Vaisala HMP155 - Manual (Page 59)

Chapter 6 ___________________________________________________Calibration and Adjustment
VAISALA _______________________________________________________________________ 57
CHAPTER 6
CALIBRATION AND ADJUSTMENT
The Vaisala HUMICAP
®
Humidity and Temperature Probe HMP155 is
fully calibrated and adjusted as shipped from factory. Recommended
calibration interval is one year. Depending on the application, it is good
to make more frequent checks. Calibration must always be done when
there is reason to believe that the device is not within the accuracy
specifications.
It is recommended that calibration and adjustment is carried out by
Vaisala. See section Product Returns on page 55.
Calibration and adjustment can also be carried out either by using the
buttons on the probe or through the serial line connection.
NOTE Vaisala recommends that RH adjustment is carried out as a two-point
adjustment. With one-point adjustment, the required accuracy can only
be achieved if the actual measurement environment (RH and T) is the
same as the one-point adjustment environment.
Before attempting calibration, the ADJ button has to be held down until a
green LED lights up. This turns off the heating and the additional
temperature probe in the case you are using an HMP155 with either of
those options. After that HMP155 is ready to be checked and calibrated.
Because the T-probe is turned off during calibration, it does not need to
be inserted into the same reference conditions with the humidity probe.
If a chemical purge option is available, it should always be carried out
before calibration.
NOTE Button calibration is not available for the additional temperature probe.
In the passive output version of HMP155, the temperature cannot be
calibrated.