Vaisala HMW90 - Manual (Page 70)

User's Guide _______________________________________________________________________
68 ___________________________________________________________________ M211399EN-F
Calibration and Adjustment
HMW90 series transmitters are fully calibrated as shipped from factory.
Calibration and adjustment services are available through Vaisala Service
Centers. For contact information, see www.vaisala.com/servicecenters .
HMW90 series transmitters have a display that makes it easy to compare
the measured readings against any portable calibration reference. Note
that depending on the ordered configuration, the display may be hidden
under the sliding cover.
For adjustment of the measurement, you have the following options:
- 1-point adjustment using the trimmers under the sliding cover. See
section Adjustment Using Display and Trimmers on page 69.
- 1-point or 2-point adjustment using the service port. See the following
sections:
- Adjustment Using an HM70 on page 70.
- Adjustment Using a PC on page 71.
- Replacement of the Humidity and Temperature Module HTM10,
which can be ordered as a spare part. See section Replacing the
Measurement Module on page 72.
The adjustment of temperature measurement is always a simple 1-point
offset correction.
The 1-point humidity adjustment of the HMW90 series adjusts both
offset and gain, depending on the adjustment condition. In a dry
condition (for example, 11 %RH), offset is adjusted more than gain.
NOTE The 1-point humidity adjustment requires that the target condition is at
least 50% of the currently measured value. This prevents the user from
making excessive corrections that are very unlikely to be needed.
However, if you feel that you may have done an incorrect adjustment,
you can easily remove the adjustment using the HM70 or the
CRH RESET command on the serial line.
NOTE Only T adjustment is available on the TMW92 and TMW93 transmitters.