Campbell Scientific IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer - Manual (Page 37)

IRGASON ® Integrated CO
2
/H
2
O Open-Path Gas Analyzer and 3D Sonic Anemometer
9.2.2 Gas Analyzer Wicks
IRGASON gas analyzer windows are polished and slanted at an angle to
prevent water from collecting on their surfaces. However, due to increased
surface tension at the interface with the snout, water can pool at the edges and
partially block the optical path and attenuate the signal. To minimize the
occurrence of such events and the resulting data loss, consider using wicks.
The weave of the wick fabric promotes capillary action that wicks the water
away from the edge of the windows. The seam and the straight edge of the
wicks are permeated with a rubberized compound to prevent them from
shifting during operation.
Proper installation of the wicks is critical. They should not block or encroach
on the optical path. Before installation, record signal strengths for both H
2
O
and CO
2
. Following installation, these values should be unchanged.
Wicks are available as listed in TABLE 9-1.
TABLE 9-1. Rain Wick Replacement Parts
Wick
Campbell Scientific, Inc.
Part Number Campbell Scientific Description
Bottom
Wick
28652 FAB EC150/IRGASON RAIN
WICK BOTTOM
Top Wick 28653 FAB EC150/IRGASON RAIN
WICK TOP
The top wick has a short seam which has to be aligned with the short side of
the top snout. The angled edge of the wick must closely follow the edge of the
window without encroaching on the optical path (see FIGURE 9-3, Proper
location of the sonic top wick and bottom wick). The bottom wick is installed
in a similar manner, except the long seam should be aligned with the long side
of the bottom snout. Once in place, the wicks should fit snuggly over the
cylindrical part of the snout without any creases or wrinkles.
The wicks are constructed with a UV-resistant fabric and should function over
long time periods. Nevertheless, they should be inspected periodically. Check
for contamination from dust, pollen, pitch or other debris. If needed, wash
them in warm water with mild detergent or replace them. When performing
the zero-and-span procedure, the wicks should be removed before installing the
zero-and-span shroud.
Remove the wicks during the winter. The wicks will accumulate snow or
freezing rain, resulting in blockage of the optical path. Besides the wicks,
controlling the heaters in the snouts is another method the user may consider in
preventing data loss during precipitation and condensation events. The heaters
can be controlled statically using the Setup window in ECMon or dynamically
using a datalogger (see Section 10.2, EC100Configure() Instruction, for more
details).
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