GDS GDS-78XP User Manual
Contents
1. Sample Flow Meter Regulator 1200 0043 Filter Drain Filter Bypass Pressure Gauge 1200 0044 Filter Combination Run Cal Valve Flow Meter 1200 0167 1200 0037 1200 0451 Filter Element Kit 1200 0169 Figure 12 6 Sample Conditioning Option 3 with Flow Switch amp GDS IR Spare parts Page 45 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Sensor Head Assembly 10 0247 lt Sensor Head Base Sensor 10 98XX RYYYY Ss Sensor Head Cover Figure 12 7 GDS 78XP Sensor Head Exploded View Page 46 GDS 78XP Operation amp Maintenance Manual Revision 2 0 17 Flex Tubing ii 2 1 Run Cal Valve Sample Outlet Sample Flow Meter Cal Gas Inlet Filter Drain Figure 13 1 GDS 78XP Dimensions Plate Page 47 GDS 78XP Operation amp Maintenance Manual Revision 2 0 8 4 216 25 6 Figure 13 2 GDS 78XP Dimensions NEMA 4X Stainless Enclosure Page 482. __ Gas and Flame Detection Operation and Maintenance Manual GDS 78XP Process Monitor for Hazardous Area Applications AUTHORIZED DISTRIBUTOR GasDetectorsUSA com Houston Texas USA GasDetectorsUSA com 832 615 3588 GDS 78XP Operation amp Maintenance Manual Revision 2 0 CAUTION FOR SAFETY REASONS THIS EQUIPMENT MUST BE OPERATED AND SERVICED BY QUALIFIED PERSONNEL ONLY READ AND UNDERSTAND INSTRUCTION MANUAL COMPLETELY BEFORE OPERATING OR SERVICING ATTENTION POUR DES RAISONS DE S CURIT CET QUIPEMENT DOIT TRE UTILIS ENTRETENU ET R PAR UNIQUEMENT PAR UN PERSONNEL QUALIFI TUDIER LE MANUE D INSTRUCTIONS EN ENTIER AVANT D UTILISER D ENTRETENIR OU DE R PARER L QUIPEMENT REVISION HISTORY Revision 2 0 5 20 14 Revised and Updated for GASMAX CX Copyright 2014 GDS Corp All Rights Reserved P N 1200 0712 02 Page 2 GDS 78XP Operation amp Maintenance Manual Revision 2 0 1 SAFETY INFORMATION 6 2 OVERVIEW 7 Introduction 7 Explosion Proof Installation 7 Intrinsically Safe Installation 7 3 HARDWARE 8 Overview 8 Sensor Considerations 8 4 INSTALLATION 10 Selecting a Location 10 Ethernet Connection 10 USER Power amp Signal Connections 11 Relay Connections Optional 11 MODBUS Connections Optional 12 AC Heater Optional 13 Sample Inlet 13 Filter Drain amp Filter Bypass 14 Sample Exhaust 15 Installation Summary Do s and Don
3. GDS 78XP Operation amp Maintenance Manual Revision 2 0 3 The screen will display APPLY ZERO Allow a few seconds for the reading to stabilize and press the EDIT key to complete the ZERO calibration A ZERO CAL SUCCESSFUL message should appear 4 Ifnotalready done set the Run Cal value to the CAL position and connect the cylinder of span gas 5 When the APPLY SPAN message appears turn on the regulator and verify flow on the flow meter After the reading is stable approximately 1 2 minutes press the EDIT key to complete the SPAN GAS calibration If the SPAN calibration is successful the display flashes REMOVE CAL GAS and starts the CAL PURGE delay 6 Immediately shut off the regulator and set the Run Cal valve to RUN At the end of the CAL PURGE delay the GDS 78XP output is re enabled and the unit is fully operational Fixed Flow Regulator Cylinder of Span Gas or Zero Air Figure 6 1 GDS 78XP Calibration Setup Page 19 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Once setup is complete user intervention is not required and the GDS 78XP automatically measures and outputs the gas concentration on a continuous basis NORMAL MAINTENANCE Standard maintenance for the GDS 78XP consists of periodic checks on flow settings and sensor calibration Each time a toxic sensor is calibrated a Sensor Life reading will appear that gives an approximate indication of t
4. 03 33 2 Fault Out 03 32 2 Fault In that occur Events include cold boot system boot alarm reset remote alarm reset log cleared config edit A1 A2 and A3 in and out fault in and out calibration in and out calibration fail communications error config error and marker event Ch 1 Sensr Found Clear Event Log Clears all entries in the event log Life 100 Ch 2 No Sensor View Sensor Life Menu Life Computed value based on initial stored gain value when sensor was first calibrated If new gain equals original gain sensor life 100 If new ain equals twice original gain sensor life gt 096 8 q ginal gain Figure 10 6 System Settings Menu Tree Page 30 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Diagnostics Menu The Diagnostics page provides tools for use during setup or testing Tests for optional features are not available if the feature is not installed Diagnostics Relays Analog Inputs Analog Outputs TESE Serial Ports ADC Readings warning Diagnostic mode Alarms will not Be processed FUNCTION AND REQUIRES A DEVICE REBOOT ON EXIT WARNING ENTERING DIAGNOSTICS MODE DISABLED ALARM Edit OK Next Cancel Relays Relays Menu Relay 1 off Relay 2 off Allows individual relays to be turned on or off under user control Only Relay 3 off Fault Relay on available if optional Relay Modbus board is installed Ch 1 EC Loc Counts 856 Tem
5. amp Maintenance Manual Revision 2 0 Display 10 0387 1 O Board 10 0390 Optional Relays amp MB 10 0388 Sensor Head 10 0247 Sensor 10 98xx Smart Sensor Flow Cell 10 0205 Filter Pyrex Run Cal Valve Flow Meter 2000 0139 1200 0037 1200 0451 Flow Switch Filter Element 1200 0224 2000 0140 Figure 12 1 Sample Conditioning Option 1 with Flow Switch Spare parts Page 40 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Display 10 0387 UO Board 10 0390 Optional Relays amp MB Sample Flow Meter 10 0388 N A Sensor GDS IR Tn O specify gas Sensor Flow Cell 10 0271 o Sample Outlet Cal Gas Inlet Filter Drain Filter Pyrex Run Cal Valve Flow Meter 2000 0139 1200 0037 1200 0451 Flow Switch Filter Element 1200 0224 2000 0140 Figure 12 2 Sample Conditioning Option 1 with Flow Switch amp GDS IR Spare parts Page 41 Inlet Filter Drain Filter Stainl
6. extraction The GDS 78XP back plate is an industry standard size and features mounting holes that can be used to securely attach the monitor to a bulkhead or wall Make sure there is sufficient clearance to install the sample inlet tubing and sample outlet tubing Also make sure that the Run Cal valve can operate freely and that access to the Cal Port is not blocked for any reason Power Input Signal Output de Sample Sample Inlet Sample Outlet d Cal Gas Inlet Sample Outlet Sample Inlet Filter Drain Figure 4 1 GDS 78XP Process Monitor with XP Flow Switch and GDS IR Sensor ETHERNET CONNECTION The GASMAX CX gas monitor includes a standard RJ 45 Ethernet connection on the main I O board Both fixed IP and DHCP based dynamic IP addressing is supported The GASMAX CX supports a full range of MODBUS TCP accessible register see Chapter 10 as well as a built in web server with data display and gas detector configuration page See Figure 5 2 Page 10 GDS 78XP Operation amp Maintenance Manual Revision 2 0 USER POWER amp SIGNAL CONNECTIONS To access the power and signal wiring remove the cover from the explosion proof enclosure Connect a source of 24VDC to 18
7. ts 15 5 SETUP amp OPERATION 16 Flow Setup 16 GASMAX CX Display 16 Alarm Setup 17 Page 3 GDS 78XP Operation amp Maintenance Manual Revision 2 0 6 CALIBRATION 7 MAINTENANCE Normal Maintenance Fault and Overrange Conditions Sensor Replacement 8 TROUBLESHOOTING GUIDELINES 9 SPECIFICATIONS 10 11 12 13 USER MENUS MODBUS REGISTERS SPARE PARTS DRAWINGS AND DIMENSIONS Page 4 18 20 20 20 21 22 24 25 32 40 47 GDS 78XP Operation amp Maintenance Manual Revision 2 0 TABLE OF FIGURES FIGURE 3 1 GDS 78XP PROCESS MONITOR WITH XP FLOW FIGURE 4 1 GDS 78XP PROCESS MONITOR WITH XP FLOW SWITCH AND GDS IR SENSOR FIGURE 4 2 GDS 78XP POWER SIGNAL amp ETHERNET WIRING eee FIGURE 4 3 RELAY MODBUS GONNEZTTONS rru FIGURE 4 4 MODBUS WIRING JUNCTION BOX rss FIGURE 4 5 200W AC HEATER MARINO rrura FIGURE 4 6 FILTER DRAIN amp EXHAUST TUBING 5 FIGURE 5 1 GDS 78XP GASMAX DISPLAY SEQUENCE DISPLAY SCREEN amp TREND SCREEN FIGURE 6 1 GDS 78XP CALIBRATION SETUP eene nennen nennen nennen FIGURE 10 1 MAIN MENU TREE dee rper eror e Eate FIGURE 10 2 ALARM OUTPUTS MENU TREE FIGURE 10 3 CHANNEL SETTINGS MENU TREE 1 rrura FIGURE 10 4 CHANNEL SETTINGS MENU TREE
8. Time Sets the system date and time Used for display and event Digital Input View Event Log Clear Event Log Warm Up Delay Sets length of time in minutes from power on to output View Sensor Life log entries signals active During Warmup Delay the 4 20mA outputs are set to 4mA Cal Purge Delay Sets length of time in minutes that outputs are disabled following a zero or span calibration Configure Block Negative If YES blocks screen from showing negative values Unit 44 1000 ZE P Date 01 25 2013 Send Sensor Life If YES enables transmission of sensor life data across 4 Time 04 33 05 20mA output see GASMAX CX manual for more details Warmup al Cal Purge m 1 InCal mA Sets the 4 20mA output value to be transmitted during a Block Neg NO Send SensrLife No InCal mA 0 00 Alarm Refresh See GASMAX CX manual Alm Refresh m 0 calibration sequencer Enables remote devices to track In Cal status Digital Input Menu Digital Input Mode Determines action if digital input fault ack input is activated Mode Flt Override Normally If Normally OPEN the action will occur if the contacts close if Normally Open Channel Ch 1 amp 2 normally CLOSED the event will occur if the contacts open Channel Determines which channel output is affected Hh mm Ch Event 01 25 2013 03 35 2 Fault Out Event Log 03 34 2 Fault In Event Log Format The event log includes the date time and list of events
9. output from all electrochemical sensors and allowing the sample to exhaust directly to atmosphere will minimize these affects Long runs of tubing connected to the sample outlet may increase the backpressure inside the sensor flow cell and cause higher than normal readings Hydrogen sulfide for example is a heavy gas and will tend to back up inside sample exhaust lines that extend vertically for too great a distance IMPORTANT DO NOT RESTRICT SAMPLE EXHAUST OUTLET PRESSURE IN THE SAMPLE FLOW CELL MAY DAMAGE THE SENSOR AND WILL RESULT IN INCORRECT READINGS IMPORTANT WHEN INSTALLING THE GDS 78XP OUTDOORS MAKE SURE SAMPLE EXHAUST IS PROTECTED BY A SCREEN OR FILTER TO KEEP INSECTS FROM ENTERING THE EXHAUST PORT AND NESTING IN THE SENSOR FLOW CELL DANGER MAKE SURE EXHAUST GAS IS DIRECTED AWAY FROM PERSONNEL AND EQUIPMENT ESPECIALLY SUMPS OR LOW LYING AREAS WHERE HEAVY GASES SUCH AS HYDROGEN SULFIDE CAN BUILD UP OVER TIME HYDROGEN SULFIDE OR OTHER TOXIC GASES ARE DEADLY AND EXPOSURE CAN RESULT IN INJURY OR DEATH INSTALLATION SUMMARY DO S AND DON TS Select an installation location that protects the unit from shock vibration and damage e Always mount the GDS 78XP vertically to ensure proper operation of the low flow switch e sure the power wiring is appropriate for the DC load and distance e Keep DC signal wiring and AC heater wiring separate e Make sure sample conditioning is appropriate to the quality of the sample Obse
10. the GDS 78XP has a menu driven user interface that allows the operator to review and adjust a wide range of settings In the GDS 78XP channel 1 of the GASMAX CX measures the raw sensor gas level and channel 2 provides continuous display output and alarming on the stored value retained in the sequencer memory To access the Main Menu activate the EDIT key with a magnetic wand Main Menu Alarm Outputs Channel settings Comm Settings Security System Diagnostics Alarm Outputs Alarm Output Menu contains settings that control the four optional elay gt 1 2 gt sp i r b beg 3 gt alarm relays if installed These setting include relay programming on and off delay failsafe mode and specific input override Channel settings Channel 1 Channel Settings Menu contains settings specific to each channel Channel 2 gt These include tag names range calibration settings and alarm levels Comm Settings COMM 1 Settings Comm Settings Menu contains settings specific to the Ethernet COMM 2 Settings Nee M ieee network interface MODBUS TCP interface and optional RS 485 serial Troubleshooting ports if installed Security Code to Lock Modbus Web Code 1234 aan or all of the features as well as provide a programmed contact name Security Settings Menu allows the user to restrict operation for some System Settings Menu contains settings that are unit specific These Configure Digital In
11. 1 pins 1 and 4 as shown below Analog 4 20mA signal output is connected to TB1 pin 2 Channel 2 output on pin 3 is not used in this application Terminal Block TB1 1 Power Input 18 30V 2 Channel 1 Output 3 Channel 2 Output Not used 4 Power Ground Ethernet Connection Figure 4 2 GDS 78XP Power Signal amp Ethernet Wiring RELAY CONNECTIONS OPTIONAL The optional GASMAX CX Relay dual MODBUS RTU slave interface is connected piggyback to the back of the GASMAX CX Display Assembly and supplies three level alarm relays a FAULT relay and dual RS 485 Modbus RTU serial ports Remote Alarm Acknowledge 7 Modbus Wiring Modbus A Modbus B Shield Tie Point Modbus A Modbus B Relay Wiring Fault 1 NC Fault 1 Common Fault 1 NO Relay 3 NC Relay 3 Common Relay 3 NO Relay 2 NC Relay 2 Common Relay 2 NO 10 Relay 1NC 11 Relay 1 Common 12 Relay 1 NO b 0000900000090 Figure 4 3 RELAY MODBUS Connections Relays K1 2 and provide a contact closure if the Alarm 1 K1 or Alarm 2 K2 or Alarm 3 limits are exceeded Alarms can be programmed to trigger above or below a certain value work as normal or failsafe and can be made to latch if desired Relay K3 indicates a FAULT condition in the sensor microprocessor or flow system Page 11 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Remote Alarm Reset ca
12. 2 rrura FIGURE 10 5 COMM SETTINGS MENU sss sees eee enen FIGURE 10 6 SYSTEM SETTINGS MENU TREE sss sees eee eee FIGURE 10 7 DIAGNOSTICS MENU TREE rra FIGURE 12 1 SAMPLE CONDITIONING OPTION 1 WITH FLOW SWITCH SPARE PARTS FIGURE 12 2 SAMPLE CONDITIONING OPTION 1 WITH FLOW SWITCH amp GDS IR SPARE PARTS FIGURE 12 3 SAMPLE CONDITIONING OPTION 2 WITH FLOW SWITCH SPARE PARTS FIGURE 12 4 SAMPLE CONDITIONING OPTION 2 WITH FLOW SWITCH amp GDS IR SPARE PARTS FIGURE 12 5 SAMPLE CONDITIONING OPTION 3 WITH FLOW SWITCH SPARE PARTS FIGURE 12 6 SAMPLE CONDITIONING OPTION 3 WITH FLOW SWITCH amp GDS IR SPARE PARTS FIGURE 12 7 GDS 78XP SENSOR HEAD EXPLODED VIEW rrura FIGURE 13 1 GDS 78XP DIMENSIONS nennen FIGURE 13 2 GDS 78XP DIMENSIONS NEMA 4X STAINLESS ENCLOSURE Page 5 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Important Read Before Installation Users should have a detailed understanding of GDS 78XP operating and maintenance instructions Use the GDS 78XP only as specified in this manual or detection of gases and the resulting protection provided may be impaired Read the following WARNINGS prior to use WARNINGS e GDS 78XP process monitor described in this manual must be installed operated and maintained in accordance with information contained herein Installation in any
13. 2021 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Cal Span Value 42023 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Zero Value 42025 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Span Value 42027 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Fault Value 42029 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Alarm 1 Setpoint 42031 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Alarm 2 Setpoint 42033 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Alarm 3 Setpoint 42035 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Manual Gain 42037 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Manual Offset 42039 3 N A Modbus 32 bit IEEE 754 Floating Pt Page 36 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Ch 1 Max Raw 43033 3 N A Binary 4000 Ch 1 Remote ID 43034 3 N A Binary Ch 1 Interface 43035 3 N A Binary Ch 1 Byte Order 43036 3 N A Byte order Ch 1 Alias 43037 3 N A Binary 32 bit 2x Ch 1 IP Address 43039 3 N A Binary 4x unsigned bytes Ch 1 Port 43041 3 N A Binary 32 bit 2x Ch 1 Remote Sensor 43043 3 N A Binary Page 37 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Ch 2 Alarm 1 On Delay 43203 3 N A Activation delay in seconds Ch 2 Alarm 1 Off Delay 43204 3 N A Deactivation delay in minutes Ch 2 Alarm 1 Hysteresis 43205 3 N A Percent of scale Page 38 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Page 39 GDS 78XP Operation
14. N The GDS 78XP is designed for use in Class 1 Division 1 hazardous areas Installation in these areas should follow best industry standard practices and all appropriate electrical codes Generally these codes require rigid metal conduit poured seals and other installation elements necessary to ensure safety For maximum protection against RF interference or electrical surge the GDS 78XP enclosure and interconnecting conduit must be properly grounded INTRINSICALLY SAFE INSTALLATION The GDS 78XP is not designed or certified for use as an Intrinsically Safe device Page 7 GDS 78XP Operation amp Maintenance Manual Revision 2 0 OVERVIEW The GDS 78XP uses low cost reliable electrochemical sensors to detect hydrogen sulfide mercaptan THT and other trace gases in process streams that contain little or no oxygen As electrochemical sensors require oxygen to operate the GDS 78XP alternatively exposes the sensor to the process flow and then purges the sensor with ambient air to maintain the sensor in a sensitive oxygenated state Power Input Signal Output Flow Switch Flow Meter GASMAX CX Gas Monitor Sensor amp Flow Cell b Sample T Outlet n Sample H Inlet iil Run C
15. Open connection will open automatically if the alarm activates or if power is lost Override Allows the relay to be dedicated to a specific channel alarm level or function such as calibration Settings that involve calibration allow the relay to be connected to a cylinder of calibration gas via a solenoid valve to enable automatic application of calibration gas if the unit is placed in Cal Mode Ch1 2 Cal Zero 1 Cal Span Ch2 Cal Span 1 2 Cal Zero Span Figure 10 2 Alarm Outputs Menu Tree Page 26 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Channel Settings Menu The Channel Settings Menu allows the user to adjust individual channel or sensor specific features Data in the Channel Settings Menu is uploaded from Smart Sensors and written back to any local Smart Sensor if changed in the menu Channel Settings Channel 1 gt 1 2 gt 2 events The fault relay is always dedicated to fault events Both channel setup menus are identical so only one is shown Channel x Alarm 1 Alarm 2 Alarm 3 Fault Alarm Data From Temp Comp Configure calibrate All three relay outputs are identical and can be set to respond to channel 1 or channel Alarm X menu all three alarm setting menus are identical Set Point is the engineering unit value where the alarm trips It may be negative or positive 1 bu Latching YES causes the alarm to remain active even after the e
16. al Valve Figure 3 1 GDS 78XP Process Monitor with XP Flow Switch At the beginning of each sequence the GDS 78XP performs Conditions the Sensor by allowing a small sample of gas to enter the SENSOR CONSIDERATIONS For toxic gases the GDS 78XP supports wide range of electrochemical echem sensors These sensors use chemical reactions to sense the presence of gases such as hydrogen sulfide sulfur dioxide and many others Each sensor contains an amount of chemical electrolyte that reacts with the target gas to create free electrons that are amplified and measured Once the electrolyte is depleted sensor output will diminish and the sensor must be replaced Page 8 GDS 78XP Operation amp Maintenance Manual Revision 2 0 IMPORTANT TOXIC SENSORS ARE SUBJECT TO ACCELERATED DETERIORATION IF POWER IS NOT APPLIED WITHIN 3 MONTHS OF SHIPMENT FROM GDS CORP For combustible gases the GDS 78XP supports both a traditional catalytic bead cat bead sensor and the GDS IR infrared sensor Catalytic bead sensors burn combustible gas using a catalyst that operates at high temperature An increase in temperature indicates the presence of gas Catalytic bead sensors can detect any combustible gas but the fact that the active bead is in direct contact with the gas can result in damage or reduced sensitivity if the gas contains chemicals that deactivate or temporarily inhibit the operation of the catalyst Cat
17. ally to release any built up liquid that may have been trapped inside the filter Conversely the filter drain valve may be left cracked open to allow moisture and sample gas to escape on a continuous basis Models with the combination coalescing and membrane filter include a bypass valve that should be opened slightly to maintain a constant flow of sample across the membrane element to carry away moisture and particulates captured by the filter Filter Drain Recommendations 1 Including a length of clear tubing in the filter drain line makes it easy to monitor the drain for the presence of moisture 2 Filter drain and filter bypass drain can be combined in the same manifold Filters in sample draw units should only be drained during sample purge or purge hold times to keep ambient air from being drawn into the GDS 78XP by the sample pump IMPORTANT DO NOT TIE SAMPLE EXHAUST TO A COMMON EXHAUST MANIFOLD MAINTAIN A SEPARATE SAMPLE EXHAUST LINE TO AMBIENT AIR Figure 4 6 Filter Drain amp Exhaust Tubing Recommendations NOTE IF SUFFICIENT PRESSURE EXISTS IN THE INPUT LINE LEAVING THE FILTER DRAIN VALVE CRACKED OPEN WILL ALLOW SAMPLE GAS TO FLOW FROM THE PICKUP POINT TO THE GDS 78XP ON A CONTINUOUS BASIS ENSURING THAT FRESH SAMPLE IS ALWAYS AVAILABLE AT THE SENSOR Page 14 GDS 78XP Operation amp Maintenance Manual Revision 2 0 SAMPLE EXHAUST Changes in ambient pressure will affect the
18. alytic material is used each time the sensor is exposed to combustible gas and as a result the sensor will lose sensitivity over time Infrared sensors use the fact that hydrogen carbon bonds found in all hydrocarbon gases absorb infrared light at certain frequencies The sensor is designed such that the target passes between the source and detector and a reduction in detector output indicates the presence of gas Infrared sensors cannot be poisoned or damaged by chemicals in the target gas and typically have a long life GDS IR sensors carry a 5 year warranty on the electronics and a 12 year warranty on the IR source IMPORTANT INFRARED SENSORS CANNOT DETECT COMBUSTIBLE LEVELS OF HYDROGEN GAS Photoionization detectors PID sensors are used to detect volatile organic compounds such as benzene or toluene PID sensors use high energy ultraviolet light to partially ionize complex molecules and measure the resulting free electrons Each VOC has a different ionization potential IP energy level that is measured in electron volts or eV and a given PID sensor will detect all compounds present with IP values that are equal to or lower than the rated eV of the PID sensor lamp PID sensor lamps eventually wear out and can be factory refurbished Page 9 GDS 78XP Operation amp Maintenance Manual Revision 2 0 SELECTING A LOCATION Install the GDS 78XP in a suitable location as close as possible to the point of intended sample
19. ammed into the controller s channel configuration Controller Showing MODBUS COMM ERROR Check for incorrect MODBUS polarity swap A and B if unsure no damage will occur Page 22 GDS 78XP Operation amp Maintenance Manual Revision 2 0 e Verify that MODBUS master is requesting data from correct MODBUS address e Verify that MODBUS master is requesting data from register 31002 e Verify that there are no other MODBUS slave devices with identical MODBUS address GDS 78XP Display Blank e Verify DC power at 10 Power Supply board TB2 terminals 1 24 and 4 e Verify ribbon cable connected between IO Power Supply board and Display Assembly Page 23 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Model Power Input Display Sensor Types Sample Conditioning Accuracy Standard Output Temperature operating Temperature inert Memory Materials Dimensions Approvals Warranty GDS 78XP Process Monitor for Low Oxygen Applications 24VDC 596 at lt 10 watts High resolution color LCD with engineering units bargraph and 30 minute trend Electrochemical sensors for toxic gases infrared sensors for combustibles or CO2 Sample conditioning option 1 1 0 psig to 50 psig inlet pressure must remain constant with 10 of nominal value 0 1 micron coalescing filter with high quality glass flow meter Sample conditioning option 2 10 psig to 3000 psig stainles
20. anty on sensors GDS Corp reserves the right to void warranty claims based on evidence of misuse abuse or misapplication Warranty period starts on date of shipment IF YOU HAVE QUESTIONS GDS Corp 2513 FM 646 Road North Santa Fe Texas 77510 409 927 2980 Office 409 927 4180 Fax info gdscorp com www gdscorp com Page 6 GDS 78XP Operation amp Maintenance Manual Revision 2 0 INTRODUCTION Thank you for choosing the GDS Corp GDS 78XP 0 o Process Gas Monitor for Hazardous Area Applications The GDS 78XP Process Gas Monitor is designed to provide continuous monitoring for gas ims sample streams that are compatible with standard n electrochemical infrared and photoionization sensors The GDS 78XP combines the industry proven reliability and performance of GDS Corp T pie b m GASMAX gas monitors with high quality sample ba NI T conditioning and flow measurement components Filter Drain to deliver cost effective solutions for process os monitoring applications o The GDS 78XP is designed to operate with samples from pressurized sources between 1 psig and 3000 psig depending on sample conditioning hardware EXPLOSION PROOF INSTALLATIO
21. are subject to accelerated degradation and may demonstrate a permanent loss of sensitivity Value shows 2596 of scale indicates SENSOR FAULT from GASMAX monitor Value shows 105 of scale indicates an OVERRANGE condition where the sample gas caused the sensor to read more than 10096 of scale Sensor Fails Calibration Sensor reading during zero calibration exceeds upper limit of zero sensor is defective and should be replaced Sensor reading during span calibration too low sensor may be defective However it may be possible to temporarily continue operation by increasing PREAMP GAIN GDS 78XP and Receiving Device Displayed Values Don t Match Check that zero and full scale range values match between GDS 78XP and receiving device controller Use DIAGNOSTICS menu to force the OUTPUT channel Ch2 to 12mA and verify half scale reading on remote controller Check for high impedance shorts to ground on 4 20mA wiring If 4 20mA output is off scale low or high and cannot be adjusted using DIAGNOSTICS mode 10 Power Supply board may be defective and should be replaced Controller MODBUS Data Incorrect Verify that MODBUS master is requesting data from correct data register 31002 Verify that controller MIN and MAX count settings are correct MIN counts should be 800 which corresponds to 4mA and MAX counts should be 4000 which corresponds to 20 mA Verify that the GDS 78XP MODBUS address matches the address progr
22. d level polarity on off delays and other alarm related settings NOTE ALARM SETTINGS ONLY AFFECT THE GASMAX LCD DISPLAY COLOR IF LOCAL RELAYS ARE NOT INSTALLED LOCAL ALARM SETTINGS WILL HAVE NO EFFECT ON ALARM SETTINGS AT ANY REMOTE DEVICE THAT MONITORS THE GDS 78XP 4 20MA OUTPUT Page 17 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Calibration is critically important to ensure correct operation of the GDS 78XP The built in CAL MODE function is designed to make calibration quick easy and error free a successful ZERO and SPAN calibration requires only four keystrokes During CAL MODE zero and span the sensor output is disconnected and the GDS 78XP transmits a fixed mA value called the CAL MARKER to notify the receiving device that a calibration is in progress During the following CAL PURGE DELAY time the GDS 78XP transmits a fixed 4 0 mA signal to prevent external alarms during calibration In the case of Oxygen sensors during CAL PURGE DELAY the output simulates a typical atmospheric reading of 20 896 CAL MODE automatically exits if no keystrokes are detected after 5 minutes Follow these GDS 78XP calibration guidelines Calibration accuracy is only as good as the calibration gas accuracy GDS Corp calibration gases are traceable to NIST National Institute of Standards and Technology e Never use calibration gas that has passed its expiration date e Check the SPAN GAS VALUE setting and make sure it
23. er wiring via NPT fitting on bottom of junction box enclosure cutout not provided Thermostat ACHOT Black Red White Green AC NEUTRAL gt AC GND Heater Element Figure 4 5 200W AC Heater Wiring Local codes and good wiring practice require an AC shutoff switch within sight of the heater assembly for maintenance and testing IMPORTANT Keep all electrical fittings tight while circuits are alive SAMPLE INLET Attach a length of tubing to the Sample Inlet using the supplied compression fitting The GDS 78XP uses a variable area flow meter or high pressure regulator to monitor and control sample flow For option 1 inlet pressure must be maintained between 1 0 psig and 50 psig and must remain within 10 of the nominal value Excessive changes in sample inlet pressure will proportionally change the sample flow rate rates below or above the desired 0 5 liter per minute rate may cause incorrect readings If the optional low flow switch is included flow rates Page 13 GDS 78XP Operation amp Maintenance Manual Revision 2 0 below the desired value will cause the FAULT relay to activate if installed Options 2 and 3 employ a high pressure regulator and maintain a fixed flow rate over a wide range of inlet pressures FILTER DRAIN amp FILTER BYPASS All GDS 78XP configurations include a coalescing filter with stainless steel drain valve The drain valve should be opened periodic
24. ess 2000 0147 Filter Element 2000 0140 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Display Run Cal Valve Cal Gas Inlet Run Cal Valve Sample Flow Meter 1200 0037 10 0387 I O Board 10 0390 Optional Relays amp MB 10 0388 Sensor Head 10 0247 Sensor 10 98xx Smart Sensor Sample Outlet Flow Cell 10 0205 Regulator 1200 0043 Pressure Gauge 1200 0044 Flow Meter 1200 0451 Flow Switch 1200 0224 Figure 12 3 Sample Conditioning Option 2 with Flow Switch Spare parts Page 42 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Display 10 0387 1 O Board 10 0390 Optional Relays amp MB Flex 10 0388 Tubing N Sensor Head N A Sensor GDS IR Run Cal O specify gas Valve Sensor Flow Cell Sample Outlet 10 027 1 Sample Flow Meter Cal Gas Inlet Filter Drain Regulator 1200 0043 Pressure Gauge 1200 0044 Filter Stainless Run Cal Valve Flow Meter 2000 0147 1200 0037 1200 0451 Flow Switch Filter Element 1200 0224 2000 0140 Figure 12 4 Sample Conditioning Option 2 with Flow Switch amp GDS IR Spare parts Page 43 GDS 78XP Operation amp Maintenance Ma
25. hazardous area must comply with all applicable restrictions requirements and guidelines for said hazardous areas It is the end user customer s final decision to ensure that the GDS 78XP is suitable for the intended use e GDS 78XP is designed and constructed to measure the level of certain gases in backgrounds that contain free oxygen Accuracy in atmospheres containing steam or inert gases cannot be guaranteed e Do not paint enclosure transmitter or sensor assembly e not operate the GDS 78XP if its enclosure is damaged or cracked or has missing components Make sure the cover internal PCB s and field wiring are securely in place before applying power e Do not expose the GDS 78XP to electrical shock or continuous severe mechanical shock Protect the GDS 78XP from dripping liquids and high power sprays e Calibrate with known target gas at start up and check on a regular schedule at least every 90 days More frequent inspections are encouraged to spot problems such as dirt oil paint grease or other foreign materials in the sample tubing or in the sensor head Periodically test for correct operation of the system s alarm events by exposing the sample extraction point to a calibration gas concentration above the High Alarm set point e Use only for applications described within this manual WARRANTY GDS Corp UPS products carry a 2 year limited repair or replacement warranty on electronics and workmanship and one year warr
26. he remaining sensitivity Sensor Life is not necessarily linear and a rapid reduction in the senor life reading can be due to temperature extremes high levels of target gas the presence of certain gases that poison toxic sensors and other environmental factors Always check the flow meter for the presence of moisture In the event that moisture or liquid is drawn in the GDS 78XP the entire unit should be disassembled and cleaned In some cases the flow meter or flow switch may need to be replaced If liquid is drawn into the GDS 78XP always inspect the sensor for signs of damage FAULT AND OVERRANGE CONDITIONS The GASMAX CX gas detector continuously monitors the sensor for fault or overrange conditions The fault setting is user adjustable and is typically set for 596 to 1096 of scale default Electrochemical sensors that show fault are defective and should be replaced Bridge type sensors such as catalytic bead or PID sensors allow the zero value to be adjusted and can often be rebalanced to normal operation However if this happens regularly then the sensor may be defective or the gas stream may contain one or more compounds that affect the sensor In the event of an overrange condition the 4 20mA output will exceed 20mA and the display will indicate OVERRANGE or FAULT Page 20 GDS 78XP Operation amp Maintenance Manual Hevision 2 0 SENSOR REPLACEMENT If a sensor shows FAULT does not respond to gas or can no lo
27. it value from A D converter Page 32 GDS 78XP Operation amp Maintenance Manual Revision 2 0 FR State 32023 4 N A True if fault relay active Page 33 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Ch 2 Marker Flag 33058 4 N A True if marker active Ch 2 Linearize 33059 4 N A True if linearization table active Ch 2 Err Flashing 33060 4 N A True if channel error Page 34 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Modbus TCP Timeout 40081 3 N A MODBUS TCP timeout mSec Modbus TCP Poll Delay 40082 3 N A MODBUS TCP poll delay mSec Page 35 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Ch 1 Cal Zero 42001 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Cal Span 42003 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Zero Value 42005 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Span Value 42007 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Fault Value 42009 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Alarm 1 Setpoint 42011 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Alarm 2 Setpoint 42013 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Alarm 3 Setpoint 42015 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Manual Gain 42017 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 1 Manual Offset 42019 3 N A Modbus 32 bit IEEE 754 Floating Pt Ch 2 Cal Zero Value 4
28. la 40 0 0 0 0 0 0 0 0 ba ba ba ba ba ba ba ba Configure Hydrogen Sulfide E Units 25 Zero 0 00 Span 100 0 Decimal Points 0 Channel on Yes Deadband 0 00 Backup Restore Calibrate Offset db Gain 1 00 Cal Zero 0 00 Cal Span 100 0 Set Unity Gain gt Figure 10 4 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Temperature Compensation compensates for changes in sensor output gain and zero value offset as sensor temperature changes Individual values for gain and offset can be entered for eleven points ranging from minus 406 to 60C Gain and offset values are linearly interpolated between points by the internal microprocessor NOTE These values are typically set by the sensor manufacturer and should not be changed Configure Menu Measurement Name User programmable character string to describe the channel Otherwise called tag name E Units User programmable character string that describes the engineering units value Zero Channel zero value typically 0 Span Channel full scale value Max value is 9999 Decimal Points Determines the number of displayed digits to the right of the decimal point Channel On Channel ON or OFF setting An OFF channel will have no effect on any alarm or output value Deadband The value around zero for which the screen will show 0 0 Eliminates display of small values around zero d
29. lance of this manual the term press will be used to describe activation of any key via the magnetic wand Below the LCD display two LEDs monitor the MODBUS RS 485 or Ethernet network interface Flashing indicates sent or received DN CAL EDIT data Pressing the NEXT key momentarily causes the GDS 78XP display to sequence display and trend screens The Display Screen shown shows the calibrated engineering units analog bar graph tag measurement name and engineering units ppm The Trend Screen displays a graph that shows the most recent 30 minutes of data as well as alarm levels Pressing the DOWN CAL key followed by the EDIT key initiates Calibration Mode For a detailed description of calibration see Chapter 6 Pressing the EDIT key activates the USER MENU mode See Chapter 9 During USER MENU mode the UP DN and NEXT keys are used to select and confirm menu entries The USER MENU allows the operator to view the Event Log and channel parameters and change system settings such as alarm levels and real time clock day and date Page 16 GDS 78XP Operation amp Maintenance Manual Hevision 2 0 Figure 5 1 GDS 78XP GASMAX Display Sequence Display Screen amp Trend Screen ALARM SETUP Using a magnetic wand select the GASMAX Main Menu by placing the magnet next to the EDIT switch located on the lower right side of the GASMAX II display Select Channel 1 and then ALARMS to adjust the desire
30. matches the calibration gas See Fig 6 2 e Always use a GDS Corp calibration cup that completely surrounds the sensor head e Be sure to use ZERO AIR a mixture of 21 oxygen and 79 nitrogen as a zero reference unless you are certain that no target gas exists in the area Ambient gas may result in an elevated zero condition that will cause a FAULT to occur once the ambient gas is no longer present e Always calibrate a new sensor before depending on the device for personnel or equipment safety e Calibrate on a regular schedule GDS Corp recommends a full calibration every 3 months with periodic bump tests on a more frequent basis to ensure that the sensor has not been affected by temperature extremes or the presence of incompatible gases CALIBRATION PROCEDURE Before beginning calibration make sure you have the following items A cylinder of calibration gas fixed flow regulator and a length of flexible tubing A cylinder of zero air may be necessary if the absence of target gas cannot be confirmed in the sample area To calibrate a GDS 78XP sample draw 1 If using Zero Air set the Run Cal valve to the CAL position pointing to the right and connect the cylinder of zero air to the GDS 78XP calibration port Turn on the regulator and verify flow on the flow meter Otherwise allow the current sample to continue to flow into the GDS 78XP 2 Press the DOWN CAL key and within 5 seconds press the EDIT key to enter CAL MODE Page 18
31. n be used to acknowledge an Alarm 2 relay contact closure Wiring from any remote pushbutton to TB3 should be shielded and protected from noise spikes to prevent false Alarm Reset commands WARNING RELAY CONTACTS ARE RATED FOR RESISTIVE LOADS ONLY INDUCTIVE LOADS MAY CAUSE ARCING WHICH SHORTENS LIFE AND MAY INTERFERE WITH SENSOR DATA MODBUS CONNECTIONS OPTIONAL The dual optional GDS 78XP MODBUS RTU interface allows remote controllers or PLCs to monitor most aspects of operation including real time data range and alarm setpoints and alarm and fault status bits The GDS 78XP interface supports 9600 Baud RS 485 differential signaling only Access to each MODBUS RS 485 interface is via TB2 on the optional Relay MODBUS board mounted on the back of the GASMAX CX display module MODBUS system architecture requires that the devices in any MODBUS loop be connected in a daisy chain layout This minimizes signal reflections and improves signal noise margin A MODBUS Termination Jumper installs a load resistor across the MODBUS signal lines and should only be set to A ON at the last device in the string Cable selection for MODBUS systems is important for both signal integrity and power distribution For MODBUS data signals GDS lt o 2 5 Corp recommends 20GA to 24GA twisted shielded cable Daisy chain power distribution may require larger gauge wire since it is critical that the s
32. nger be calibrated it should be replaced Use type 10 98XX Ryyyy sensors where the XX is gas type Fig 3 Page 21 1 and yyyy is range 25 0025 Step 1 Turn off DC power Step 2 Disconnect the sample inlet tube at the sensor flow cell Step 3 Disconnect the sample exhaust tube at the flow cell Step 4 Unscrew the sensor flow cell and sensor head cover Step 5 Pull straight down to remove the existing sensor Step 6 Compare the new sensor with the old sensor and verify identical part numbers Step 7 Install the new sensor by aligning the arrow on the sensor with the arrow on the sensor head and pushing straight up Step 8 Reassemble the sensor head cover and flow cell and reattach the sample inlet and outlet tubing Step 9 Apply power allow the sensor to warm up for several hours Step 10 Perform a complete calibration GDS 78XP Operation amp Maintenance Manual Revision 2 0 Fault Indication on Output Channel Fault or Overrange on power up Certain toxic sensors indicate off scale low or high at power up and quickly drift towards zero This is normal behavior Continuous Fault indication Remove sensor and examine for moisture or discoloration Replace sensor if wet or discolored Fault indication generally indicates sensor useful life is exhausted Sensors left unpowered for more than 3 months
33. nual Revision 2 0 Display 10 0387 1 O Board 10 0390 Optional Relays amp MB 10 0388 Sensor Head 10 0247 Sensor Sample Outlet 10 98xx Smart Sensor Flow Cell 10 0205 Cal Gas Inlet Sample Flow Meter Regulator l 1200 0043 Pressure Gauge Filter Drain Filter Bypass 1200 0044 Filter Combination Run Cal Valve Flow Meter 1200 0167 1200 0037 1200 0451 Filter Element Kit 1200 0169 Figure 12 5 Sample Conditioning Option 3 with Flow Switch Spare parts Page 44 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Display 10 0387 I O Board 10 0390 Optional Relays amp MB 10 0388 Sensor Head N A Sensor GDS IR specify gas Sensor Flow Cell Sample Outlet 10 0271 Cal Gas Inlet
34. p 24 5 degc Analog Inputs Menu 57 Shows current input readings for channel 1 and channel 2 Counts 0 Current 0 00mA Analog Outputs Analog Outputs Menu 4 20mA outil Oma Shows the live output values on analog channel 1 and analog channel 2 4 20mA Out2 OmA Also shows the feedback monitor reading for both channels 0 1 Fdbk 0 07 Out2 Fdbk 0 06 LED Test Menu LED Test Cycles the external LED Comm Test Comm Test Menu Connect Loopback Performs a loopback test to verify proper operation of the serial Pont ds GE Bad components Only available if optional Relay Modbus board is installed Port 2 gt 1 Bad 420 0 1 Fdbk 1 ADC Readings 420 Out2 Fdbk 2 Displays values monitored by internal analog to digital converters Sensor V SensrAmp PSU Figure 10 7 Diagnostics Menu Tree Page 31 GDS 78XP Operation amp Maintenance Manual Revision 2 0 The GDS 78XP features a full complement of user accessible MODBUS registers that can provide a complete snapshot of the gas detector configuration This includes all real time data preset zero span and calibration values and user programmable text Variable Name Alias Read Write Notes Ch 1 Analog Output Raw 31001 4 N A 12 bit value 800 4mA 4000 20mA Ch 2 Analog Output Raw 31002 4 N A 12 bit value 800 4mA 4000 20mA Ch 1 A2D Raw Counts 31003 4 N A 12 bit value from A D converter Ch 2 A2D Raw Counts 31004 4 N A 12 b
35. put include unit name time and date warm up and calibration delay View Event Log Clear Event Log view Sensor Life settings and Event Log Diagnostics J Relays Diagnostics Menu comprehensive set of tools that can be used to Analog Inputs M EE activate relays simulate output values and test serial ports Serial Ports ADC Readings Figure 10 1 Main Menu Tree Page 25 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Alarm OUTPUTS Menu The Alarm Outputs Menu controls the four optional alarm relays if installed These setting include relay programming acknowledge failsafe mode and specific input override options NOTE The Alarm Modbus board containing the 3x alarm relays and 1x fault relay is optional on the GDS 78XP Alarm Outputs Relay 1 Relay 2 Relay 3 All three relay outputs are identical and can be set to respond to channel 1 or channel 2 events The fault relay is always dedicated to Relay x Alarm 1 Alarm 2 Alarm 3 channels can activate the relay Options are Off Ch1 Ch2 Ch1 and Fault n P chy Acknowledge Ch2 and Ch1 or Ch2 Alarm 1 2 3 and Fault Determines which channel or combination of Failsafe Acknowledge Determines if the alarm can be reset by an Acknowledge Override command YES or not NO Failsafe Determines if the relay is OFF when inactive NO or ON when inactive YES Failsafe connections thru the Normally
36. r the serial port Byte Order sets the byte order for words larger than 16 bits Enable LEDs If YES front panel LEDs indicate MODBUS transmission MODBUS TCP Menu Slave Settings Byte Order sets the byte order for words larger than 16 bits Master Settings Timeout Length of time mSec that master will wait for a reply before indicating a comm timeout Poll Delay Length of time in mSec between sequential read requests Enable LEDs if YES front panel LEDs indicate MODBUS TCP transmission Network Settings Menu DHCP Enabled If YES uses a remote DHCP server to establish a network address If NO uses fixed address Hostname Character string that defines device network name IP Address Network address If DHCP enabled will show address assigned by DHCP server If DHCP disabled is IP address programmed by user Net mask Network mask value See above Gateway Network gateway value See above Troubleshooting Menu View Error Count View a menu that tracks the number of network errors Clear Error Count Resets number of network errors to zero Figure 10 5 Comm Settings Menu Page 29 GDS 78XP Operation amp Maintenance Manual Revision 2 0 System Settings Menu The Comm Settings Menu allows the user to configure the Ethernet interface MODBUS TCP slave and two optional RS 485 serial interfaces System Configure Menu Version v1 00 Configure ES Date amp
37. rve maximum inlet length recommendations e Always provide an independent sample exhaust line e sure that exhaust gas is directed away from personnel and vented to a safe area where exhaust gas can dissipate e f mounting the unit outdoors protect all exposed vents or intakes with screens or filters to keep insects moisture or dirt from entering the device Page 15 GDS 78XP Operation amp Maintenance Manual Revision 2 0 FLOW SETUP Once hardware installation is completed apply power to the GDS 78XP and verify that the GASMAX display is operational Open the inlet valve and adjust the flow meter for approximately scale or about 0 5 liters per minute If the flow meter does not indicate proper flow check the inlet tubing for restrictions or blockage If full scale flow cannot be obtained check the sample outlet tubing for blockage See Table 1 for recommended flow meter settings for gases of different density To check the Low Flow switch if installed set the Run Cal valve to the CAL position After ten seconds the display should flash RED and the message FAULT should appear GASMAX CX DISPLAY UP RST NEXT There are four magnetic switches on the face of the GASMAX CX arranged in a quadrant around the LCD display Starting in the upper left and proceeding clockwise these are labeled UP NEXT EDIT and DN CAL To activate or press a magnetic switch swipe the magnet near the switch For the ba
38. s steel filter with 0 1 micron coalescing element and high pressure regulator Sample conditioning option 3 10 to 1500 psig stainless steel combination coalescing and membrane filter with 0 1 micron coalescing element and high pressure regulator 596 of full scale typical Three wire 4 20mA current source outputs with fault and overrange indication Maximum loop resistance is 750 ohms with standard 24VDC supply Ethernet RJ 45 with built in MODBUS TCP interface and web server Optional Relay MODBUS interface with 3x 5A SPDT programmable alarm relays 0 to 50 standard no enclosure 20 C to 50 C with NEMA 4X enclosure and optional 200W AC heater Heater thermostat is set to 50 F and is not user adjustable 20 C to 55 C In cold weather GDS Corp recommends turning on the AC heater if installed for several hours before applying DC power On board non volatile memory retains all user settings Instrument housings Aluminum Tubing amp fittings 316 stainless steel Painted steel plate 12 8 x 14 8 x 8 NEMA 4x non metallic enclosure 24 x 24 x 8 GASMAX CX Gas Monitor CSA Certified Class Div 1 amp 2 Groups B C D Sequencer enclosure CSA certified for use in Class Div 1 areas Flame arrestors UL certified for use in Class 1 Div 1 areas Two years on electronics Page 24 GDS 78XP Operation amp Maintenance Manual Hevision 2 0 The GASMAX CX gas monitor used in
39. ue to sensor drift Calibrate Menu Offset Shows the computed offset value based on the latest calibration Gain Shows the computed gain value based on the latest calibration Cal Zero The value for the zero point calibration Cal Span The value for span calibration typically 50 of full scale Set Unity Gain Clears gain and offset to 1 00 and 0 00 respectively WARNING Set Unity Gain resets calibration data Channel Settings Menu Tree 2 Page 28 GDS 78XP Operation amp Maintenance Manual Revision 2 0 Comm Settings Menu The Comm Settings Menu allows the user to configure the Ethernet interface MODBUS TCP slave and two optional RS 485 serial interfaces Comm Settings COMM 1 Settings COMM 2 Settings ModbusTCP Network Settings Troubleshooting COMMx Settings Modbus Slave BaudRate 9600 Parity None Slave ID 42 Byte Order BADC Enable LEDs Yes ModbusTCP Slave Byte Order 8406 Master Timeout ms 500 Poll Dly ms 250 Enable LEDs Yes Network Settings DHCP Enabled Yes Hostname Uni t 44 1000 Ip Address 169 254 100 10 Netmask 254 254 0 0 Troubleshooting View Error Count Clear Error Count Comm X Menu both comm port setting menus are identical Type Modbus Slave determines whether the MODBUS port is a master or slave Baud Rate Sets the baud rate for the serial port Options are 9600 19200 38400 57600 and 115200 baud Slave ID Sets the MODBUS slave ID fo
40. upply voltage for the GDS 78XP at the far end of the string not fall below 20VDC during power up Note that while the GDS 78XP has two sets of wiring terminals for MODBUS A and B signals daisy chain power wiring requires that two wires be installed in the 24 and GND terminals on the GDS 78XP I O Power Supply board This can be difficult Figure 4 4 MODBUS Wiring if wire sizes are larger than 18 For these reasons if MODBUS is Junction Box required GDS Corp recommends the addition of the MODBUS Wiring Junction Box see Fig 5 7 This option minimizes the need to access wiring inside the GDS 78XP provides individual wire landing points for incoming and outgoing MODBUS and power wiring and shields and makes it easy to temporarily disconnect the GDS 78XP power or MODBUS connections without affecting any other MODBUS device Page 12 GDS 78XP Operation amp Maintenance Manual Revision 2 0 AC HEATER OPTIONAL The 200 watt AC powered heater is recommended for outdoor applications where ambient temperatures may fall below freezing for extended periods of time The heater is available in either 110VAC or 230VAC models Access to the heater wiring is via a separate NPT fitting on the bottom of the heater junction box Note that all high voltage AC wiring must be kept separate from lower voltage DC and signal lines Fixed Thermostat ON below 50 10 Heater Element Access to heat
41. vent clears NO clears the alarm automatically Trip On HIGH causes the alarm to activate if the value goes above the Alarm x Setpoint 20 00 Latching NO Trip On High setpoint Trip On LOW activates the alarm if the value goes below the setpoint Fault off On Off Delay adjusts the time delay between the time when the event Delay sec 0 Off Delay min 0 Dead Band L occurs and when the alarm is activated Deadband prevents alarm cycling when the value is close to the alarm level Fault Alarm Setpoint 10 00 Fault Alarm setpoint is typically set at 10 of full scale Data From Data From Menu EC Sensor Remote Sensor No Min Raw 800 Max Raw 4000 Filter Samples 20 Polarity POS PGA Gain gt Heater Enabled No Heat degC 10 0 Data From determines the source of the data for this channel Min Raw Max Raw Set the range of the input A D converter Normally set to 800 min and 4000 max Useful if a sensor s output does not provide a full range signal Filter Samples Number of samples used by the smoothing filter PGA Gain sets the analog amplification level in the smart sensor interface circuit WARNING Changing PGA gain resets calibration data Heater Enabled Determines if the internal sensor heater is ON or OFF Heat degC Heater thermostat setting Figure 10 3 Channel Settings Menu Tree 1 Page 27 Temp Gain Offset 40 1 40 i
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