Temperature Calibration (CT) - HMM100

HMM100 User Guide

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The following procedure describes a temperature (T) measurement calibration using serial line commands. You can use the procedure to do a one-point calibration (offset) or a two-point calibration (offset and gain). For two-point calibration, the second reference point must be at least 20 °C warmer than the first.

Temperature measurement is not controlled by the trimmers, so do not adjust them during temperature calibration.

  1. Connect the USB cable to the service port on the module, and to a USB port on your PC.
  2. Start a terminal application and set the correct connection settings. The default serial settings are 19200 8 N 1. Remember to check which COM port the USB cable is using.
  3. Verify that the connection works by giving the ? command:

    If the module does not respond with device information:

    • Check that the module is powered
    • Try the ?? command in case the module is in POLL state, open the line using the OPEN command if necessary
    • Check your serial line settings and cable connections
    • Power off the module, unplug the USB cable, restart the terminal application, and try again
  4. When your serial connection is working, use the L command to see the current user adjustment parameters and the status of the trimmers. Write down the T offset and gain values so you can restore them manually using the LI command, if necessary.
  5. Use the ERRS command to see that no errors are active:
  6. Use the PASS command to enable the advanced commands:
    >pass 1300
  7. Insert the probe in the temperature reference and wait for 20 – 40 minutes for the reading to stabilize.
  8. Give the CT command. The output from the command shows the currently measured T value, and prompts you to enter the value of the reference 1. This is the reference on the colder end, which produces the offset correction for the measurement.
  9. You now have three choices:
    1. To apply the correction, type the temperature of the reference in degrees Celsius and press ENTER.
    2. To exit the CT command without adjusting the measurement, press the ESC key and exit this procedure.
    3. To refresh the measured value without typing in the correction, press ENTER.
  10. If you only want to perform a one-point calibration (offset correction), press the ESC key after entering the correction. The CT command will exit, and you can move to 13.
    T 21.9847 Ref1 ? 22
    Press any key when ready

    To continue with the calibration of the warmer end (gain correction), press ENTER.

  11. Insert the probe in the second temperature reference and wait for 20 – 40 minutes for the reading to stabilize. The measurement reading for the second point will appear when the measured temperature is at least 20 °C warmer than the first reference point.
  12. Type the temperature of the second reference point and press ENTER to apply the correction.
    T 44.9847 Ref2 ? 45

    The CT command is now finished and both adjustments have been applied.

  13. Use the L command to verify that the new user adjustment parameters are in use:
  14. Use the SAVE command to save the changed settings:
    Saving settings...done
  15. Measure the value of the analog output to verify that the measurement is OK.