Vaisala HMP155 User Manual download pdf (Page 61)

Chapter 6 ___________________________________________________Calibration and Adjustment

VAISALA _______________________________________________________________________ 59

Push-Button Calibration

Calibration and adjustment of the HMP155 can be done by using the

adjustment buttons found on the probe. The two-point humidity

adjustment is carried out by using two relative humidity references: for

example saturated salt points 11 % RH (LiCl) and 75 % RH (NaCl). The

difference between the two humidity reference points must be at least 30

%RH. The difference between the two temperature reference points must

be at least 30 °C.

NOTE

In push-button calibration, the probe outputs are by default relative

humidity in the range 0…100 %RH in CH1 and temperature in the range

-40…+60°C in CH2.

Two-Point Humidity and Temperature

Adjustment

To make a humidity or temperature adjustment:

1. Carry out the chemical purge (if available). See section Chemical

Purge (Optional) on page 45.

2. Uncover the adjustme

nt buttons on the probe by removing the

protective cover and removing the calibration seal.

3. Open the protective plug and you can see three buttons marked

-, □

and

+. There is also a two-colored indicator LED. See Figure 13 on

page 58.

4. Press the

ADJ button and hold it down until the green indicator

LED lights up. This puts HMP155 in RH calibration mode.

5. Remove the filter and insert the probe into a measurement hole of

the dry end reference chamber (for example, LiCl: 11 % RH) to do

the low humidity offset adjustment.

NOTE

Do not touch the adjustment buttons before the conditions have

stabilized. This takes approximately 30 minutes.

6. Using the

- and + buttons, make sure the A

out

voltage is correct and

press the

ADJ button. Green indicator LED turns off and back on.

NOTE

Do not touch the adjustment buttons before the conditions have

stabilized.

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