Vaisala HMP240 - Manual (Page 47)

HMP240 series
M210300en User's Guide
45
6.1.1.3 With LED commands
• Make sure that the sensors of the transmitter and the
reference instrument are close to each other. Allow enough
time for the sensor heads to stabilize to the measurement
conditions
Disconnect the security lock jumper!
• Connect an ammeter/voltmeter to the analogue outputs
(connector X2); if the outputs are already connected e.g. to
a process computer and you do not want to disconnect
them, the current output can be measured at separate test
points located next to connector X15 (see Chapter 7.1).
Give command ¡¡¡l (see Chapter 5.2). At the first
calibration point the LED on the left flashes; adjust the hu-
midity point (offset) with the arrow switches to the refer-
ence value. One push of a switch changes the output by
0.05 %RH; the change of the output voltage or current de-
pends on the output scaling. Press ENT switch. The second
LED from left starts flashing; press ENT again.
NOTE
If neither channel normally outputs the RH reading,
during the calibration channel 1 outputs the RH reading
0...100%RH, corresponding to the current/voltage scale
selected for this channel.
6.1.2 Two point humidity calibration
A two-point humidity calibration should be performed in stable conditions
using saturated salt solutions as a reference. Read also the calibrator manual.
NOTE
If the sensor has been changed, the calibration has to be
done according to the instructions in Chapter 6.1.3.
6.1.2.1 With serial commands
• Leave the calibrator and the transmitter for at least 4 hours
in the same space so that their temperatures have time to
equalize. Remove the filter cap on the transmitter.
Disconnect the security lock jumper!