Vaisala HMP230 - Manual (Page 59)

HMP230 SERIES
M210225en-B User's Guide
53
7. CALIBRATION
The HMP230 transmitters have been fully calibrated at the factory and there
should be no immediate need to calibrate them again. The transmitters should
be calibrated only if there is reason to believe that the adjustments of the
transmitter have changed. The adjustments of the temperature measurement
channel and the analogue outputs are particularly stable and in normal
circumstances there is no need to recalibrate them. It is recommended that
humidity calibration is performed at least once a year. See the chapter 10
Factory calibration and repair service.
7.1. Humidity calibration
The calibration of the HMP230 transmitters can be checked with a calibrated
Vaisala humidity meter, such as the HM34. The HMI41 indicator or the
HMI38 data processor with an appropriate reference connection cable can be
used as a field calibrator. A two-point calibration can be made with the
HMK15 or with the HMK13B Calibrator or the instrument can be sent to
Vaisala. We recommend recalibration at least once a year. The instruments
must be recalibrated every time the HUMICAP

humidity sensor is changed.
When calibrating with the HMK13B calibrator, an adapter is necessary (part
no. 16611). Calibration can be performed by giving the commands using the
press switches inside the housing, through the serial bus or through the menus
on the local display.
When LED commands are used and when the two analogue channels do not
output relative humidity and/or temperature, relative humidity is calibrated on
channel 1 and temperature is calibrated on channel 2. The calibration ranges
are 0...100 %RH and -20...+80 °C. When the transmitters are calibrated at two
points, the points must be either 50 %RH or 50 °C apart from each other.
NOTE
If the transmitter includes the re-gaining option, the
sensor re-gaining must always be made before humidity
calibration. Before starting the calibration, make sure
that the temperature of the composite sensor has come
down to ambient temperature (see Appendix 9).