Vaisala HMP155 - Manual (Page 65)

Chapter 6 ___________________________________________________Calibration and Adjustment
VAISALA _______________________________________________________________________ 63
Serial Line Calibration
Two-Point Humidity Adjustment
Note that the difference between the two humidity references must be at
least 30 %RH.
To make a humidity adjustment:
1. Connect the HMP155 to a PC. See section Serial Line
Communication on page 24. Open a terminal program.
2. Carry out the chemical purge (if available). See section Chemical
Purge (Optional) on page 45.
3. Press the ADJ button and the green LED lights up.
4. Remove the filter from the probe and insert the probe into a
measurement hole of the dry end reference chamber (for example,
LiCl: 11 % RH).
5. Enter the CRH command and press ENTER.
6. Wait at least 30 minutes for the sensor to stabilize.
7. Press ENTER a few times to check if the reading has stabilized.
8. When the reading has stabilized, give the reference humidity after
the question mark and press ENTER.
>crh
RH : 16.6675 1. ref ?
RH : 16.4978 1. ref ?
RH : 16.3956 1. ref ? 11.25
Press any key when ready ...
RH : 11.25 Ref2 ?
9. Now the device is waiting for the high end reference. Insert the
probe into the measurement hole of the high end reference chamber
(for example, NaCl: 75 % RH chamber in the humidity calibrator
HMK15). Press any key when ready.
10. Let the probe stabilize for about 30 minutes. You can follow the
stabilization by pressing ENTER.
11. When stabilized, type the high end reference value after the
question mark and press ENTER.
RH : 75.45 Ref2 ?
RH : 75.57 Ref2 ?
RH : 75.55 Ref2 ?
RH : 75.59 Ref2 ? 75.5
OK
12. OK indicates that the adjustment has succeeded and the new
calibration coefficients are calculated and stored.