7.4 One-Point Humidity Calibration and
Adjustment Using Handheld Meter and HMK15
Humidity Calibrator
• A fully charged Vaisala MI70 indicator (the measurement display that is
included in the HM70 package)
• Vaisala HMK15 Humidity Calibrator with the preferred salt solution prepared
(for example, LiCl (11 %RH) or NaCl (75 %RH))
• Connection cable for HM70 handheld meter (219980SP)
• Medium size cross-head screwdriver (Pozidriv)
1. Prepare the HMDW110 series transmitter for a service port connection.
a. Open the cover of the HMDW110 series transmitter.
b. If the terminal block for terminals 5 ... 8 is wired, pull it out. This disconnects the
transmitter from supply voltage and prevents possible equipment damage that may
be caused by ground loops. The locations of the terminal blocks and the service port
are shown in Component Board (page 13).
c. If the other terminal block is wired (terminals 1 ... 4), pull it out also. This prevents the
communication between the transmitter and the RDP100 remote display panel from
interfering with your connection.
2. Plug in the connection cable 219980SP to the service port of the HMDW110 series
transmitter, and the other end to port I of the MI70 indicator. If any other probes are
connected to the MI70, disconnect them.
3. Remove the filter on the probe. This exposes the sensors to damage, so handle the
transmitter carefully.
4. Unplug the Ø12 mm hole on the HMK15 salt jar and insert the probe.
5. Wait at least 15 minutes for humidity to stabilize.
Stabilization may take a much longer time if there are temperature dierences or the salt
solution is freshly made.
6. Turn on the MI70 indicator.
7. Select Functions > Adjustments from the menu of the MI70, then select Start.
8. The adjustment mode starts. Select OK.
9. Select RH as the parameter to be adjusted.
10. The adjustment mode should now show a stable, unchanging RH value. The dierence
between the measured value and the reference humidity of the jar should not be greater
than the combined measurement uncertainty of the HMDW110 series transmitter and the
salt jar.
Depending on the result, proceed as follows:
• If the HMDW110 series transmitter is within its accuracy specification, there is no need
to proceed with the adjustment. Select Back > Exit to leave the adjustment mode.
• If adjustment is required, continue with the next step.
HMDW110 User Guide M211726EN-D
58
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