PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
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Section 9. Maintenance<br />
It is advisable to use airduster to blow any loose dust and dirt from the lenses<br />
as a first step. Using a lint free lens cloth or lens tissue impregnated with a<br />
small amount of isopropyl alcohol solvent, clean the lens surface by dragging<br />
the cloth across the lens surface being careful not to apply excessive pressure.<br />
Excessive pressure may lead to some types of contaminant scratching the lens<br />
surface. Over time such scratches can lead to reduced sensor accuracy.<br />
Once clean, replace the baffle by carefully slotting it into position, being<br />
careful not to scratch the paint coating or damage any heater element. Lock the<br />
baffle into place using the retaining screw, ensuring that the nylon washer is in<br />
place.<br />
9.3 Calibration<br />
The <strong>PWS100</strong> is fully calibrated before leaving the factory. This calibration<br />
covers the mechanical arrangement of the system (including detection volume)<br />
as well as setting laser power and other electronic settings. The system is self<br />
regulating; however, it is recommended that the <strong>PWS100</strong> is calibrated every<br />
two years. If the calibration process is unable to bring it into specification, a<br />
warning LED will flash on the PWC100 calibrator. The <strong>PWS100</strong> should then<br />
be sent to the factory.<br />
The detection volume is calibrated using the PWC100 calibrator. The particle<br />
analysis is done using the unit with a rotating disc which has an embedded high<br />
precision ball lens. The refractive index of this ball lens is taken into<br />
consideration when calibrating the unit. The disc is rotated at a known speed<br />
which provides a known velocity component to the calibration and the<br />
refraction from the known diameter ball lens to the two detectors provides a<br />
size calibration. Visibility calibration is carried out using the second fixture<br />
which comprises a material with known scatter parameters. Light impenetrable<br />
sensor blocks are used to determine sensor offset and will need to be placed in<br />
the sensor heads when required. The unit will then determine the calibration<br />
factors and indicate if there is any problem with the optical or mechanical<br />
arrangement of the present weather sensor. Laser power can be monitored<br />
using a commercial laser power meter.<br />
Please refer to the PWC100 calibrator manual for further details of operation of<br />
the PWC100 calibrator and the procedure for calibration of the <strong>PWS100</strong>.<br />
9-2