Vaisala HMP228 User Manual
Page 28
HMP228
Operating Manual
M210282en-A
22
4.3.1
Two point calibration procedure
A two point calibration should be performed in stable conditions using
saturated salt solutions as references.
Disconnect the security lock jumper!
4.3.1.1
Using serial commands
•
Leave the calibrator and the transmitter for at least 4 hours in the
same space so that their temperatures have time to equalize. Remove
the filter cap on the transmitter.
•
Insert the sensor head into the calibration hole of the LiCl chamber of
the humidity calibrator.
•
Wait at least 30 minutes.
•
Give command CRH
>CRH
RH : 11.9 Ref1 ? yy.y
Press any key when ready...
•
If you want to see how the sensor stabilizes to the humidity in the
calibrator, enter c
RH : 11.9 Ref1 ? c
RH : 11.5 Ref1 ? c
RH : 11.5 Ref1 ? 11.3
Press any key when ready...
•
Insert the sensor head into the calibration hole of the NaCl chamber of
the humidity calibrator.
•
Wait at least 30 minutes.
•
Press any key and enter the second point value; press
RH : 75.5 Ref2 ? yy.y
•
The stabilization of the sensor can be monitored by entering c
instead of the reference value.
4.3.1.2
Using display/keypad commands
•
Leave the calibrator and the transmitter for at least 4 hours in the
same space so that their temperatures have time to equalize. Remove
the filter cap on the transmitter.
•
Select Cali in the main menu and then RH cal; select Not changed
and then two point calibration RH 2 point cal. Change the first point
reading with the arrow keys to correspond to the reference humidity
and press ENT; pressing an arrow once changes the reading by
0.05 %RH.