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6.3 Weekly Maintenance
The minimum weekly requirements for maintaining a BSRN radiation station are as follows (in addition
to the daily maintenance):
(1) Check the desiccant in each sensor. Desiccant should norm ally last several m onths, but is
dependent upon atmospheric water vapour, the quality of radiometer seals, the size of the
desiccant chamber and the quality of the desiccant. In drier climates checking the desiccant
monthly may be sufficient while in areas where monsoon conditions occur, twice weekly
inspections should be made during the most humid season. Depending upon the type of sensor
and the type of ventilated housing, the shield portion of the ventilator may require removal
to check the desiccant. Once checked and replaced if necessary, the shield should be carefully
replaced ensuring that the top of the shield is below the level of the instrument receiver surface.
Whenever possible, desiccant should be changed during conditions of low relative humidity.
If the desiccant is not a bright blue/purple, it should be changed. Desiccant can be recharged
by drying. Therefore, no saving is gained by attempting to have the desiccant last another
week. The material removed from any instruments should be saved and re-activated by placing
in an oven at a low heat for several hours. The desiccant will return to its original colour when
dry. Desiccant should be stored in an air tight container.
(2) If not part of the normal data acquisition program, the resistance of each of the instruments
should be checked and recorded. Significant changes in resistance can be used to detect
system faults.
(3) If not part of the normal data acquisition program, a reference voltage source and reference
resistor should be used to test the stability of the response of the data acquisition system.
This should be repeated at various temperatures to determine the effect of temperature changes
on the data acquisition system when such systems experience temperature extremes (e.g.
data loggers kept in unheated outdoor enclosures).
6.4 Long-term maintenance
6.4.1 Semi-annual maintenance
(1) The pyranometers used for the measurement of global and diffuse radiation should be swapped.
For more information please see Section 8.3 on calibration.
(2) The pyrgeometer should be replaced for calibration. For details please see Section 8.4 on
calibration of pyrgeometers.
(3) Any wiring that has become cracked or brittle should be replaced. Any connectors that have
begun to corrode should be replaced.
(4) A careful inspection of all instruments should be made to determine aging. If radiation shields
etc. have begun to show signs of aging (brittleness, discolouration etc.) they should be replaced.
Pyranometers should be checked for excessive weathering, O-rings checked and lubricated
etc.
(5) All-weather housings for cavity radiometers should be cleaned and any internal electrical
connections checked and repaired as necessary. All weather-tight seals should be checked,
lubricated or replaced as appropriate. Fans motors should be check and lubricated or replaced
as necessary. Any other moving parts should be checked and lubricated according to the
manufacturer’s recommendations.
(6) Some trackers require semi-annual maintenance. Check with the manual provided with the
tracking device to determine these requirements.
(7) All seals in weather-tight enclosures should be checked and lubricated or changed if necessary.
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