1-point adjustment of RH measurement (HMP110 and HMP113) - HMP110 - HMP113 - HMP60 - HMP63

HMP60 and HMP110 Series User Guide

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User guide
You can also use Vaisala Insight software for performing calibration and adjustment. See Vaisala Insight software.

To perform a 1-point adjustment to the capacitance measurement of the HMP110 or HMP113 using serial line, you need:

  • Vaisala USB cable (item code 219690)
  • PC with a terminal application
  • One humidity reference. 1-point adjustment with a single < 50 %RH reference adjusts the offset parameter of the measurement. 1-point adjustment with a single > 50 %RH reference adjusts the gain parameter of the measurement.

The following example procedure uses the HMK15 Humidity Calibrator. LiCl salt (11.3 %RH at 25 °C) is used as the reference point.

For more information on using a humidity calibrator and salt chamber references, see Vaisala Humidity Calibrator HMK15 User Guide M210185EN.
  1. Connect the USB cable to the PC, but do not connect it to the probe yet.
  2. Remove the filter from the probe and insert the probe in the LiCl salt chamber of the humidity calibrator (11.3 %RH).
  3. 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.
  4. Wait for 20 … 40 minutes for the humidity to stabilize.
  5. Start the terminal session and connect the USB cable to the probe. If your probe is in the analog output mode, press ENTER a few times to start it in RS-485 mode.
  6. Verify that the connection works by giving the ? command.

    If the probe does not respond with device information:

    • Disconnect the USB cable from the probe and retry. If your probe is in the analog output mode, press ENTER a few times immediately after connecting the USB cable.
    • Try the ?? command in case the probe is in POLL mode, open the line using OPEN command if necessary.
    • Check your serial line settings and cable connections.
  7. When your serial connection is working, use the L command to see the current user adjustment parameters.
  8. Use the ERRS command to see that no errors are active.
  9. Give the CRH command, with the %RH value of the reference as a parameter (in this case 11.3 for LiCl).
    crh 11.3
  10. Check with the L command that the user adjustment parameters have changed.