Campbell Scientific CSAT3B CSAT3B Three-Dimensional Sonic Anemometer - Page 67

Calibration

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CSAT3B Three-Dimensional Sonic Anemometer If monitoring shows the internal humidity of the CSAT3B rising above 50%, including during night time cooling cycles, the desiccant should be replaced with canisters that can be purchased from Campbell Scientific as pn 30749. The desiccant is held in the small canister that is installed on the underside of the anemometer block inside of the brass screw cap (see FIGURE 9-2). Use a large flat-headed screwdriver to unscrew the cap and remove the canister. Replace the old canister with an unused one. The new canister should appear blue in color. A pink-hued canister indicates that moisture has been absorbed, and the canister should be discarded and replaced with a new one. When replacing the brass screw cap, ensure the cap is tightened until the head of the screw is flush with the housing and the o-ring cannot be seen. FIGURE 9-2. Exploded view of CSAT3B desiccant canister 9.4 Calibration The CSAT3B is calibrated at the factory over the temperature range of −30 to 50 °C, as sonic transducer response is a function of temperature. Any measurements taken at temperatures outside of this range will be suspect. The CSAT3B does not require field calibration; however, it may require a factory recalibration every few years. An indication that the CSAT3B is due to be returned to the factory for recalibration is when diagnostic flags are persistent under dry conditions with little to no wind and with no obstruction in the ultrasonic paths. A wind offset greater than the specifications found in 57

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CSAT3B Three-Dimensional Sonic Anemometer
If monitoring shows the internal humidity of the CSAT3B rising above 50%,
including during night time cooling cycles, the desiccant should be replaced
with canisters that can be purchased from Campbell Scientific as pn 30749.
The desiccant is held in the small canister that is installed on the underside of
the anemometer block inside of the brass screw cap (see FIGURE 9-2). Use a
large flat-headed screwdriver to unscrew the cap and remove the canister.
Replace the old canister with an unused one.
The new canister should appear blue in color.
A pink-hued canister indicates
that moisture has been absorbed, and the canister should be discarded and
replaced with a new one.
When replacing the brass screw cap, ensure the cap
is tightened until the head of the screw is flush with the housing and the o-ring
cannot be seen.
FIGURE 9-2.
Exploded view of CSAT3B desiccant canister
9.4
Calibration
The CSAT3B is calibrated at the factory over the temperature range of
−
30 to
50 °C, as sonic transducer response is a function of temperature.
Any
measurements taken at temperatures outside of this range will be suspect.
The CSAT3B does not require field calibration; however, it may require a
factory recalibration every few years.
An indication that the CSAT3B is due to
be returned to the factory for recalibration is when diagnostic flags are
persistent under dry conditions with little to no wind and with no obstruction in
the ultrasonic paths.
A wind offset greater than the specifications found in
57