Vaisala WMS302 Betriebsanweisung PDF herunterladen (Seite 175)

Chapter 6 ______________________________________________________________ Maintenance

VAISALA______________________________________________________________________ 173

Changing the HUMICAP®180 Humidity Sensor

Unscrew the filter. Remove the damaged sensor and mount a new

HUMICAP®180 humidity sensor in its place. Handle the sensor with

care. Calibrate the probe using a two-point calibration procedure.

Humidity Calibration

For a high-accuracy two-point calibration, use a Vaisala HMK15

calibrator and saturated salt solutions. Refer to the appropriate manual

for details.

Easiest way of doing the calibration is to use HMI41 Indicator with the

HMH40-MAWS Handle for the probe head. Note that this setup is only

for relative humidity and no temperature readings are displayed.

0406-072

Figure 145 HMH40-MAWS Handle

Leave the calibrator and the probe head in the same space for at least

four hours so that their temperatures have time to equalize. Unscrew the

plastic grid of the probe.

The calibration is done first for the dry end (<50 %RH) and then for the

wet end (>50 %RH) by adjusting the trimmer potentiometers marked

with D (dry) and W (wet). The potentiometers are located under a

protective plug. Use a ceramic with 2.5 mm (0.1 in.) blade for adjusting

the potentiometers.

NOTE

If zero point is calibrated in nitrogen (N2), the minimum output signal

of 0.008 V corresponds to a relative humidity of 0.8 %RH.

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Vaisala WMS302 Betriebsanweisung Seite 175