calibration a dew point measurement system

Calibration a dew point measurement system How to calibrate a dew point measurement system? How could we make sure that the reading is correct? By Vahid on 29 June, 2010 11:19 am We have a GE dewpoint measurement equipment installed on the outlet gas pipeline of our plant, I would need to have more information about the ways that we could make sure that the reading is correct. I do appreciate your concern and advice. By CSA on 29 June, 2010 7:31 pm Do you have the instruction manual for the device? Are there any instructions in the manual about verifying calibration/output? These are usually very difficult to calibrate without a lab setup which can flow air of a known humidity over the sensor. I believe the best way is to send the device to a proper calibration lab, unless your site has a very good instrumentation shop/lab. By Sam on 30 June, 2010 8:21 am Hi there, Not much you can do to verify their accuracy in the field I'm afraid. I suggest you take the original datasheet supplied with the analyzer/transmitter and see if there is some calibration constants that you can check. Consult the manual since they might have a calibration validation procedure in there. It will be some constants values you can check on the display or some voltages you can measure on the PCB. Something you can check is the mA outputs according to the factory calibrated zero and span values. If it is dew point you have on the output it should have a facility on the matrix of the transmitter to simulate the 0 to 150 degrees C or whatever your factory calibration should be according to the data sheet. You can then make adjustments on the transmitter's output to make sure the correct Z/S dew point values (as per data sheet)give a accurate 4 to 20 mA output. I know the manufacturer can also supply you with various saturated salt solutions that you can use in a lab or w/shop environment to verify the accuracy of the transmitter so get hold of them and ask them about that. Another possibility is to buy a hot factory calibrated standby identical to the installed unit and just

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5/11/2015 Calibrationadewpointmeasurementsystem

http://control.com/thread/1277824746 1/2

CalibrationadewpointmeasurementsystemHowtocalibrateadewpointmeasurementsystem?Howcouldwemakesurethatthereadingiscorrect?

ByVahidon29June,201011:19am

WehaveaGEdewpointmeasurementequipmentinstalledontheoutletgaspipelineofourplant,Iwouldneedtohavemoreinformationaboutthewaysthatwecouldmakesurethatthereadingiscorrect.Idoappreciateyourconcernandadvice.

ByCSA on29June,20107:31pm

Doyouhavetheinstructionmanualforthedevice?

Arethereanyinstructionsinthemanualaboutverifyingcalibration/output?

Theseareusuallyverydifficulttocalibratewithoutalabsetupwhichcanflowairofaknownhumidityoverthesensor.

Ibelievethebestwayistosendthedevicetoapropercalibrationlab,unlessyoursitehasaverygoodinstrumentationshop/lab.

BySam on30June,20108:21am

Hithere,

NotmuchyoucandotoverifytheiraccuracyinthefieldI'mafraid.Isuggestyoutaketheoriginaldatasheetsuppliedwiththeanalyzer/transmitterandseeifthereissomecalibrationconstantsthatyoucancheck.Consultthemanualsincetheymighthaveacalibrationvalidationprocedureinthere.ItwillbesomeconstantsvaluesyoucancheckonthedisplayorsomevoltagesyoucanmeasureonthePCB.

SomethingyoucancheckisthemAoutputsaccordingtothefactorycalibratedzeroandspanvalues.Ifitisdewpointyouhaveontheoutputitshouldhaveafacilityonthematrixofthetransmittertosimulatethe0to150degreesCorwhateveryourfactorycalibrationshouldbeaccordingtothedatasheet.Youcanthenmakeadjustmentsonthetransmitter'soutputtomakesurethecorrectZ/Sdewpointvalues(asperdatasheet)giveaaccurate4to20mAoutput.

Iknowthemanufacturercanalsosupplyyouwithvarioussaturatedsaltsolutionsthatyoucanuseinalaborw/shopenvironmenttoverifytheaccuracyofthetransmittersogetholdofthemandaskthemaboutthat.

Anotherpossibilityistobuyahotfactorycalibratedstandbyidenticaltotheinstalledunitandjust
5/11/2015 Calibrationadewpointmeasurementsystem

http://control.com/thread/1277824746 2/2

changeitoutwiththisspareonewhileyousendtheotheroneforthecalibrationverificationtothefactoryoneayearoronceeverytwoyears.Theremightbealimitedsensorshelfliveorspecialsensorstoragerequirementsinvolved,sospeaktothesupplierandseeifthismightbepossibleoption.

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