Vaisala HMT360 - Manual (Page 70)

User’s Guide ______________________________________________________________________
68 ___________________________________________________________________ M010056EN-J
High End Adjustment (HMT360 without Display)
1. After having made the low end adjustment, insert the probe into a
measurement hole of the NaCl (75 %RH) salt chamber in the
humidity calibrator. Please, note that the difference between the two
humidity references must be at least 30 %RH.
2. The LED indicator lights up. Wait at least 10 ... 15 minutes for the
sensor to stabilize; use a multimeter to monitor the stabilization.
3. Press buttons Up and Dn to adjust the multimeter reading. Calculate
the current value corresponding to the reference humidity by using the
equations presented in
Calculating Correspondence of Current Values
and Output Quantities on page 64 .
4. Conclude the adjustment with button E.
5. Restore the DIP switch settings. Set the calibration DIP switch to
position disabled (down).
Low End Adjustment (HMT360 with Display)
1. Connect the power supply as instructed in section Connections on
page 63 . The measurement readings will be visible on the display
during calibration, but you can also connect a multimeter to check the
analog output readings.
2. Remove the filter and insert the probe into a measurement hole of the
dry end reference chamber (for example LiCl: 11 %RH) in the
humidity calibrator.
3. Power up the transmitter.
4. Set the internal DIP switch Calibration Enabled/Disabled to
position ON and select RH calibration by using switches 3 and 4 (see
section
DIP Switch Functions on page 45 ).
5. Press button C to ignore the automatic adjustment procedure. The
humidity reading measured by the transmitter appears on the display
and on the lower left corner you can see the text "Set Lo".
6. According to the calibrator used, wait at least 10 ... 15 minutes for the
sensor to stabilize; use the transmitter display to monitor the
stabilization.
7. Press buttons Up and Dn to adjust the display reading. Press button E
to conclude the low end adjustment.
8. To continue with the high end (two-point) adjustment follow the
instructions in the next section.
If the low end adjustment is sufficient, press button E again to
conclude the calibration. Also restore the DIP switch settings; set the
calibration DIP switch to position disabled (down).