Vaisala HMP228 - 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 <cr>, enter the first point value and press <cr>.
>CRH <cr>
RH : 11.9 Ref1 ? yy.y <cr>
Press any key when ready...
• If you want to see how the sensor stabilizes to the humidity in the
calibrator, enter c <cr> instead of the first reference:
RH : 11.9 Ref1 ? c <cr>
RH : 11.5 Ref1 ? c <cr>
RH : 11.5 Ref1 ? 11.3 <cr>
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 <cr>.
RH : 75.5 Ref2 ? yy.y <cr>
•
The stabilization of the sensor can be monitored by entering c <cr>
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.