Chapter 5 ________________________________________________________________ Operation
VAISALA _______________________________________________________________________ 35
Relative humidity calibration must be done always after sensor
change.
Preparations before the calibration
Before the calibration the used sensor should be cleaned with
instrument air to blow out existing oil or gently first flush with
heptane (C7H14 16) and dry with instrument air to decrease response
time.
The claning shall be done as the dirty sensor can contamine the salt
bath and change the reference condition.
NOTE
It is important to clean the sensor before calibration as the dirty
sensor can contamine the salt bath and change the reference
condition.
Relative humidity calibration and adjustment
(in two points)
Relative humidity calibration and adjustment of the MMT318 and
MMT317 is done by using two reference humidities, difference
between the two humidity references must be at least 50% RH.
An easy calibration can be done by using Vaisala Humidity Calibrator
HMK15. If using HMK15 calibrator, please use the adapter fitting
(13.5 mm) with the MMT318 and MMT317 probe.
Before calibrations the MMT318 and MMT317 must be set to
adjustment mode by pressing once the adjustment button, see picture.
