Calibration and adjustment, Calibration, User calibration and adjustment – Vaisala DMT340 User Manual
Page 155: Chapter 7, Chapter 7, calibration and adjustment, pr
Chapter 7 ___________________________________________________ Calibration and Adjustment
VAISALA _______________________________________________________________________ 153
CHAPTER 7
CALIBRATION AND ADJUSTMENT
Calibration
DMT340 is fully calibrated and adjusted as shipped from the factory. The
typical calibration interval is two years. Calibration must always be done
when there is reason to believe that the device is not within the accuracy
specifications.
It is recommended that the device is sent to a Vaisala Service Center for
calibration and adjustment. For contact information of Vaisala Service
Centers, s
Vaisala hand-held dewpoint meter DM70 can also be used to calibrate
the transmitter.
User Calibration and Adjustment
When adjusting DMT340, the reading is changed to correspond to the
reference value. After the adjustment, the original calibration certificate
shipped with the product is no longer valid.
NOTE
Dewpoint calibration should be carried out in Vaisala or in other
laboratory conditions.
The reference condition of the dewpoint must be traceable to the
appropriate standards. The user adjustment requires a stable humidity
generator capable of producing the required humidities and a calibrated
reference dewpoint meter. For adjustment, the probe and the reference
dewpoint meter are connected to the humidity generator output, the
reference condition is adjusted and let to stabilize. After the probe and
the reference dewpoint meter are stabilized, the DMT340 reading is
adjusted to correspond the reference value.
For the adjustment of DMT340 equipped with DRYCAP
®
180M-sensor,
the reference low dewpoint temperature should be between -57 °C and -
67 °C (-70.6 °F ... -88.6 °F) in the gas temperature of approx. +20 °C.