Vaisala DMP248 Service Manual download pdf (Page 61)

CHAPTER 6_______________________________________________________________ CALIBRATION

VAISALA _________________________________________________________________________ 55

CHAPTER 6 CALIBRATION

The DMP248 transmitter has been fully calibrated at the factory so

there should be no immediate need for recalibration. The transmitter

should be calibrated only if there is reason to believe that the

adjustments 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.

Humidity calibration should be performed at least once a year.

Humidity calibration

The DMP248 transmitter is calibrated against two accurate RH

references. The calibration can be performed by the end-user, or the

instrument can be sent to Vaisala or a Vaisala representative. A two-

point calibration can be performed with Vaisala’s HMK15 or

HMK13B Calibrator.

A Ø 13.5 adapter must be used when calibrating with the HMK13B

Calibrator. The adapter (part no. 16611) can be ordered from Vaisala

or Vaisala representatives.

Calibration can be performed by giving the commands using the press

switches inside the housing, through the serial bus (serial commands)

or through the menus on the local display (display/keypad

commands).

When LED commands are used and when the two analogue channels

do not output either 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 transmitter is calibrated at two points, the points must be

either 50 %RH or 50 C apart from each other.

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Vaisala DMP248 Service Manual Page 61