Vaisala DM70 - Manual (Page 29)

Chapter 5 _____________________________________________________________ User Interface
10. To deactivate analog output, go to Menu - Functions -
Analog output - Analog output on/off and press Off.
Auto-Calibration
To obtain the best possible accuracy in measurements taken in dry
environments, DM70 has a built-in, automatic calibration. During the
auto-calibration, DM70 adjusts the dry-end reading to correspond to
the calibrated values. This is a unique and patented method to avoid
errors in accuracy when monitoring low dewpoints.
The auto-calibration is carried out if the following criteria for the
measurement environment are fulfilled:
- Relative humidity must be <5 % (DMP74A).
<2 % (DMP74B/C).
- Temperature must be 0
- Humidity environment must be stable. The maximum change in the
dewpoint can be 1 ºC within 30 seconds.
NOTE Auto-calibration cannot operate if the above conditions are not
fulfilled.
If the adjustment in the auto-calibration reaches a preset, maximum
value or if the auto-calibration correction fails, for example, because
of unstable conditions, a new auto-calibration may take place later (if
the automatic auto-calibration is turned on). Auto-calibration can be
either automatic or manual.
Automatic Auto-Calibration
As a default, the automatic auto-calibration in DM70 is turned on. In
this mode, the calibration takes place automatically if the dewpoint or
temperature changes significantly, typically more than 10 ºC.
However, if there are no changes in the conditions, the calibration will
take place at an interval of one hour or at least, after one hour from the
last auto-calibration.
VAISALA _______________________________________________________________________ 27