USER'S GUIDE____________________________________________________________________
58 __________________________________________________________________ M211024EN-B
Capacitance Calibration (CRH)
CAUTION
Adjusting the capacitance measurement affects measurement accuracy
across the entire temperature range. This command should be used only
when the sensor has been replaced, or the measurement has drifted
significantly. For normal adjustment, use the
RHCAL
command instead.
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
