DeltaOHM HD31, Operating Manual

Page: 96 / 154

HD31
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V1.6
hours at stable temperature so as the instrument and the saturated solutions may reach thermal
balance with the environment before starting the calibration procedure. To obtain a good calibra-
tion, it is essential that the probe and the solution have the same temperature. You should keep
in mind that the plastic material is a poor heat conductor.
The calibration must be performed in a temperature range from 15 to 30°C.
Full calibration procedure (FULL TUNING option):
1. Unscrew the protection cover of the probe and, if necessary, tighten the M12×1 thread ring
nut (the thread ring nut is necessary only for
∅ 14 mm probes).
Avoid any contact of the sensitive element with hands or any other object or liquids. If mois-
ture is inside the measurement chamber, dry it with clean absorbent paper .
2. Unscrew the closure cap of the 75%RH saturated solution. Tighten the thread ring nut with
the probe to the saturated solution container and wait for at least 30 minutes.
3. In the instrument, select the calibration option FULL TUNING and press F3 ( OK command)
to confirm.
4. The instrument suggests that the first calibration point is set to 75%RH ( SETPOINT line)
and displays the temperature and the relative humidity measured by the probe ( MEASURE
line).
Fig. 13.3.5: calibration at 75%RH
5. Using
S
and
T
, set the calibration point ( SETPOINT line) to the saturated solution value at
the measured temperature (see the table below).
TAB. 13.3.1: saturated solution at 75%RH
Temperature (°C) Solution 75%RH
15 75.6
20 75.4
25 75.2
30 75.0
6. When the reading is stable, press F3 ( OK command) to confirm. The instrument displays a
countdown ( ACQUIRING ) of a few seconds; at the end, a message is shown reminding that
the operation will change the calibration data of the probe, select YES ( F3 key) to continue
(or press F1 to select NO and exit), the instrument moves to the next calibration point.
Calibration point
Measured RH
Measured Temperature