Kipp&Zonen BSRN Scientific Solar Monitoring System - Manual (Page 60)

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the radiom eter dome by sand or by hyrdom eteorites such as hail. If the dom e is dam aged,
it should be replaced with one m ade of the sam e optical m aterial. The change should
be docum ented and the dom e kept for future reference. Although dom es do not norm ally
change the overall calibration of the system , the instrum ent with the new dom e should
be m onitored for any differences, particularly changes in directional responsivity.
(i) Pyrgeometers: Daily cleaning of the dom e of the pyrgeom eter should take place when
the other instrum ents are cleaned. Particulate residues should be rem oved using a
soft brush or gentle airstream . The dom e can be wiped with a lint-free cloth. In cases
where m aterial has adhered to the dom e, a cloth m oistened with deionized water can
be used.
(2) The radiom eter should be checked for any condensation on the inside surface of the outer
dom e. If this occurs, the outer dom e m ust be rem oved in a clean, dry location, cleaned and
the cause for the leak determ ined. The most probable cause is poor m aintenance of the desiccant
(see weekly m aintenance). If the desiccant has been changed within a week, the probable
cause is a poor ‘O’ ring seal. A replacem ent is required. If m oisture is found on the inner surface
of the inner dom e, the instrum ent should be replaced with a spare instrum ent and the faulty
instrum ent sent for service.
(3) The colour and the condition of the therm opile should be checked. If the colour is fading or
changing; or the therm opile surface appears rough, cracked or weathered; the instrum ent
should be rem oved from service and replaced with a spare. On newer instrum ents this occurs
rarely.
(4) The level of each horizontally m ounted instrum ent (e.g., pyranom eters, pyrgeom eters) should
be checked and corrected as necessary. The bubble of the circular level should be com pletely
within the inner circle. For m ost instrum ents, this indicates that the instrum ent is level to within
±0.1°.
(5) The cabling leading from the instrum ent to the data acquisition system or junction box should
be inspected for wear. Unless the cable is to be replaced, or m ust be untangled, the instrum ent
should not be disconnected. All work on the cable should be appropriately docum ented. In
cases where a cable is functional, but aging, a tim e should be set for its replacem ent during
the station sem iannual or annual m aintenance (see below).
(6) The ventilator m otors should be checked on a daily basis. If the m otor is not operating properly,
the problem should be corrected or the m otor replaced. All procedures should be docum ented,
including the start and end tim e of the work. If knowledge of when the ventilator began to
m alfunction is known (e.g., lightning strike) this should also be included in the log. On those
ventilators where the cover acts as a radiation shield, the top of the cover m ust be situated
below the receiver surface of the radiom eter.
(7) The pointing of any instrum ents should be checked and, if necessary, corrected. The reasons
for possible m isalignm ent are partially dependent on the type of tracker being used. The sun
m ust be shining to detect spot alignm ent for direct beam instrum ents; however, the checking
of clock tim es and general system failures is independent of weather conditions.
(i) One-axis solar tracker
- the solar declination m ust be checked and adjusted to align the solar spot with the
instrum ent target.
- as m ost one-axis trackers use synchronous m otors, the power frequency m ust be
m onitored to ensure that the tracker is being driven at the correct speed.
- the tracker m ust be inspected to ensure that no m echanical m alfunction has occurred
(e.g., slippage in the clutch)
- In one-axis trackers, unless especially equipped, the cables attached to the instrum ents
m ust be m anually unwound each day.