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How to calibrate an ir thermometer, frank liebmann, 2013 05-07


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How to calibrate an ir thermometer, frank liebmann, 2013 05-07

  1. 1. © 2013 Fluke Corporation.Fluke CalibrationWeb Seminar SeriesReal-world expertise and practicaltips about electrical, flow, pressure,RF and temperature calibrationHow to Calibrate anInfrared Thermometer
  2. 2. Today’s Web SeminarHow to Calibrate an IR ThermometerMay 7, 2013How do you know that your infrared calibrations are accurate? Register for this freewebinar from Fluke Calibration to learn how to improve the accuracy of your infraredthermometer calibrations. Topics discussed will include sources of uncertainty,calibration equipment required, overview of the calibration procedure, review of asample uncertainty budget, and recommendations for reporting results.2
  3. 3. Your PresenterFrank Liebmann• B.S. Electrical Engineering University of Utah• 9 years with Fluke/Hart Scientific– Sr. Design Engineer– Radiation Thermometry Engineer• Chairman ASTM Subcommittee E20.02 on Radiation Thermometry• 20 years U.S. Army•• Phone: 801.763.1700 3
  4. 4. What we will be talking about…• Sources of uncertainty• Calibration equipment• Traceability schemes• Laboratory setup• Calibration procedure• Uncertainty analysis• Reporting your results• Questions4
  5. 5. Introduction• IR thermometry calibration can be accurate• Proper procedure must be followed• ASTM E2847, “Standard Practice for Calibration andAccuracy Verification of Wideband InfraredThermometers”5
  6. 6. Sources of Uncertainty• Major– Emissivity estimation of the calibration source– Field-of-view of the infrared thermometer– Temperature gradients on the radiation source– Improper alignment of the infrared thermometer– Calibration temperature of the radiation source– Ambient temperature– Reflected temperature• Minor– Source heat exchange– Atmospheric absorption– Noise– Display Resolution6
  7. 7. Calibration Equipment• Mandatory– Thermal radiation source– Transfer Standard– Ambient Temperature Thermometer– Mounting Device– Distance Measuring Device• Non-mandatory7
  8. 8. Thermal Radiation Source• Calibrated source– Flat Plate– Cavity• Provides thermal radiation8
  9. 9. Thermal Radiation SourceSize of the thermal radiation source• For Fluke IR thermometer models– 5” (~ 125 mm) diameter is enough• Other IR thermometer manufacturers– Consult manufacturer– Testing9
  10. 10. Transfer Standard• Contact Thermometry (Scheme I)– PRT, thermistor, or thermocouple• Non-contact Thermometry (Scheme II)– Radiation thermometer• More discussion under ‘Traceability Schemes’• Implementation– Internal– Third-party laboratory10
  11. 11. Ambient Temperature Thermometer• Monitor laboratory conditions• Use to control uncertainties– Reflected ambient radiation– Ambient temperature11
  12. 12. Mounting Device• Holds IR thermometer• Maintains alignment and measuring distance• May be any of the following– A tripod– A fixture– A hand12
  13. 13. Distance Measuring Device• Used to verify measuring distance• Measuring distance: “Distance or distance range betweenthe radiation thermometer and the target (measuredobject) for which the radiation thermometer is designed.”IEC 62492-1• Use:– Tape measure– Measuring rod13
  14. 14. Non-mandatory EquipmentItems that may be used on special calibrations• Aperture• Frost / dew prevention14
  15. 15. Traceability Schemes• Scheme I– Contact traceability• Scheme II– Radiometric traceability15
  16. 16. Traceability Schemes4180 and 4181 scheme16SCHEME ISCHEME IISCHEME II
  17. 17. Laboratory Setup• Laboratory temperature limits– Ambient temperature uncertainty– Reflected temperature uncertainty17
  18. 18. Laboratory Setup - Incorrect• A heat source facing aflat-plate• A flat-plate facing anexterior wall– Especially a window• A flat-plate in thevicinity of air drafts– HVAC vent– Commonly used trafficway18
  19. 19. Laboratory Setup - Incorrect• A heat source facing aflat-plate• A flat-plate facing anexterior wall– Especially a window• A flat-plate in thevicinity of air drafts– HVAC vent– Commonly used trafficway19
  20. 20. Laboratory Setup - Incorrect• A heat source facing aflat-plate• A flat-plate facing anexterior wall– Especially a window• A flat-plate in thevicinity of air drafts– HVAC vent– Commonly used trafficway20
  21. 21. Laboratory Setup - Correct• Well controlled reflected temperature• Sufficient spacing from other instruments• Isolated from air drafts in room21
  22. 22. Controlling Reflected Temperature• Especially a concern for lower temperature calibrations22
  23. 23. Calibration Procedure• Preparation• Calibration Points• Procedure23
  24. 24. Preparation• Allow infrared thermometer time to reach roomtemperature (at least 15 minutes)• Lens cleaning– Only clean if requested by customer– Clean per manufactures instructions• Set up any special equipment• Set radiation source to desired temperature• Allow radiation source time to stabilize24
  25. 25. Calibration PointsWhat calibrations point to use?• Determined by the customer• Laboratory may offer advice– Over wide range, minimum 3 points– Narrow range, 1 or 2 points may be fine• Best practice to perform calibration from lowestcal point to highest25
  26. 26. Calibration ProcedureProcedure for each calibration point• Set IR thermometer reflected temperature (if available)• εIRT = εS– εS is adjustable on a 4180 and 4181• Align IR thermometer– Set distance (Z-direction)– Align side-to-side and up-and-down (X- and Y-directions)– IR thermometer should be no more than 5° from normal to targetsurface• Make measurement– Make measurement 10 times IR thermometer response time– For instance: IR thermometer respose time 0.5 s, make measurement for 5 s• Procedure < 15 s26
  27. 27. Procedure – Measuring Distance27
  28. 28. Procedure - Alignment• Laser Alignment• Maximizing Alignment28
  29. 29. Uncertainty Analysis29Uncertainty Desig. TypeU(100 °C)(°C)Source Calibration temperature U1 B 0.268Source emissivity U2 B 0.128Reflected ambient radiation U3 A 0.031Source heat exchange U4 B 0.012Ambient Conditions U5 B 0.001Source uniformity U6 A 0.163InfraredThermometerSize-of-source effect U7 B 0.019Ambient temperature U8 A 0.050Atmospheric absorption U9 B 0.020Noise U10 A 0.100Display Resolution U11 A 0.058Combined Expanded Uncertainty (k=2) 0.364
  30. 30. Reporting Your ResultsEvery report of calibration should contain:• Title• Unique identification of the calibrated infrared thermometer• Record of the person who performed the calibration• Date of calibration• Source temperature versus infrared thermometer readouttemperature• Measuring distance• Emissivity setting of the infrared thermometer• Diameter of the source• Ambient temperature• Description of the aperture including aperture distance (if used)• Measurement uncertainties30
  31. 31. Supplemental Information• Description of the calibration procedure• List of reference instruments• Traceability statement• Description of the uncertainty budget31
  32. 32. Summary• Follow proper procedure• Better calibration• Happy customers32
  33. 33. © 2013 Fluke CorporationThank you.For information about other web seminars in this series,including previously recorded web seminars, also offers in-depth training courses in calibrationand metrology. For class descriptions, schedules, andregistration, the first to know. Sign up for Fluke Calibratione-news bulletins, and the quarterly Total Solutions inCalibration