Temperature Transmitter Calibration

[From:来自网络] [Author:admin] [Date:11-10-09] [Hit:]

Typical Procedure:

  1. Set up the temperature transmitter as shown in the picture below.
  2. Switch on the thermo bath / temperature generator power supply.
  3. Check the temperature transmitter span in the related datasheet.
  4. Carry out the five point calibration start from 0% to 100% of span range value.
  5. First, set the temperature at temperature bath to 0% of the transmitter span range value.
  6. Read the ampere meter reading (wait until the reading is stable) and record it.
  7. Repeat step 5 to 6 for 25%, 50%, 75%, and 100% of the transmitter span range value.
  8. Repeat step 5 to 6 for downscale start from 100%, 75%, 50%, 25%, and 0%.
  9. Calculate the % error for each test point and check whether it still under an acceptable range.
  10. If all result still in the acceptable % error range, then the calibration is finish. If there is some test point that shows the result out of acceptable % error range, then do the next step.
  11. Set temperature bath at 0% of the transmitter span range value. The ampere meter reading shall be 4 mA. If the reading is already 4 mA then continue to next step. If the reading not 4 mA then adjust the zero potentiometer of transmitter until the ampere meter read 4 mA. The zero adjustment also available though HART communicator by using zeroing application.
  12. Set temperature bath at 100% of the transmitter span range value. The ampere meter reading shall be 20 mA. If the reading is already 20 mA then back to step 5. If the reading not 20 mA then adjust the span potentiometer of transmitter until the ampere meter read 4 mA. The span adjustment also available though HART communicator by using span application.

Below is example of temperature transmitter calibration with span 100 oC with minimum temperature range is 35 oC. This calibration is concluded as satisfactory since all test point are have the % Error of Span under the rated % Error of Span stated in the datasheet (lets say 0.25% of span).

Test Point Ampere Meter Reading (mA) Thermo Bath Temperature Span of Transmitter Error Calculation % Error of Span
0% 4.01 35 oC 100 oC (((((4.01-4)*100/16))+35)-35)/100*100 0.0625
25% 7.97 60 100 oC (((((7.97-4)*100/16))+35)-60)/100*100 -0.1875
50% 11.99 85 100 oC (((((11.99-4)*100/16))+35)-85)/100*100 -0.0625
75% 16.02 110 100 oC (((((16.02-4)*100/16))+35)-110)/100*100 0.125
100% 20.03 135 100 oC (((((20.03-4)*100/16))+35)-135)/100*100 0.1875
75% 15.99 110 100 oC (((((15.99-4)*100/16))+35)-110)/100*100 -0.0625
50% 12.01 85 100 oC (((((12.01-4)*100/16))+35)-85)/100*100 0.0625
25% 8.03 60 100 oC (((((8.03-4)*100/16))+35)-60)/100*100 0.1875
0% 3.97 35 oC 100 oC (((((3.97-4)*100/16))+35)-35)/100*100 -0.1875

Notes:

To calculate the % Error of Span we can apply the following equation derived from simple linear interpolation.

% Error of Span = (((((I-4)*Span/16)) +Io)-TB)/Span *100

Where I = Ampere Meter Reading

Io = 0% Span Temperature

TB = Thermo Bath Temperature

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