Vaisala HMM100 - Manual (Page 60)

User's Guide _______________________________________________________________________
58 ___________________________________________________________________ M211024EN-C
Humidity Calibration (CRH)
Adjusting the capacitance measurement affects humidity measurement
accuracy across the entire temperature range. Take care when making
this adjustment.
CAUTION Be sure to write down the current capacitance adjustment parameters
(visible with the L command) so that you can restore them manually if
necessary.
The procedure below provides a calibration procedure using the serial
line commands and the Vaisala Humidity Calibrator HMK15. You can
use the procedure to do a one-point calibration (offset) or a two-point
calibration (offset and gain).
- One-point calibration requires a < 50 %RH reference
- Two-point calibration requires additionally a > 50 %RH reference,
with over 30 %RH difference between the two points.
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 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 Cp offset and gain values so you can
restore them manually using the LI command, if necessary.
>l
5. Use the ERRS command to see that no errors are active:
>errs