrode and the test solution 121 SECTION 14 0 ORP MEASUREMENTS MODEL 3081 pH ORP FIGURE 14 4 The Origin of Liquid Junction Potentials The figure shows a thin section through a pore in the junction plug The junction separates a solution of potassium chloride on the left from a solution of hydrochloric acid on the right The solutions have equal molar concentration Driven by con centration differences hydrogen ions and potassium ions diffuse in the directions shown The length of each arrow indicates relative rates Because hydrogen ions move faster than potassium ions positive charge builds up on the left side of the sec tion and negative charge builds up on the right side The ever increasing positive charge repels hydrogen and potassium ions The ever increasing negative charge attracts the ions Therefore the migration rate of hydrogen decreases and the migration rate of potassium increases Eventually the rates become equal Because the chloride concentrations are the same chloride does not influence the charge separation or the liquid junction potential Liquid junction potentials exist whenever dissimilar elec trolyte s
200. ose scale or debris Use a stream of water from a wash bottle to rinse away solids from the tip of the sensor If water does not work gently wipe the glass bulb and liquid junction with a Soft cloth tissue cotton tipped swab or a soft bristle brush Oil and grease Wash the glass bulb with mild detergent solution and rinse thoroughly with water Hard scale carbonate If wiping the sensor tip with a tissue or cotton swab does not remove the scale soak the sulfate scales and glass bulb ONLY in a solution of 5 hydrochloric acid To prepare the acid solution add corrosion products 15 mL of concentrated hydrochloric acid to 85 mL of water with constant stirring Keep the acid away from the liquid junction and from any stainless steel portions of the sensor Rinse the sensor thoroughly with deionized water Some scales for example calcium sulfate cannot be removed easily with acid Soaking the glass bulb in a 2 solution of disodium EDTA may be helpful MODEL 3081 pH ORP SECTION 11 0 MAINTENANCE When using acid or alkaline solvents be careful to keep the solvent away from the liquid junction If the cleaning sol vent contacts the junction hydrogen ions acid solvent or hydroxide ions alkaline solvent will diffuse into the junc tion Because hydrogen and hydroxide ions have much greater mobility than other ions they produce a large junction potential When the electrode goes back in service the hydrogen or hydroxide ions slowly diffus
201. paration increases electro static forces cause the faster moving ions to slow down and the slower moving ions to speed up Eventually the migra tion rates become equal and the system reaches equilibri um The amount of charge separation at equilibrium deter mines the liquid junction potential Liquid junction potentials exist whenever dissimilar elec trolyte solutions come into contact The magnitude of the potential depends on the difference between the mobility of the ions Although liquid junction potentials cannot be elim inated they can be made small and relatively constant A small liquid junction potential exists when the ions present in greatest concentration have equal or almost equal mobilities The customary way of reducing junction poten tials is to fill the reference electrode with concentrated potassium chloride solution The high concentration ensures that potassium chloride is the major contributor to the junction potential and the nearly equal mobilities of potassium and chloride ions makes the potential small 13 5 CONVERTING VOLTAGE TO pH Equation 1 summarizes the relationship between meas ured cell voltage in mV pH and temperature in Kelvin E T 0 1984 T pH 1 The cell voltage E T the notation emphasizes the dependence of cell voltage on temperature is the sum of five electrical potentials Four are independent of the pH of the test solution and are combined in the first term
202. pick up signals from the IRC To avoid accidentally chang ing settings use a different security code for each nearby transmitter See Section 5 7 Security and Section 10 6 Display Units for details 9 3 USING THE HOLD FUNCTION During calibration the sensor may be exposed to solutions having an ORP outside the normal range of the process To prevent false alarms and possible undesired operation of chemical dosing pumps place the transmit ter in hold during calibration Activating HOLD keeps the transmitter output at the last value or sends the output to a previously determined value See Section 10 3 Output Ranging for details After calibration reinstall the sensor in the process stream Wait until readings have stabilized before deactivating Hold To activate or deactivate Hold do the following 1 Press HOLD on the IRC 2 The HoLd prompt appears in the display Press or to toggle the Hold function between On and OFF 3 Press ENTER to save the setting 72 MODEL 3081 pH ORP IMPORTANT CALIBRATE Std EXIT NEXT ENTER NEXT ENTER 125 0 ENTER SECTION 9 0 CALIBRATION OF ORP MEASUREMENTS 9 4 TEMPERATURE CALIBRATION 9 4 1 Purpose 1 As discussed in Section 14 6 ORP Concentration and pH ORP is a function of temperature The accuracy of a new sensor transmitter loop is about 1 which is adequate for most applications A new sensor sel dom requires temperature calibration
203. place the transmitter display board PN 23652 00 12 5 3 SLOPE Err LO or SLOPE Err HI Appear After Calibration Attempt Refer to Section 12 4 9 and Section 12 4 10 for assistance in solving calibration slope problems 12 5 4 bF1 or bF2 Continuously Flashes During Auto Calibration During autocalibration bF1 or bF2 flashes until the pH reading of the sensor in buffer is stable A Checkthe stability limits set in Section 8 7 If the stabilization range prompt PH is set too narrow or the stabilization time prompt tIME is set too long the transmitter will not accept buffer readings A good choice for PH is 0 02 and a good choice for is 10 20 seconds B Allow adequate time for the temperature of the sensor to reach the temperature of the buffer If the sensor was in a process substantially hotter or colder than the buffer allow at least 20 minutes for readings in the buffer to stabilize Alternatively place the sensor in a container of water at ambient temperature for 20 minutes before starting the calibration C Be sure to swirl sensor after placing it in each new buffer solution D Finally check the sensor Verify that wiring is correct Also the sensor may be dirty or aged or the reference junction may be depleted 1 Check that the sensor is properly wired to the transmitter See Section 3 0 Pay particular attention to terminals TB 10 mV in TB 7 reference and TB 8 solution ground See Section 11 3 for cleaning pr
204. ponent to the analog signal HART permits digital communication while retaining the analog signal for process control The HART protocol originally developed by Fisher Rosemount is now overseen by the independent HART Communication Foundation The Foundation ensures that all HART devices can communicate with one another For more information about HART communications call the HART Communication Foundation at 512 794 0369 The internet address is http www hartcomm org 15 2 HART INTERFACE DEVICES HART communicators allow the user to view measurement data pH ORP and temperature program the transmit ter and download information from the transmitter for transfer to a computer for analysis Downloaded information can also be sent to another HART transmitter Either a hand held communicator such as the Rosemount Model 275 or a computer can be used HART interface devices operate from any wiring termination point in the 4 20 mA loop A minimum load of 250 ohms must be present between the transmitter and the power supply See Figure 15 1 4 20 mA Digital Model 3081 pH Smart Transmitter Hand Held Communicator Configurator Viri Hurt E Computer FIGURE 15 1 HART Communicators Both the Rosemount Model 275 and a computer can be used to communicate with a HART transmitter The 250 ohm load minimum must be present between the transmit ter and the power supply 126 MODEL 3081 pH ORP SECTION 15 0 THEORY REM
205. r Calibration involves the use of solutions having exactly know pH called calibration buffers or simply buffers Assigning a pH value to a buffer is not a simple process The laboratory work is demanding and extensive theoretical work is needed to support certain assumptions that must be made Normally establishing pH scales is a task best left to national stan dards laboratories pH scales developed by the United States National Institute of Standards and Technology NIST the British Standards Institute BSI the Japan Standards Institute JSI and the German Deutsche Institute fur Normung DIN are in common use Although there are some minor differences for practical purposes the scales are identical Commercial buffers are usually trace able to a recognized standard scale Generally commercial buffers are less accurate than standard buffers Typical accuracy is 0 01 pH units Commercial buffers sometimes called technical buffers do have greater buffer capacity They are less susceptible to accidental contamination and dilution than standard buffers Figure 13 7 shows graphically what happens during cali bration The example assumes calibration is being done at 117 MODEL 3081 pH ORP pH 7 00 and pH 10 00 When the electrodes are placed in pH 7 buffer the cell voltage is V7 and when the electrodes are placed in pH 10 buffer the cell voltage is Note that V is not 0 mV as would be expected an ideal sensor but
206. r is being used disconnect the wires at the input side of the junction box 2 Tape back the ends of the disconnected wires including all shield and drain wires to keep them from making accidental connections with other wires terminals or the transmitter case 3 Connect a jumper wire between TB 3 RTD RTN and TB 4 RTD SNS Connect a second jumper wire between TB 7 REF IN and TB 8 SOL GND 4 Place the sensor back in the process liquid If diagnostic messages such as GLASSFAIL or REF WArn appear turn off the sensor diagnostics See Section 8 4 If the symptoms disappear interference was coming into the transmitter along one of the sensor wires The measurement system can be operated permanently with the simplified wiring If symptoms still persist go to step D D Check for extra ground connections or induced noise 1 The electrode system is connected to earth ground through the process If other ground connections exist there are multiple paths and ground loops are present Noise enters the measurement either by a direct connection usually between the cable and grounded metal or by an indirect connection usually EMI RFI picked up by the cable 2 Ifthe sensor cable is run inside conduit there may be a short between the cable and the conduit Re run the cable outside the conduit If symptoms disappear then a short exists between the cable and the conduit Likely a shield is exposed and is touching the conduit Repair the ca
207. rated as a unit and cannot be ordered separately 23652 01 LCD display PCB 1 16 0 5 kg 33337 02 Terminal block 1 16 0 5 kg 23593 01 Enclosure cover front with glass window 3 Ib 1 5 kg 33360 00 Enclosure center housing 4 10 1 5 kg 33362 00 Enclosure cover rear 3 Ib 1 0 kg 6560135 Desiccant in bag one each 1 16 0 5 kg 9550187 O ring 2 252 one and rear covers each require an O ring 1 16 0 5 kg Screw 8 32 x 0 5 inch for attaching terminal block to center housing note Screw 8 32 x 1 75 inch for attaching circuit board stack to center housing 33342 00 11505 kg 33343 00 Locking bracket nut 1 16 0 5 kg note Screw 10 24 x 0 38 inch for attaching cover lock and locking bracket nut to center housing NOTE For information only Screws cannot be purchased from Rosemount Analytical Weights are rounded up to the nearest whole pound or 0 5 kg 11 3 pH SENSOR MAINTENANCE 11 3 1 Frequency of Cleaning The frequency at which a sensor should be inspected and cleaned can be determined only by experience If the process liquid coats or fouls the sensor frequent cleaning may be necessary If the process does not contain a high level of sus pended solids the need for regular cleaning will be less Often an increase in glass impedance indicates the electrode is becoming fouled and needs cleaning Refer to Section 8 4 for a description of the glass impedance diagnostic 11 3 2 Cleaning Procedures PROBLEM CLEANING SUGGESTIONS Lo
208. reater the error when the calibration and measurement tem peratures are different A plot of cell voltage against pH is a straight line The line is called an isotherm When temperature changes the slope of the isotherm changes Therefore the pH to which a given cell voltage corresponds depends on temperature Meter isotherms intersect at the meter isopotential point Isotherms for pH measurement cells rarely intersect at a single point but they usually cross in a fairly small area Signal carrying wires are conveniently joined together in a junction box Usually the box contains two terminal strips connected internally point to point The wires in one cable are terminated on one strip and the wires in the other cable are ter minated on the second strip The point to point connection between the terminal strips produces a point to point connection between the wires A liquid junction potential exists when two dissimilar electrolyte solutions come into contact but are not allowed to mix The potential arises from the different mobilities of the ions in the contacting solutions Generally the solution of great est concentration has the greatest influence on the size of the liquid junction potential Although liquid junction potentials cannot be eliminated they can be made small and relatively constant if the concentrated solution contains ions of equal or nearly equal mobilities A measuring electrode is an electrode for which the potential is
209. ress ENTER The first sub menu will appear For more information see Section 5 7 Security A transmitter adjacent to the one being programmed may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each nearby transmitter See Section 5 7 Security and Section 10 6 Display Units for details 75 SECTION 10 0 PROGRAMMING FOR ORP MEASUREMENTS MODEL 3081 pH ORP TABLE 10 1 ORP Settings Llst PROGRAM LEVEL A Output Range Section 10 3 4 mA Output 20 mA Output Hold Dampening Fault Current Output Setting Diagnostic Section 10 4 Reference Cell Offset Standardize error Diagnostics Function Glass Impedance Temperature Correction Reference Cell Impedance Type Reference Cell High Impedance Fault Reference Cell High Impedance Warning Reference Cell Low Impedance Warning Reference Cell Low Impedance Fault Temperature Section 10 5 Temperature Sensor Type D Display Section 10 6 1 Measurement type 2 Temperature Units 3 Output Units 4 Code E Output Simulation Section 10 7 1 Test 76 MNEMONIC OutPut HoLd dPn FAULt dIAGnOStIC rOFFSt dlAG IMPtC rEF rFH rWH rWL rFL tEMP tC dISPLAY tYPE tEMP OUtPUt COdE SIMOUtPUt tESt DISPLAY LIMITS 1400 to 1400 mV 1400 to 1400 mV 3 80 to 22 00 mA 0 to 255 seconds 3 80 to 22 00 mA 0 to 1000 mV On Off On Off LO HI 0 to 2000 me
210. ridge Shield 132 SECTION 16 0 GLOSSARY Although pH is often defined as the negative common logarithm of the hydrogen ion activity pH is best defined by describing how it is measured The measure ment requires three steps Assemble an electrochemical cell consisting of a glass electrode a reference electrode and the solution Calibrate the cell by measur ing the voltage of two standard buffer solutions Finally measure the cell voltage with sample present Because voltage is directly proportional to pH the pH of the sample can be calculated from the calibration data The operational definition places the pH of the sample on the pH scale defined by the buffers A platinum electrode is a noble metal electrode commonly used for measuring ORP The potential developed at the electrode is directly proportional to the ratio of the concentrations of oxidized and reduced substances present in the sample pH influences the ORP As the name implies platinum is the sensing element in a platinum RTD Platinum RTDs are usually identified in terms of their resistance at 0 C The resistance of a platinum RTD changes 0 39 per A preamplifier located in either the sensor or in a junction box close to the sen sor boosts the signal from the sensor before sending it to the analyzer Generally if the pH signal is to be sent more than about 15 feet it should be preamplified The process display of the Model 3081pH ORP transmitter continuous
211. rmer value If the sensor cannot be calibrated The pH sensitive glass membrane is likely cracked and the sensor must be replaced The crack in the glass may not be visible or may be difficult to see If the glass impedance is high 2800 megohms 1 Check that the sensor is correctly wired to the transmitter See the appropriate wiring diagram in Section 3 0 Pay particular attention to the following a For Rosemount Analytical PLUS and TUpH sensors with integral preamplifiers the blue solution ground wire must be attached to TB 8 SOL GND and the gray reference in wire must be attached to TB 7 REF IN NOTE TB 8 means terminal 8 on the terminal board 91 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING b Ifthe sensor was wired with the blue solution ground wire unattached and a jumper between terminals TB 8 and TB 7 remove the jumper and reattach the blue solution ground wire to TB 8 Keep the gray reference in wire attached to TB 7 c For Rosemount Analytical PLUS and TUpH sensors that do not have an integral preamplifier attach the blue solution ground wire to TB 8 or better leave the blue wire unattached and jumper TB 7 to TB 8 d Ifthe sensor does not have a blue solution ground wire jumper terminals TB 7 and TB 8 If the wiring was correct and the glass impedance is still high go on to step 2 If correcting wiring errors causes the diagnostic message to disappear the sensor is in good condition If aft
212. rmination of chlorine in water When water is disinfected by treatment with chlorine gas or sodium hypochlorite free chlorine forms Free chlorine is a mixture of hypochlorous acid and hypochlorite ions OCI The relative amount of hypochlorous acid and hypochlorite present depends on pH For disinfection control total free chlo rine the sum of hypochlorous acid and hypochlorite ion is important Equation 5 shows the half reaction for hypochlorous acid 5 The Nernst equation is 0 1987 t 273 15 CI zu 2 Noo Only the concentration of hypochlorous acid appears in the Nernst equation To use ORP to determine total free chlorine equation 6 must be rewritten in terms of 124 SECTION 14 0 ORP MEASUREMENTS free chlorine Although the details are beyond the scope of this discussion the result is shown in equation 7 K 0 1987 t 273 15 P 2 H 2 E E lo where K is the acid dissociation constant for hypochlor ous acid 2 3 x 10 8 and Ca is the total free chlorine concentration As equation 7 shows the measured ORP depends on the hydrogen ion concentration i e pH the chloride concentration the free chlorine con centration and temperature Therefore for ORP to be a reliable measurement of free chlorine pH chloride and temperature must be reasonably constant Assume the free chlorine level is 1 00 ppm and the chlori
213. ruction manual 4 20 mA Digital h 12 11 Model 3081 pH Smart Transmitter Hand Held Communicator Configurator Computer FIGURE 6 1 Connecting the HART Communicator 42 MODEL 3081 pH ORP SECTION 6 0 OPERATION WITH MODEL 275 6 3 Operation 6 3 1 Off line and On line Operation The Model 275 Communicator features off line and on line communications On line means the communicator is connected to the transmitter in the usual fashion While the communicator is on line the operator can view meas urement data change program settings and read diagnostic messages Off line means the communicator is not connected to the transmitter When the communicator is off line the operator can still program settings into the communicator Later after the communicator has been connected to a transmitter the operator can transfer the programmed settings to the transmitter Off line operation permits settings common to several transmitters to be easily stored in all of them 6 3 2 Menu Tree Figure 6 2 shows the menu tree for the Model 3081 pH transmitter Figure 6 3 shows the menu tree for the Model 3081 ORP transmitter 6 3 3 Fast Key Sequences Fast key sequences are a series of key presses that begin at the on line menu and lead directly to a given oper ation for example standardize Some useful sequences are the following Key Presses 5 Co 1 Calibrate with buffers 2 Standardize
214. s ORP 5 7 Security 5 1 DISPLAYS Figure 5 1 shows the process display screen and Figure 5 2 shows the program display screen pH or ORP ORP in mV d EET Transmitter output signal in mA or of full scale 9502 00 ma Temperature in C or F FIGURE 5 1 Process Display Screen The process display screen appears during normal operation Appears during HART and AMS pH or ORP ORP in mV operations Units of display Appears when a disabling condition has occurred see Section 8 3 2 Active menu CALIBRATE PROGRAM or DIAGNOSE Ar c n Appears when transmitter is in hold see Section 8 3 2 E Sub menus prompts and Available commands for sub diagnostic messages appear menu prompt or diagnostic here FIGURE 5 2 Program Display Screen The program display screen appears when calibrating programming or reading diagnostic messages MODEL 3081 pH ORP SECTION 5 0 OPERATION WITH REMOTE CONTROLLER 5 2 INFRARED REMOTE CONTROLLER IRC KEY FUNCTIONS The infrared remote controller is used to calibrate and program the transmitter and to read diagnostic messages See Figure 5 3 for a description of the function of the keys RESET Press to end the current oper ation and return to the process display Changes will NOT be saved RESET does not return the transmitter to factory default settings Editing Keys Use the editing keys to change the value of a flashing display The left and r
215. s a fault condition Press ENTER to save lt 13 rWH prompt appears Use the editing keys to change the display to the desired ref 1040 erence electrode high impedance warning value The allowed ranges NEXT ENTER Type of reference electrode Allowed range Low impedance LO in step 11 0 2000 kilohms High impedance HI in step 11 0 2000 megohms Entering 0000 disables the feature When the reference electrode impedance goes above the fault value the transmitter displays the diagnostic message rEFWArn Press ENTER to save 14 The rWL prompt appears Use the editing keys to change the display to the desired ref erence electrode low impedance warning value The allowed ranges are 8000 Type of reference electrode Allowed range Low impedance LO in step 11 not applicable High impedance in step 11 0 900 megohms Entering 0000 disables the feature When the reference electrode impedance goes below the warning value the transmitter displays the diagnostic message rEFWArn Press ENTER to save The prompt appears but is disabled when LO is selected in step 11 PROGRAM 15 The rFL prompt appears Use the editing keys to change the display to the desired ref erence electrode low impedance fault value The allowed ranges are rFL 8000 ENTER Type of reference electrode Allowed range Low impedance LO in step 11 not applicable H
216. s CAL CALIbrAtE will appear Press ENTER CAL bF1 will appear With the sensor in the first buffer be sure the glass bulb and the temperature element are completely submerged i e 3 inches Do not let the weight of the sensor rest on the glass bulb Swirl the sensor to dislodge trapped bubbles Press ENTER bF1 will flash until reading is stable The measured pH value will appear the main display Press until the small number next to bF1 matches the nominal pH buffer value i e 4 01 pH Press ENTER to save the first calibration point CAL bF2 will appear Remove the sensor from the first buffer rinse and place in the second buffer Press ENTER bF2 will flash until the reading is stable The measured pH value will appear in the main display Press or until the small number next to bF2 matches the nominal pH buffer value i e 10 00 pH Press ENTER to save the second calibration point Press RESET to return to the process display The calibration is complete Place the sensor in the process The start up is complete although the following optional procedure may be useful Section 4 Output OPTIONAL A This optional procedure assigns specific pH values to the 4 20 mA output The factory default is set to 0 00 pH at 4 mA and 14 00 pH at 20 mA Press PROG OutPut will appear Press ENTER 4 MA will appear Use the arrow keys to change the displayed number to the desired pH Press ENTER to save 20 MA
217. s PROG the infrared remote controller IRC to enter the Program menu To save new settings press ENTER To leave the Program menu without saving new values press EXIT Pressing EXIT with a prompt showing returns the display to the first prompt in the sub menu Pressing EXIT again returns the transmitter to the process display If program settings are protected with a security code pressing PROG or CAL will cause the Id screen to appear Key in the security code and press ENTER The first sub menu will appear For more information see Section 5 7 Security A transmitter adjacent to the one being programmed may pick up signals from the IRC To avoid accidentally changing settings use a different security code for each nearby transmitter See Section 5 7 Security and Section 8 6 Display Units for details 56 MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS TABLE 8 1 pH Settings List ITEM MNEMONIC DISPLAY LIMITS FACTORY SETTINGS USER SETTINGS PROGRAM LEVEL Sections 8 0 8 9 A Output Range Section 8 3 OutPut 4 mA Output 0 14 pH 0 00 pH 20 mA Output 0 14 pH 14 00 pH Hold HOLd 3 80 to 22 00 mA 21 00mA Dampening dPn 0 to 255 seconds 0 seconds Fault Current Output Setting FAULt 3 80 to 22 00 mA 22 00mA B Diagnostic Section 8 4 dlAgnOStIC 1 Reference Cell Offset Standardize error rOFFSt 0 to 1000 mV 60 mV pH on glass electrode Diagnostics Function dlAg On Off Off Glass Impedance
218. s and the process liquid or piping 2 Strip back the ends of a heavy gauge wire Connect one end of the wire to the process piping or place it in the processliquid Place the other end of the wire in the container of buffer with the sensor The wire makes an electrical connection between the process and sensor 3 If similar symptoms develop after making the connection a ground loop exists no symptoms develop a ground loop may or may not exist B Check the grounding of the process 1 The measurement system needs one path to ground through the process liquid and piping Plastic piping fiber glass tanks and ungrounded or poorly grounded vessels do not provide a path A floating system can pick up stray voltages from other electrical equipment 2 Ground the piping or tank to a local earth ground Metal tees grounding rings or grounding rods may be required 3 If problems persist connect a wire from the the ground connection at the dc power supply to the transmitter case Connect a second wire from the transmitter case to the process These connections force the grounds to the same potential 4 Ifthe problem persists simple grounding is not the problem Noise is probably being carried into the instrument through the sensor wiring Go to step C C Simplify the sensor wiring 1 Disconnect all sensor wires at the transmitter except TB 4 RTD SNS TB 5 RTD IN TB 7 REF IN and TB 10 pH ORP IN If a remote preamplifie
219. se with either external preamplifiers or the transmitters internal pre amplifier a accessible preamplifier is in the sensor or remote junction box use Figure 12 5 b If the preamplifier is in the transmitter or if the sensor has a built in potted preamplifier use Figure 12 6 107 MODEL 3081 pH ORP SECTION 12 0 108 TROUBLESHOOTING Process pH measurement problem Perform buffer calibration outside of the process Refer to Section 7 5 Buffer calibration Likely Process Problem OK or Ground Loop 1 Measure pH of a grab sample in a beaker If pH is correct then the process is OK Resolve the ground loop insu late shield wires from grounded Is transmitter metal See Section 12 5 8 reamplifier switch in Put transmitter preamplifier switch lt Junction box position Ground un grounded processes S 1 into junction box position see Figure 2 2 example all plastic piping Simulate pH through the pream plifier and transmitter Refer to Section 12 8 3 Simulate pH directly into transmitter bypass the pre amplifier See Section 12 8 2 Preamplifier and trans Likely Sensor Problem mitter test OK 1 Verify sensor is compatible with the analyzer Must have PT100 PT1000 or 3K Balco RTD Verify RTD jumpers and temperature YES parameter programming Preamp or Wiring problem Check RTD If bad or wrong use 1 Check wiring manual temperature compensa 2 Replace preamplifier tion
220. should AT POWER SUPPLY be shielded and Mans Sony TERMINAL BLOCK enclosed in an earth OMITTED SENS TO GROUNDING SCREW grounded metal conduit FOR CLARITY AT TRANSMITTER AND Do not run power supply signal wiring the same conduit or cable tray with AC power lines or with relay actuated J signal cables Keep power supply sig N 5 nal wiring at least 6 ft 2 m away from SN O POWER SUPPLY heavy electrical equipment 7 222222 An additional 0 1 mA current loop is available between TB 14 and TB 15 A 1 mA current in this loop signifies a DWG NO sensor fault See Figure 4 3 for wiring 40308122 1 instructions See Section 8 3 or 10 3 POWER SUPPLY and Section 12 0 for more information about sensor faults FIGURE 2 7 Power Supply Current Loop Wiring MODEL 3081 pH ORP SECTION 3 0 WIRING SECTION 3 0 WIRING 3 1 3 2 General Information Wiring Diagrams 3 1 GENERAL INFORMATION pH and ORP sensors manufactured by Rosemount Analytical can be wired to the Model 3081 pH ORP transmitter in three ways 1 directly to the transmitter 2 to a sensor mounted junction box and then to the transmitter 3 to a remote junction box and then from the remote junction box to the transmitter The pH or ORP signal can also be preamplified in one of four places 1 in the sensor 2 in a junction box mounted on
221. sing the problem is not corrected there is a high probability that the system will soon fail A fault alerts the user that a system disabling con dition exists If a fault message is showing all measurements should be regard ed as erroneous When a WARNING condition exists 1 The main display remains stable it does not flash 2 Awarning message appears alternately with the temperature output display See Figure 12 1 See Section 12 4 for an explanation of the different warn ings and suggested ways of correcting the problem When a FAULT exists 1 The main display flashes 2 The words FAULT and HOLD appear in the main display 3 Afault message appears alternately with the temperature output display See Figure 12 2 See Section 12 4 for an explanation of the different fault mes sages and suggested ways of correcting the problem 4 The output current will remain at the present value or go to the programmed fault value See Section 8 3 Output Ranging for pH Measurements or Section 10 3 Output Ranging for ORP Measurements for details on how to program the current generated during a fault condition 5 fthe transmitter is in HOLD when the fault occurs the output remains at the programmed hold value To alert the user that a fault exists the word FAULT appears in the main display and the display flashes A fault or diagnostic message also appears 6 Ifthe transmitter is simulating an output current when the fault occurs the
222. sor may also be in good condition The warning and fail limits are simply set too low 2 Inspect and clean the sensor Refer to Section 11 3 After cleaning the sensor calibrate it following the auto calibration procedure in Section 7 5 Be sure to note the sensor slope If cleaning the sensor reduces the impedance a The sensor is in good condition b Return the calibrated sensor to service If cleaning does not lower the glass impedance and the sensor can be calibrated a The sensor is probably in good condition however it may be nearing the end of its life The electrode slope is a good indicator of remaining life 92 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING SLOPE STATUS OF SENSOR 54 60 mV unit pH Sensor is in Sensor is in good condition condition 48 50 mV unit pH is nearing the end of its life Once the slope drops below 48 mV unit pH the sensor can no longer be calibrated b The Glass Fail High GFH limit is probably set too low for the sensor Set the GFH limit to about 150 megohms greater than the measured glass impedance c Ifthe GLASSWArn message was also flashing raise the GWH limit from its former value by the same amount GFH was raised from its former value If cleaning does not lower the glass impedance and the sensor cannot be calibrated The sensor has failed and should be replaced 12 4 2 GLASSWArn GLASSWArn is an electrode fault message It means the glass impedan
223. t of full scale or milliamps for the output display program a security code 8 6 2 Definitions 1 DISPLAY UNITS Select pH if the transmitter is being used to measure pH Select ORP if the transmitter is being used to measure ORP ORP is oxidation reduction potential ORP has units of millivolts and is usually measured with an inert metal elec trode such as a platinum electrode The units selected are shown in the main display next to the measured value OUTPUT CURRENT DISPLAY The transmitter generates a 4 to 20 mA output signal directly proportional to the pH of the sample The output signal appears on the same line with the temperature The output signal can be displayed as current in mA or as percent of full scale SECURITY CODE The security code unlocks the transmitter and allows complete access to all menus The transmitter is shipped with the security code disabled 8 6 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the dISPLAY sub menu appears Press ENTER The screen displays the tYPE prompt Press or to toggle between pH and Press ENTER to save The screen displays the tEMP prompt Press or to toggle between C F Press ENTER to save The screen displays the OUtPUt prompt Press or v to toggle between and CUR Press ENTER to save The screen displays the COdE prompt Use the editing keys to enter a security code between 001 and 999 Entering 000
224. tance changes about 0 45 per C When dissolved in water bases decrease the hydrogen ion concentration Pure water at 25 C contains 1 x 10 7 moles per liter of hydrogen ions H and an equal concentration of hydroxide ions A base decreases the hydrogen ion con centration below the value found in pure water and increases the hydroxide ion concentration However the product of the hydroxide and hydrogen concentra tions remains constant Alkalai is another word for base A calibration buffer is a solution having accurately known pH Calibration buffers have a nominal pH which is the pH at 25 C Changing the temperature changes the pH value of a buffer Buffers define the pH scale and are used to calibrate the response of pH measurement cells The term buffer generally refers to a solution that resists changes in pH upon dilu tion or the addition of small amount of a strong acid or base Chemical sensors are transducers They produce a signal related to concentra tion or to a physical property Calibration is the process of assigning known con centrations or known physical values to the sensor signal Because the relation ship between sensor output and physical or chemical property is often linear only one or two calibration points are needed MODEL 3081 pH ORP Combination electrode Common Diagnostics Electrode potential Electrochemical cell Electrode Electrolyte Error Error condition Explosion proof
225. teel tag specify marking shipped loose was model option 11 1 16 0 5 kg 9120531 adapter female to two leads 1 16 0 5 kg 9210012 Buffer solution 4 01 pH at 25 C potassium hydrogen phthalate solution NIST 2 Ib 1 0 kg pH scale buffer 16 oz 473 mL 9210013 Buffer solution 6 86 pH at 25 C potassium dihydrogen phosphate and 2 15 1 0 kg sodium hydrogen phosphate solution NIST pH scale buffer 16 oz 473 mL 9210014 Buffer solution 9 18 pH at 25 C sodium tetraborate solution NIST pH scale 2 15 1 0 kg buffer 16 oz 473 mL R508 160Z ORP standard 475 20 mV at 25 iron Il ammonium sulfate and iron III 2 15 1 0 kg ammonium sulfate in 1 M sulfuric acid 16 oz 473 mL 5103081P Instruction manual 1 15 0 5 kg Weights rounded up to nearest pound or nearest 0 5 kg MODEL 3081 pH ORP SECTION 2 0 INSTALLATION SECTION 2 0 INSTALLATION 21 Unpacking and Inspection 2 2 Pre Installation Set Up 2 3 Orienting the Display Board 2 4 Mechanical Installation 2 5 Power Supply Current Loop 2 1 UNPACKING AND INSPECTION Inspect the shipping container If it is damaged contact the shipper immediately for instructions Save the box If there is no apparent damage remove the transmitter Be sure all items shown on the packing list are present If items are miss ing immediately notify Rosemount Analytical Save the shipping container and packaging They can be reuse
226. tem was previously commissioned and operating correctly rEF WArn likely means a real problem exists However if the system is being started up or if the advanced diagnostic feature is being used for the first time rEF WArn could be caused by a miswired sensor or by programmed limits that are not correct for the sensor NOTE rEF WArn is a sensor diagnostic message Sensor diagnostic messages are optional They can be turned off To disable sensor diagnostic mes sages refer to Section 8 4 3 Troubleshooting Flowchart rEF WArn Troubleshooting rEF WArn problems is exactly the same as troubleshooting rEF FAIL problems Refer to Section 12 4 3 12 4 5 CALIbrAtE CALIDrAtE is a diagnostic intended for future use If the CALIbrAtE message is showing go to Section 8 4 and disable CALIbrAte 12 4 6 tEMP HI and tEMP LO tEMP HI and tEMP LO mean the transmitter has detected a problem with the temperature measuring circuit The problem may lie in the sensor the cable or the transmitter The determination of temperature is an integral part of the pH meas urement Therefore failure of the temperature measuring circuit is a system disabling condition However in an emer gency automatic temperature compensation can be disabled and the transmitter placed in manual temperature compensation Refer to Section 8 5 For manual temperature compensation choose a temperature equal to the average temperature of the process The resulting pH reading will be i
227. the board Insert the three bolts through 40008125 A the holes Align the bolts with the stand offs on the analog board and position the FIGURE 2 3 Model 3081 pH ORP Transmitter CPU Board display and CPU boards on the analog board If the boards are properly aligned the bolts will drop in place Press along the bottom of the stack to seat the pin and socket connector Tighten the bolts v 23641 8 Replace the end cap and lock nut 2 3 ORIENTING THE DISPLAY BOARD The display board can be rotated 90 degrees clockwise or counterclockwise from the original position To reposition the display 1 Loosen the cover lock nut until the tab disengages from the circuit end cap Unscrew the cap Remove the three bolts holding the circuit board stack Lift and rotate the display board 90 degrees clockwise or counterclockwise into the desired position Position the display board on the stand offs Replace and tighten the bolts N Replace the circuit end cap 2 4 MECHANICAL INSTALLATION 2 4 1 General information 1 The transmitter tolerates harsh environments For best results install the transmitter in an area where temperature extremes vibrations and electromagnetic and radio frequency interference are minimized or absent 2 To prevent unintentional exposure of the transmitter circuitry to the plant environment keep the security lock in place over the circuit end cap To remove the c
228. the problem must lie with the sensor or the interconnecting wiring Verify the interconnecting wiring point to point Fix or replace bad cable If cable is good replace the pH sensor If the transmitter does not respond to simulated inputs replace the board stack PN 23574 02 12 5 7 Buffer Calibration Is Acceptable Process pH is Slightly Different from Expected Value Differences between pH readings made with an on line instrument and a laboratory or portable instrument are normal The on line instrument is subject to process variables for example grounding potentials stray voltages and orientation effects that do not affect the laboratory or portable instrument To make the Model 3081 pH ORP transmitter match the reading from a second pH meter refer to Section 7 7 104 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 5 8 Buffer Calibration Is Acceptable Process pH is Grossly Different from Expected Value The symptoms suggest a ground loop measurement system connected to earth ground at more than one point a float ing system no earth ground or noise being induced into the transmitter by sensor cabling The problem arises from the process or installation It is not a fault of the transmitter The problem should disappear once the sensor is taken out of the system A To confirm a ground loop 1 Verify that the system works properly in buffers Be sure there is no direct electrical connection between the buffer container
229. the product Install your equipment as specified in the Installation Instructions of the appropriate Instruction Manual and per applicable local and national codes Connect all products to the proper electrical and pressure sources To ensure proper performance use qualified personnel to install operate update program and maintain the product When replacement parts are required ensure that qualified people use replacement parts specified by Rosemount Unauthorized parts and procedures can affect the product s performance and place the safe operation of your process at risk Look alike substitutions may result in fire electrical hazards or improper operation Ensure that all equipment doors are closed and protective covers are in place except when maintenance is being performed by qualified persons to prevent electrical shock and personal injury CAUTION If a Model 275 Universal Hart If a software modification is required Communicator is used with these please contact your local Emerson Process transmitters the software within the Management Service Group or National Model 275 may require modification Response Center at 1 800 654 7768 Emerson Process Management Rosemount Analytical Inc 2400 Barranca Parkway Irvine CA 92606 USA Tel 949 757 8500 949 474 7250 nasa I Rosemount Analytical Inc 2004 Process Management 4 4 WHAT YOU NEED TO KNOW BEFORE INS
230. tion 2 2 Also program the transmitter to recognize the 3K RTD see Section 8 5 for pH or 10 5 for ORP 16 MODEL 3081 pH ORP SECTION 3 0 WIRING Table 3 7 Wiring Diagrams for Model 385 Sensors Sensor Junction Box Preamplifier RTD Wire Functions Wiring Diagram 385 02 in sensor mounted junction box Pt 100 Figure 3 15 Figure 3 16 385 04 remote in remote junction box Pt 100 Figure 3 10 Figure 3 12 Table 3 8 Wiring Diagrams for Model 381 Sensors Table 3 9 Wiring Diagrams for Model 381pHE and 381pH Sensors Sensor Junction Box Preampliier RTO Wire Functions Wiring Diagram 381 pHE 31 42 52 remote in remote junction box Pt 100 Figure 3 3 Figure 3 5 Table 3 10 Wiring Diagrams for Model 328A Sensor Sensor Junction Box Preamplifier RTD Wiring Diagram 328A 17 Figure 318 Table 3 11 Wiring Diagrams for Model 320HP Sensor Sensor Junction Box Preamplifier RTD Wiring Diagram 1 320HP 10 55 on mounting plate Pt 100 Figure 3 19 320HP 10 58 on mounting plate in junction box attached to mounting plate Pt 100 Figure 3 20 Sensors have a BNC connector that the Model 3081 pH ORP transmitter does not accept Cut off the BNC and terminate the coaxi al cable as shown in Figure 3 23 Alternatively use a BNC adapter PN 9120531 Set the RTD jumper to the 3K position see Section 2 2 Also program the transmitter to recognize the 3K RTD see Section 8 5 for pH or 10 5 for OR
231. transmitter continues to generate the simulated current To alert the user that a fault exists the word FAULT appears in the display and the display flash es BLASSUIAr n FIGURE 12 1 Warning Annunciation When a non disabling problem occurs warning message appears alternately with the temperature out put display F A L T H o 1 D SLASSFA L FIGURE 12 2 Fault Annunciation When a disabling condition a fault occurs the display appears as pic tured above To further alert the user that measurements are in error the display flashes Diagnostic mes sages appear in the ature output area on the screen 89 MODEL 3081 pH ORP SECTION 12 0 TROUBLESHOOTING 12 2 CALIBRATION ERRORS If an error occurs during calibration an error message appears in the main display and the transmitter does not update the calibration The calibration errors are Std Err SLOPE Err LO and SLOPE Err See Section 12 4 for an explana tion of the error messages and suggested ways of correcting the problem 12 3 TROUBLESHOOTING GENERAL Troubleshooting is easy as 1 2 3 Step 1 Look for a diagnostic message on the display to help identify the problem Refer to Section 12 4 for an explana tion of the message and a list of the possible problems that triggered it Step 2 Refer to Section 12 5 for common measurement problems and the recommended actions to resolve them Step 3 Follow the step by step trou
232. ts are pH 0 00 to pH 14 00 The default is pH 7 00 Press ENTER to save NOTE Do NOT change the isopotential pH of the transmitter unless you are thor oughly familiar with the role of sensor and transmitter isopotential points in pH measurement OR unless the sensor operating instructions specif ically state that the isopotential pH is a value other than pH 7 Press EXIT to return to the process display MODEL 3081 pH ORP PROGRAM SIM OUTPUT EXIT NEXT ENTER PROGRAM tESt EXIT ENTER SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 9 GENERATING A TEST CURRENT 8 9 1 Purpose This section describes how to generate output currents for testing recorders and data han dling systems 8 9 2 What happens while the transmitter is generating a test current 1 The output current goes to the programmed test value and remains there until the TEST function is disabled The main display continues to show the pH of the process stream The word HOLD appears in the display The test current value supersedes both the HOLD value and the FAULT value If a fault occurs while the transmitter is generating the test current the word fault appears in the display and the display flashes 8 9 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the SIM OUtPUt sub menu appears Press ENTER The tESt prompt appears Use the editing keys to change the number to the desired value The al
233. ts or fouls the sensor frequent cleaning may be necessary If the process does not contain a high level of suspended solids the need for regular cleaning will be less 11 4 2 Cleaning Procedures The platinum electrode is easily cleaned by using a tissue to rub the metal surface with a paste of baking soda sodium bicarbonate A clean platinum electrode is bright and shiny 11 4 3 Checking the Reference Electrode ORP electrodes manufactured by Rosemount Analytical have a silver silver chloride reference Section 11 3 3 describes how to check the performance of the reference electrode 11 5 CALIBRATION 11 5 1 General Many users regard calibration as a routine part of sensor transmitter maintenance Procedures for calibrating pH sensors ORP sensors and general information regarding the use of pH calibration buffers and ORP standards are given in Sections 7 0 Calibration of pH Measurements 9 0 Calibration of ORP Measurements 13 0 pH Measurements and 14 0 ORP Measurements 11 5 2 Calibration Frequency The frequency at which sensors should be calibrated can be determined only by experience Many factors influence cali bration frequency Sensors installed in dirty or corrosive process streams usually require more frequent calibration than sensors used in clean water Sensors measuring extreme pH values particularly high pH also require more frequent cali bration than sensors measuring mid range pH The width of the pH or ORP control rang
234. tter and sensor isopotential pH the smaller the error when the calibration and measurement temperatures are different The default isopotential value for the transmitter is pH 7 Most sensors have an isopotential point fairly close to pH 7 so the default value rarely needs changing For more information consult Section 13 8 Isopotential pH Some sensors have an isopotential pH distinctly different from pH 7 For these sensors the transmitter isopotential pH must be changed to match the sensor NOTE Do NOT change the isopotential pH of the transmitter unless you are thoroughly familiar with the role of sensor and transmitter isopotential points in pH measure ment OR unless the sensor operating instructions specifically state that the isopotential pH is a value other than pH 7 OPERATING ISOPOTENTIAL pH The operating isopotential pH is a mathematical combina tion of the solution temperature coefficient and the meter isopotential pH Changing the solu tion temperature coefficient ALWAYS changes the operating isopotential pH When program ming the transmitter to perform a solution temperature compensation it is ALWAYS better to enter the solution temperature coefficient and allow the transmitter to calculate the operating isopotential pH 69 MODEL 3081 pH ORP PROGRAM IGOPOtatRL 1 EXIT NEXT ENTER 2 3 PROGRAM 1COEFF 000 EXIT NEXT ENTER PROGRAM 150 1100 NEXT ENTER
235. ult value is 60 mV 2 GLASS IMPEDANCE TEMPERATURE COMPENSATION In certain applications the use of a glass i e pH electrode as a refer ence electrode may be required The impedance of a glass electrode changes with temperature For changes in glass impedance to be a useful indicator of electrode condition the impedance measurement must be corrected to a reference temperature 3 REFERENCE IMPEDANCE The majority of reference electrodes used in industry are low impedance silver silver chloride elec trodes However there are applications that call for either a high impedance sodium or pH glass reference electrode Both high impedance and low impedance reference electrodes can be used with the Model 3081 pH ORP transmitter 4 WARNING AND FAILURE LIMITS FOR THE REFERENCE ELECTRODE Warning tells the user that the reference electrode impedance is approaching the failure limit Low and high warning and failure limits are programmable For conventional silver sil ver chloride reference electrodes only the high limits are useful For high impedance reference electrodes both low and high lim its are used Figure 10 1 shows suggested limits for low impedance reference electrodes Figure 10 2 shows suggested limits for high impedance glass reference electrodes a o lt High impedance fault 140 kilohms gt High impedance fault 1500 megohms High impedance warning 1000 megohms Reference Impedance kilohms a e o lt
236. ween 0 and 900 megohms Entering 0000 disables the feature When the glass electrode impedance drops below the fault value the transmitter displays the diagnostic message GLASS FAIL and sets a fault condition Press ENTER to save The CAL prompt appears This diagnostic is intended for factory use The default value 000 should appear If 000 is not showing use the editing keys to change the display to 000 Press ENTER to save The rEF prompt appears Press or until the desired setting appears LO identifies a low impedance reference electrode and HI identifies a high impedance reference electrode Press ENTER to save Selecting LO disables the low impedance warning and failure limits for the reference electrode NOTE Be sure the jumpers on the analog board are set to match the reference electrode impedance See Section 2 2 Pre Installation Set Up MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS PROGRAM 12 The rFH prompt appears Use the editing keys to change the display to the desired ref erence electrode high impedance fault value The allowed ranges are ioo EXIT NEXT ENTER Type of reference electrode Allowed range Low impedance LO in step 11 0 2000 kilohms High impedance in step 11 0 2000 megohms Entering 0000 disables the feature When the reference electrode impedance goes above the fault value the transmitter displays the diagnostic message rEFFAIL and set
237. well as common commercial buffers Commercial buffers which are sometimes called technical buffers are traceable to standard buffers but the accuracy of commer cial buffers is generally less than standard buffers Tables 8 2 and 8 3 list the buffers the Model 3081 pH ORP trans mitter recognizes and the temperature range over which the buffer pH is defined TABLE 8 2 pH values of standard buffer solutions and the temperature range over which pH values are defined ST pH pH f eH 5 95 168 5 95 168 0 95 168 29 __ ToO T 38 ee eee eee eee 6 86 0 05 686 0 95 6 86 see note NOTE pH 7 buffer is not a standard buffer Because it is a popular commercial buffer in the United States it is included with the standard buffers The pH of the buffer is defined between 0 and 95 67 MODEL 3081 pH ORP SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS TABLE 8 3 pH values of commercial technical buffers and the temperature range over which pH values are defined 3 STABILITY CRITERIA For the Model 3081 pH ORP transmitter to accept calibration data the pH must remain within a specified range for a specified period of time The default values are 0 02 pH units and 10 seconds In other words at the default setting calibration data will be accepted as soon as the pH reading is constant to within 0 02 units for 10 seconds The minimum range is 0 01 and the maximum time
238. ws suggested limits for will also be high if the sensor is out of the process liquid high impedance glass reference elec trodes High impedance fault 1500 megohms 1000 High impedance warning 1000 megohms E Low impedance warning 20 megohms 10 lt Low impedance fault 10 megohms Glass reference electrode impedance megohms FIGURE 8 3 Suggested Warning and Failure Limits for High Impedance Glass Reference Electrodes The limits for a high impedance glass reference electrode are the same as the limits for a high impedance glass measuring electrode MODEL 3081 pH ORP PROGRAM 05 0 ENTER PROGRAM INP C EXIT NEXT ENTER PROGRAM GFH 500 EXIT ENTER 62 SECTION 8 0 PROGRAMMING FOR pH MEASUREMENTS 8 4 3 Procedure Press PROG on the infrared remote controller IRC Press NEXT until the diAGnOStIC sub menu appear Press ENTER The screen displays the rOFFSt prompt Use the editing keys to change the flashing display to the desired standardization reference offset in millivolts The range is 0 to 1000 mV Press ENTER to save The prompt appears Use or to enable or disable OFF the sensor diagnostics Press ENTER to save The prompt appears Use or to enable On or disable OFF glass imped ance temperature compensation Because glass impedance is a strong function of tem perature correcting glass impedan

Emerson Process Management - Emerson Electric Co. Microphone 3081 pH/ORP User's Manual

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