Vaisala HMP140 - Manual (Page 13)

HMP140A SERIES
U175en-1.5 Operating Manual
1999-12-08 9
4. CALIBRATION
4.1 One-point humidity calibration
The HMP140A series transmitters should be recalibrated approximately once a
year. The interval depends on the operating conditions and the required
accuracy. One-point calibration can be done with Vaisala’s portable HMI41
indicator equipped with an appropriate probe and optional calibration cable
(19116ZZ). The cable is connected to a test connector either on the main
component board of the HMP140A or, if a current output module is installed,
on the module (see Figure 4.1). For more detailed instructions, see the
operating manual of the calibration cable (U218en).
X15
X16
Current Module
DISPLAY CONNECTOR
VIO
SHIELD
GRN
YEL
BRN
PROBE CONNECTOR
Test connector for
one point calibration
on the main PCB
Test connector for
one point calibration
on the current
module
Figure 4.1 Location of the test connectors
4.2 Two-point humidity calibration
The calibration can also be done with the HMK11 or the HMK13B Calibrator,
or the instrument can be sent to Vaisala or a Vaisala representative.
4.2.1 Two-point humidity calibration procedure
•
Leave the calibrator and the transmitter for at least 30 minutes in the
same space so that their temperatures have time to equalize.
•
Place the probe into the calibration hole of the LiCl bottle in the
humidity calibrator.
•
Wait for 10 minutes.