Campbell Scientific PWC100 Present Weather Sensor Calibrator - Manual (Page 8)

PWC100 Present Weather Sensor Calibrator
Care must be taken not to drop or scratch either the velocity or visibility units
as this may cause errors that could result in tests failing when they shouldn’t.
2.2 Initial Configuration of the PWS100 for use of the Calibrator
The visibility calibration disks provided as part of the calibration kit are
individually calibrated and have a number printed on them to indicate the
measured signal in a reference instrument. Each PWS100 that is to be used
with the calibrator has to have that value entered into its configuration so that it
is referenced to the properties of that disk. Once set, the PWS100 will retain
the calibrator disk information unless the sensor is reset to its factory defaults.
The test procedure outlined in the rest of the manual can then be followed
repeatedly without changing the settings in the sensors.
For information on how to set calibration disk constants, please refer to Section
7.4.3 of the PWS100 manual. Figure 2-1 provides the screen in which the
values are shown. Please note you only need to change the constants; do not
attempt to adjust the calibration of the PWS100 if carrying out the standard test
procedure.
FIGURE 2-1. PWS100 calibration disk constants
For normal operation it is only necessary to set the visibility constant, as
printed on the disk. It is also useful to set the calibrator serial number for
reference purposes. The velocity and size constants can be left at the factory
defaults of 5.000 and 2.386 as these are fixed values for a standard calibrator.
3. PWS Calibration
The calibration check procedure can be broken up into two separate sections.
The first section comprises of visibility tests and the second velocity tests. If
only a visibility test is required, then the tests can be finished after the first
stage and the velocity tests need not be run.
It may be desirable to carry out a check of the sensor before and after cleaning
the sensor’s lenses to determine if the previous readings of the sensor were
adversely affected by dirt. This would be at the customer’s discretion.
2