Vaisala MMT330 - Manual (Page 155)

Chapter 8 ___________________________________________________ Calibration and Adjustment
VAISALA _______________________________________________________________________ 153
Using Serial Line
Note that the difference between the two humidity references must be at
least 50 %RH.
1. Connect the MMT330 to a PC. See section Serial Line
Communication on page 78. Open a terminal program.
2. Press the ADJ button.
3. 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 in the humidity calibrator HMK15). Use the adapter
fitting for the MMT332, MMT337 and MMT338 probes.
4. Enter the CRH command and press ENTER.
CRH
5. Wait at least 30 minutes for the sensor to stabilize.
6. Type C and press ENTER a few times to check if the reading is
stabilized.
7. When the reading is stabilized, give the reference humidity after
the question mark and press ENTER.
>crh
RH : 11.25 Ref1 ? c
RH : 11.25 Ref1 ? c
RH : 11.25 Ref1 ? c
RH : 11.24 Ref1 ? c
RH : 11.24 Ref1 ? 11.3
Press any key when ready ...
8. Now the device is waiting for the high end reference. Insert the
probe into a measurement hole of the high end reference chamber
(for example,. NaCl: 75 %RH chamber in the humidity calibrator
HMK15). Use the adapter fitting for the MMT332, MMT337 and
MMT338 probes. Press any key when ready.
9. Let the probe stabilize for about 30 minutes. You can follow the
stabilization by typing C and pressing ENTER.
10. When stabilized, type the high end reference value after the
question mark and press ENTER.
>crh
RH : 11.25 Ref1 ? c
RH : 11.24 Ref1 ? c
RH : 11.24 Ref1 ? 11.3
Press any key when ready ...
RH : 75.45 Ref2 ? c
RH : 75.57 Ref2 ? c