Vaisala MM70 User Manual download pdf (Page 53)

Chapter 5 ___________________________________________ CALIBRATION AND ADJUSTMENT

Calibration and Adjustment of MM70 Series

Probes

General about Calibrations

The MM70 is fully calibrated as shipped from factory. Adjustment

should be done if there is a reason to believe that device is not within

the accuracy specifications. The recommended calibration interval is

one year.

It is recommended to send the device to Vaisala Service Centre for

calibration and adjustment, see contact information in section Vaisala

Service Centers on page 61. Alternatively, user can calibrate and

adjust MM70 by following the instructions below.

Preparations before the Calibration

Before calibration the used sensor should be cleaned with instrument

air to blow out existing oil or gently first flush with hepthane (C7H16)

and dry with instrument air. This is to decrease response time and to

prevent contamination of the salt bath and change of the reference

condition. See section MAINTENANCE on page 59.

NOTE

It is important to clean the sensor before calibration as the dirty

sensor can contamine the salt bath and change the reference

condition.

When using Vaisala humidity calibrator HMK15, use the adapter

fitting (13.5 mm hole). Before starting the adjustment mode, take out

the screw vovering the calibration button (item 3 in Figure 2). See

Figure 2 on page 11.

Relative Humidity Adjustment

Li-Cl-NaCl Automatic Adjustment

LiCl-NaCl automatic adjustment is a two-point adjustment in

reference humidities of 11.3 % (LiCl) and 75 % (NaCl). You don't

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Vaisala MM70 User Manual Page 53