Campbell Scientific Q7_1-L REBS Net Radiometer - Manual (Page 9)

Q-7.1 NET RADIOMETER
7
4.4 WINDSHIELD REPLACEMENT
Polyethylene deteriorates with exposure to
solar radiation. Inspect the windshields
frequently and replace as required (probably
every 3-6 months).
Always check for:
1. Condensation inside the windshields,
possibly indicating a leak.
2. Cracking or crazing of the windshields
(which usually appears first along the base).
Prompt replacement is essential if any of these
conditions occur. Also, if the windshields are
removed for any reason after more than one
month’s use, replace them with new ones. The
windshields should always be replaced as a set.
Windshield replacement may cause a slight
change in calibration, although this is unlikely
to exceed 3%.
CAUTION: There are very fine wires
inside the head of the Q-7.1 which are very
susceptible to corrosion if subjected to
moisture, e.g. standing water. It is
essential to carry out the preemptive
maintenance mentioned above to prevent
serious damage to the sensor.
Replace the windshields as follows:
1. Remove the mounting screws and clamping
rings.
2. Replacement windshields are pre-cut and
punched with holes. Make sure the O-rings
are in their grooves before clamping the new
windshields into place as described in step
3.
3. Gently tighten the screws in the following
sequence: first, third, fifth, second, fourth,
sixth. It does not matter which screw you
treat as the first. Continue the sequence
until the windshields are evenly in contact
with the clamping rings and frame.
4. Tighten the screws in the same sequence
until no space remains between either
windshield flange and its corresponding
mounting ring or frame surface. Make sure
both upper and lower windshields are
completely seated on the frame around the
entire periphery.
CAUTION: Do not attempt to dismantle
the instrument body. If internal attention is
needed, contact Campbell Scientific, Inc.
for repair.
If the windshields become dented, remove the
dents as follows:
1. Remove the vinal cap from the support arm.
2. Blow gently into the end plug breather hole
to inflate the windshields.
Remember to replace the support arm vinal
cap. Orient the vinal cap so the holes point
towards the ground.
CAUTION: When replacing the
windshields, take great care not to touch or
mark the black surfaces of the thermopile
as this may affect the performance of the
instrument. Take care also to avoid
overtightening the mounting screws.
4.4.1 Bird Damage
One other cause of damage to windshields is
birds pecking at the domes. A simple measure
to prevent this is to attach two or three 8 inches
cable ties to the support arm at the end near
the sensor head, with the free ends of the ties
pointing upwards to form an array of ‘spikes’.
This may discourage birds from landing on the
arm. If this does not work you may have to
resort to more drastic techniques such as
installing an artificial snake on the support arm
or commercial bird scarers.
4.5 CALIBRATION
Q-7.1 net radiometers show excellent stability
over long periods, but for serious use, regular
calibration checks are recommended. The
calibration can be checked in the field by
mounting another net radiometer alongside and
comparing results. The instruments should be
examined carefully if the results differ by more
than a few percent. Under normal
circumstances, a calibration check every six
months is adequate providing the sensitive
thermopile surface has not been marked,
damaged or exposed to the weather.
If the calibration can not be checked in the
field, Radiation Energy Balance Systems