Vaisala HM70 - Manual (Page 63)

Chapter 12 ______________________________ Calibration and Adjustment of HM70 Series Probes
VAISALA _______________________________________________________________________ 61
CHAPTER 12
CALIBRATION AND ADJUSTMENT OF
HM70 SERIES PROBES
General Information about Calibrations
The HM 70 is fully calibrated as shipped from factory. Adjustment
shall be done if there is a reason to believe that device is not within
the accuracy specifications. However, if
HM 70 is used as a reference
instrument in humidity measurements, the humidity recalibration is
recommended every year.
It is recommended to send the device to Vaisala Service Centers for
calibration, see contact information on page 68. Alternatively user can
calibrate and adjust HM70 by following the instructions given in this
chapter.
When using Vaisala humidity calibrator HMK15, use the adapter
fitting (13.5 mm hole) with the probes HMP76 and HMP77. Probe
HMP75 does not need the adapter fitting. If chemical purge option is
available, it should always be performed before calibration, see page
34.
Before starting the adjustment mode, remove the screw that covers the
calibration button. Refer to Figure 2 on page 11 for the location of the
button.
Relative Humidity Adjustment
LiCl-NaCl Automatic Adjustment
LiCl-NaCl automatic adjustment is a two-point adjustment in
reference humidities of 11.3 % (LiCl) and 75 % (NaCl). You do not
have to feed the reference values, the HM70 displays the accurate
value based on the measured temperature and the Greenspan table