Chapter 4 ________________________________________________________________ Operation
VAISALA _______________________________________________________________________ 37
Calibrate Capacitance Measurement
Use the
CRH
command to perform a one-point or two-point correction to
the capacitance measurement of the module. This command changes the
offset and gain of the measured capacitance, and therefore affects
humidity measurement over the entire temperature range.
CAUTION
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.
CRH
<cr>
When performing a one-point calibration, you need to place the probe in
a single humidity reference with RH < 50%. Run the command and enter
the exact RH of the reference after the measurement has stabilized. Exit
the command by pressing the ESC key before proceeding to the second
point (see example 1 below).
For two-point calibration, the first point requires a RH < 50% humidity
reference, the second point must be RH > 50%. There must also be at
least 30 percentage points of difference between the references.
Example: one-point calibration
>crh
RH: 11.29915720 Ref1 ? 11.3
Press any key when ready
>
Example: two-point calibration
>crh
RH: 11.29915720 Ref1 ? 11.3
Press any key when ready
RH: 75.04306440 Ref2 ? 75
OK
>
