AMT Dewpoint Transmitter Instruction Manual
Contents
1. 5 pA Better than 0 3 C dewpoint 20 C to 60 C 20 C to 70 C From 1kPa 0 01 barA to Maximum 35 000kPa 350 barA Maximum 95 RH Non condensing Independent but ideally 2 to 5 litres per minute Max 25 litres min IP66 NEMAAX rated size C DIN EN 175301 connector at the transmitter and other end terminated with bootlace ferrules Supplied with 2m standard cable Nominal diameter 3 4mm 92ohms km EMC Immunity Complies with EN 61000 6 1 2001 Emissions Complies with EN 61000 6 3 2001 10 seconds Sensor Open Circuit Output drives to 20 50mA Sensor Short Circuit Output drives to 20 75mA Sensing Element connected to the 4 20mA loop but isolated from body 316 Stainless steel body with size C DIN EN 175301 connector 316 Sintered stainless steel filter 50 micron 316 Stainless Steel IP66 NEMA4X when Connector mated to Transmitter 3 4 UNF 16tpi with integral Viton O ring seal 24 months in case of faulty workmanship and defective parts 12 months subject to usage 175grams includes connector Page 8 7 Appendix A AMT with Connector General Arrangement 0 625 dia 15 99 Process thread 74 x 16 UNF O Ring seal 30mm A F 1 185 A F Page 9 8 Appendix B Transmitter Holder General Arrangement S20 ep GC 1 Ore SZL Z vs SBungy OZIS 46u1o amp JOJ KIEN Sum eqni BY ssoJ3e uorsueuilp OU Sum egni ao GIL YUM U2. AMT Dewpoint Transmitter Instruction Manual Alpha Moisture Systems Alpha House 96 City Road Bradford BD8 SES England Tel 44 1274 733100 Fax 44 1274 733200 email mail amsytems co uk web www amsystems co uk AMT Dewpoint Transmitter Instruction Manual Issue4 07 03 2011 1527 AMT User Manual Q N A n LI Index BA e TE Ee Gas Compatibilities tette eR TER TUR ad UN 1 Installing the AMT in a Air Gas Sampling System c aasta an on e eere eee 2 Piping installation eee E eo tod en d t Ee dt e a EE a 2 Component Itidex eR Rat ME AS T ete e edat e nee Wise 3 Installing and Commissioning the Model AMT Transmtter eese 3 Winne the EE 4 Connector Pins DE 4 Normal Operation ehe 3 1 Analogue 4 20mA Mode 2 wire esses ener enne aa naa Kaa Ka ana eene nennen 5 ATMOCAL p I TI ETE I Pre conditioning the transmitter ccseessesssnssensnesnennennnennennennnennsnnnnnnennsnnnnenensnnennennennee nen enne 5 Entering Autocal Mode a n a a ene nennen Ea EKA NEEN ne nene nene nenne 6 ee E E EE 6 Completing the autocal 5 epe ree pet pio pe lt e piae n Od 6 AMT Range AutoCal Method Lookup Table 6 El OH Div e OC AMT Se Cali Cat Onn mammaa Sakano nennen Appendix A AMT with Connector General Arrangement esee H Appendix B Transmitter Holder General Arrangement sss
3. Sulphur hexaflouride SF has no effect on the sensor If the gas has been exposed to arcing however it is possible that various acidic species will have been formed that will corrode the sensor When testing SF that may have been arced therefore an acidity test should be carried out first if the gas proves to be acidic then the moisture test should not be carried out Itis strongly recommended that the sample should not contain particulate matter oil or other heavy hydrocarbon condensate If these components contaminate the sample system and or the measuring sensor the system response time will be lengthened although the sensor calibration will not be effected Page 1 2 Installing the AMT in a Air Gas Sampling System The piping installation schematic diagram see section 2 1 shows all components which could be used in a dry gas measurement application although not all the items shown will be required for every installation The flow rate although not critical to the sensor measurement should be low enough to avoid abrasion to the sensor surface without being so low as to extend the system response time to an unacceptable level In general a flow rate of between 2 and 3 litres min at NTP will give the right balance The sensor is a variable capacitor which is directly affected by changes in partial pressure of water vapour These changes are proportional to the dew frost point temperature Partial pressure of water vapour i
4. 10 1 1 Overview The Model AMT Dewpoint Hygrometer is a 2 wire 4 20mA loop powered transmitter used for continuous measurement of moisture in a process gas or compressed air The Model AMT transmitter can be factory configured to output a 4 20mA linear signal for any of the following moisture units C or F dewpoint ppm v ppb v g m3 and Ib MMSCF The ultra high capacitance sensing element is long lasting and offers excellent sensitivity repeatability and response speed Each unit is calibrated traceable to International Humidity Standards and is supplied with a Certificate of Calibration guaranteeing accuracy to 2 C dew point The transmitter also incorporates an Automatic Calibration AUTOCAL feature which allows the user to carry out field calibration span check The AUTOCAL feature is operated by means of two small buttons built into the transmitter body To avoid accidental corruption the buttons are locked in normal operation and can only be activated by following a specific routine The RISC microprocessor circuitry of the Model AMT transmitter allows high resolution with advanced self diagnostics for fault conditions It also enables periodic re calibration of the moisture sensor storing calibration data within the fully self contained unit Loop powered by a 7v to 28v dc source The Model AMT transmitter will provide the user with a linear 4 20mA signal over the chosen range The mechanics of the Model AMT tra
5. F and 20 C 4 F top end range AMT transmitters When the AMT sensing element is exposed to a dewpoint level above the top end range of the transmitter the sensor will saturate and the transmitter can be AutoCaled to 0 C or 20 C For both 0 C and 20 C AMTs ambient dewpoint is usually adequate to saturate the sensor Method 3 Set against Ambient moisture level Only applicable to 20 C 68 F top end range AMT transmitters When the ambient dewpoint is known then the AMT can be AutoCaled to the ambient value Page 5 4 1 4 2 4 3 4 4 Entering Autocal Mode Once the transmitter has been pre conditioned the AutoCal Mode of the AMT can be activated Press and hold the W and D buttons simultaneously for 5 seconds ONLY PRESS THE BUTTONS IF THE SENSOR IS PROPERLY PRE CONDITIONED FAILURE TO COMPLY WILL CORRUPT THE TRANSMITTERS CALIBRATION The attached 4 20mA display will after the 5 seconds indicate the bottom range of the AMT or 4mA if reading current for 5 seconds confirming that autocal mode has been entered The buttons should be released once the display indicates the bottom range After the 5 seconds delay the AMT will revert to the measured dewpoint and the buttons will be active Adjust the autocal Use the W and D buttons to move the reading up or down so that the desired dewpoint is displayed Method 1 Adjust the AMT reading until the indicator reads the known moisture
6. This item is required when the sampling is to be intermittent When installed it prevents the ingress of wet air to the sample system while the sample is not flowing improving the response time 9 Flow Control Valve This can be a separate item or combined with the flow indicator 10 Flow Indicator The recommended sample flow is 2 to 3 SL M 11 Sample Exhaust The exhaust can be vented to atmosphere or returned to the process line as discussed above Installing and Commissioning the Model AMT Transmitter It is advisable to carry out an initial purge routine of the sample loop before installing the transmitter in order to remove the possibility of sensor damage on start up Refer to the sample system schematic in section 2 1 Open the inlet isolation valve slowly until a small flow of air gas at atmospheric pressure flows through the inlet pipe work to the transmitter holder and exhausts through the sensor entry port of the transmitter holder Allow this purge to continue for about 15 to 20 minutes to remove any residual moisture from the sample pipe work and components Close the inlet isolation valve and install the transmitter into the transmitter holder Locate and secure the four pin transmitter cable connector in positioned on the transmitter Use the locking screw in order to affect a weatherproof seal Open the inlet valve slowly again and by opening all valves after the transmitter holder allow a low pressure p
7. level Method 2 Adjust the AMT reading until the indicator reads 0 C or 20 C whichever is applicable to the AMT being AutoCaled Method 3 Adjust the AMT reading until the indicator reads the known ambient moisture reading Completing the autocal Once the desired value is reached the autocal process can be completed simply by leaving the buttons untouched for 30 seconds After the 30 seconds the display will indicate the bottom of the range for a period of 5 seconds and then the AMT will exit the autocal mode The AMT will now output the corrected dewpoint and can be reinserted into the process A graphical description of the autocal modes is given on the next page AMT Range AutoCal Method Lookup Table Use the table below to decide which AutoCal methods are appropriate for your AMT Range Methods Appropriate 80 to 20 C 112 F to 4 F 1 amp 2 110 to 20 C 166 F to 4 F 1 amp 2 120 to 20 C 184 F to 4 F 1 amp 2 65 to 0 C 85 F to 32 F 1 amp 2 80 to 0 C 112 F to 32 F 1 amp 2 100 to 0 C 148 F to 32 F 1 amp 2 65 to 20 C 85 F to 68 F 1 amp 3 100 to 20 C 148 F to 68 F 1 amp 3 120 to 20 C 184 F to 68 F 1 amp 3 1 1000ppm v 0 1 100ppm v 0 01 10ppm v 1 1 1000ppb v 1 0 01 10g m3 0 001to1g m3 l 0 1 10Ib MMSCF 0 1 251bD MMSCF 0 1 50lb MMSCF l Page 6 uopeledop IWON 9 uopeoipul s e2ojny aart oaJnpeoolg 1snfpw e e2o0jny LI CT HT uoje
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9. nsmitter have been designed to cope with extreme environmental conditions The rugged stainless steel construction offers protection to IP66 NEMA4X with the transmitter electrical connections made via secure industrial type connector size C DIN EN 175301 The AMT transmitter can withstand 35 000 kPa 350bar maximum pressure and by employing low resistance cable the transmitter can be located at significant distances in excess of 1000 meters from the data collection point Designed with the operator in mind for reliable and accurate measurements the Model AMT is extremely easy to install and operate requiring little or no maintenance Gas Compatibilities The Model AMT sensing elements are Al O and therefore suitable for many different industrial and research applications Most gases can be checked for their moisture content with no need for the calibration to be altered when changing between different gases as the sensor operates only with reference to the water vapour content However some gases must be avoided as they are not compatible with the material used in the construction of the sensor Ammonia NH3 and chlorine Cl must be avoided at all times even in small quantities Hydrogen chloride HC also attacks the sensors very quickly Some less aggressive acidic gases such as sulphur dioxide SO2 can be monitored as long as the moisture content is low generally less than 100ppm v If in doubt please ask your supplier
10. s directly affected by total pressure and this being the case the instrument will display the dew frost point temperature at whatever total pressure the sensor is exposed therefore care should be taken to ensure that the sample pressure at the sensor is that at which the dew frost point readings are required The measuring transmitter can be installed directly into the process line but this does create problems with access for maintenance and calibration It is for these reasons that we recommend that the transmitter be installed in a bypass fast loop or total loss sample system where the transmitter is accessible without interrupting the main process flow line 2 1 Piping installation MAIN PROCESS LINE NOTES The sample point should be on the upper surface of a horizontal pipe or ona vertical section of pipe where ever possible The sample tube should run continually upwards from the sample point If this is not possible an inspection port or drain tap should be installed at the lowest point in the system Page 2 2 2 Component Index 2 3 1 Sample Isolation Valve This is a recommended item as it allows access to the sample system without interrupting the main process line 2 Sample Tube This should be stainless steel for dry air or gas applications but copper or carbon steel can be used where wetter gases are to be measured If any section of the sample tube must be flexible then PTFE should be used In most ca
11. ses 3mm OD 1 8 is sufficient as it provides good system response time within minimum flow 6mm OD 1 4 tube can be used where pressure drops across the 3mm tube are too high 3 Filter Unit A filter unit is recommended when the samples are likely to contain particulate matter If the air gas sample contains heavy hydrocarbon condensate the filter must be ofthe coalescing type with a drain The filter unit should be positioned as close to the sample point as practical 4 Pressure Reduction Valve or Pressure Regulator If the sample is to be measured at atmospheric pressure then the valve 4A should be fitted and 4B omitted from the system If the sample is to be measured at full line pressure and the exhaust vented to atmosphere then valve 4B should be fitted and 4A omitted from the system If measurements are to be taken at full line pressure and the sample is to be returned to a part of the main line or a vent which is at a pressure higher than atmospheric and the input to that line needs a controlled pressure then both 4A and 4B will be required 5 Sample Pressure Gauge This is not a critical part of the moisture measurement but may be required if Dew Frost point measurements are to be made at higher than atmospheric pressure 6 Measuring Transmitter see Appendix A AMT with Connector General Arrangement 7 Transmitter Holder see Appendix B Transmitter Holder General Arrangement 8 Desiccant Chamber
12. sipure spuo99s G Joj 13419601 OS M DIOU pue ssalg epopy eso ny Bunejug L indino Page 7 Faults Errors e If the sensor is short circuited the transmitter will produce a constant 20 75mA output e Ifthe sensor is open circuited the transmitter will produce a constant 20 50mA output e fthe hardware develops a fault the transmitter will produce 21 0mA for 5 seconds after switch on and then continue to give an output 6 AMT Specification Display Output Signal Operating Voltage Maximum Series Resistance Sensing element Autocal Factory calibration Accuracy Temperature compensation Resolution Repeatability Operating temperature Storage Temperature Operating Pressure Operating Humidity External Sample Flow Rate Cable Terminations Cable Electromagnetic Compatibility Warm Up Time Fault Conditions Isolation Transmitter Enclosure Sensor Protection Probe Material Wetted Parts Weatherproof Classification Mechnical Connection Mechanical Warranty Calibration Warranty Weight Compatible with the 4 20mA DS1200 Dewpoint Meter 4 to 20mA Linear 7V 28V DC Reverse polarity protected 40 x Supply Voltage 7 Q Ultra High Capacitance Aluminium Oxide Type Field calibration Span check facility Supplied with Certificate of Calibration traceable to NPL NIST 2 C dewpoint NPL NIST traceable for range 90 C to 20 C Temperature compensated for operating range
13. to corruption of the AMTs memory AutoCal allows the user to ensure accuracy to the laboratory calibration by checking the span of the transmitter and correcting for any deviation It should be operated periodically every 2 to 3 months or when verification of the AMT Transmitter is required ACAL adjusts slope of curve Sensor Reading 100 The AMT is supplied with an electronic autocal which allows the calibration span of the transmitter to be adjusted The autocal is controlled by the 2 buttons located on the side of the AMT transmitter labelled W wet and D dry Note The AMT must be connected to an indicator or some device able to supply an accurate measurement of the mA output 4 1 Pre conditioning the transmitter To perform the autocal the transmitter needs to be removed from the process gas at which point the display indicator will read the ambient dewpoint or full scale if the ambient dewpoint level is above the range of the AMT Expose the transmitter to the known autocal moisture level and allow the transmitter to attain equilibrium For technical questions and advice on the time taken to attain equilibrium Contact your AMT supplier Method 1 Expose to a known moisture level Applicable to all versions of AMT Transmitters If a known gas is available within the range of the transmitter then the AMT can be AutoCaled against this value Method 2 Saturating method Only applicable to 0 C 32
14. urge through the whole sample system Note If a closed by pass loop is installed this section of the procedure is not possible Set the required pressures and flows within the sample loop This completes the installation and commissioning but on initial start up it could take several hours for the system to reach equilibrium Page 3 2 4 Wiring the AMT The AMT is a 2 Wire 4 20mA transmitter Typical electrical connection to generate a voltage output is shown below Pin 2 Pin 1 Vs POWER SUPPLY 12V to 28V 4 20mA Signal Vout Voutmax Rs x 20 x 109 Rs Lo la SENSE RESISTOR Note the maximum value for Rs in this circuit can be calculated by the formula Rs max 40 x Vs 7 Q If the wiring resistance is expected to be more than a few percent of the value of Rs then this resistance must be taken away from the answer to get the maximum usable value of Rs 2 5 Connector Pins Red 12 to 28V dc Power Supply Blue 4 20mA Current Return Page 4 3 Normal Operation 3 1 Analogue 4 20mA Mode 2 wire In normal operation the transmitter will produce a 4 20mA signal which is proportional to the level of moisture in the gas being monitored The moisture reading is sampled and up dated once per second The AMT has 3020 distinct steps over the 4 to 20mA range corresponding to a resolution of 0 005mA 4 Autocal Warning Do Not power down during the AutoCal process as this can lead
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