Use the CRH command to perform a 1-point or 2-point correction to the capacitance measurement of the probe. This command changes the offset and/or gain of the humidity measurement, depending on the calibration and reference:
- 1-point calibration with a single < 50 %RH reference will adjust the offset of the capacitance measurement
- 1-point calibration with a single > 50 %RH reference will adjust the gain of the capacitance measurement
- 2-point calibration will adjust both offset and gain. The first point requires a < 50 %RH humidity reference, the second point must be > 50 %RH. There must also be at least 30 percentage point difference between the references.
CRH [reference]<cr>
This command is not available on the HMP110T.
When performing a 1-point calibration, you need to place the probe in the reference humidity and wait for 20 … 40 minutes for the humidity to stabilize. To apply the adjustment, enter the CRH command with the reference %RH as a parameter.
Example: 1-point calibration (LiCl reference, 11 %RH):
crh 11
OK
Example: 1-point calibration with NaCl reference (75 %RH):
crh 75
OK
Giving the command without parameters starts the 2-point calibration. Remember to allow the humidity to stabilize for 20 … 40 minutes after changing the reference.
Example: 2-point calibration with LiCl (11 %RH) and NaCL (75 %RH) references:
crh
RH : 11.2684 1. ref ? 11
Press any key when ready ...
RH : 75.0612 2. ref ? 75
OK