Vaisala HMP228 User Manual
Page 32
HMP228
Operating Manual
M210282en-A
26
•
Select Cali in the main menu and then RH cal; select Sensor
changed. Change the first point reading with the arrow keys and
press ENT.
•
Insert the sensor head into the calibration hole of the NaCl chamber of
the humidity calibrator.
•
Wait at least 30 minutes.
•
If necessary, change the second point reading with the arrow keys and
press ENT.
4.4.1.3
Using LED 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. '
•
Insert the sensor head into the calibration hole of the LiCl chamber of
the humidity calibrator.
•
Wait for 30 minutes.
•
Connect an ammeter/voltmeter to the analogue outputs (connector
X2). Give command l¡¡¡. At the first calibration point the LED
on the left flashes; adjust the first point (offset) with the arrow
switches to the value given in the calibration table (Chapter 4.4.5) and
press ENT switch.
•
Insert the sensor head into the calibration hole of the NaCl chamber in
the humidity calibrator.
•
Wait at least 30 minutes.
•
Check that the reading corresponds within the desired accuracy to the
value given in the calibration table (Chapter 4.4.5). If not, adjust the
second point with the arrow switches to the correct value and press
ENT. At the second calibration point the second LED from the left
flashes.
The basic capacitance of the new sensor may differ considerably from that of
the previous one. Therefore, the corresponding humidity reading of the
transmitter may be below 0 %RH at the low or above 100 %RH at the high
calibration point. However, the current/voltage reading of the analogue output
shows only the minimum or maximum value of the selected current/voltage
scale and the output value may not change even though the arrow switches are
pressed several times. If this happens, press the up or down arrow switch
continuously to bring the output back into the selected scale; this may take as
long as half a minute.