Chapter 6 ______________________________________________________________ Maintenance
VAISALA _______________________________________________________________________ 85
Cleaning RAINCAP
®
Clean Vaisala RAINCAP
Rain Sensor at least every six months, more
often if local conditions require it.
The measuring principle does not allow for proper ESD
protection of the
®
electronics, so you must follow the following instructions:
- Ground your hand first by touching grounded metallic parts of the
installation to remove excessive static charges from your body.
- Clean the RAINCAP
®
rain detector carefully with a soft, lint-free
cloth moistened with mild detergent. Be careful not to scratch the
surface.
- Check that the detector is free of ice and snow deposits.
Calibration
PWD22/52 is calibrated at the factory. Normally, PWD22/52 needs no
recalibration as long as the circuit boards are not changed and there are
no warnings or alarms.
The circuit boards do not need hardware calibration.
A periodic check every 6 months is recommended to check the visibility
calibration using the PWA12 calibration kit. If the check shows less than
±5 % change, recalibration is not recommended, because the change is
within the repeatability of the calibration procedure.
If any mechanical damage changes or weakens the optical measurement
path, that is, either the receiver or the transmitter, or the cross arm
supporting them, PWD22/52 must be replaced. If the receiver unit
(PWC22/52) or transmitter unit (PWT11) is replaced, both visibility and
contamination measurements need recalibration.
For information on how to calibrate the temperature sensor, see
Appendix D, Calibrating the TS Sensor, on page 115.
Visibility Calibration
The calibration is checked and adjusted with the PWA12 calibration kit.
The kit consists of a blocking plate and two opaque glass plates with
known scatter properties. The ZERO, CHEC, and CAL commands are
used in the procedure. The calibration procedure checks two points; zero
scatter signal and a very high scatter signal. The zero signal is obtained
using a blocking plate and the high signal using opaque glass plates.
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