Campbell Scientific CSAT3 CSAT3 3-D Sonic Anemometer - Page 47

Calibration

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CSAT3 Three Dimensional Sonic Anemometer FIGURE 11-2. P/N 28902 CSAT3 Sonic Wick Spares Kit contents 11.2 Calibration The CSAT3 is calibrated over the temperature range of -30° to +50°C (standard) or -40° to +40°C (cold shifted). The CSAT3 may or may not make measurements outside the calibration range. Any measurements taken outside the calibration range will be suspect. The CSAT3 does not require any field calibration. WARNING The CSAT3 electronics box contains unique calibration information for its respective sensor head. Do not mismatch CSAT3 sensor heads and electronics. Doing so will result in erroneous wind and speed of sound measurements. If the CSAT3 requires a calibration, it will develop a wind offset greater than the specifications, or it will set diagnostic flags, under dry conditions with little to no wind and with no obstruction in the ultra sonic paths. CSAT3s running embedded code version 4 will develop the offset first and then possibly set diagnostic flags under dry conditions. CSAT3s running embedded code version 3 will set diagnostic flags before a wind offset develops. 11.2.1 Cold Shifted Calibration A CSAT3 with a cold shifted calibration is calibrated over the temperature of -40° to +40°C. To improve the speed of sound reporting resolution, the CSAT3 sends the speed of sound minus an offset to a datalogger via the SDM interface or a PC via the RS-232 interface. The data acquisition system must add the appropriate offset to determine the speed of sound. For the standard temperature range the offset 340 m s-1. This offset is added by the CSAT3()/SDM-CSAT3 (P107) instruction Command/Option 90, 91, 98, and 99. For the cold shifted calibration range, the offset is 337 m s-1. 39

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CSAT3 Three Dimensional Sonic Anemometer
FIGURE 11-2.
P/N 28902 CSAT3 Sonic Wick Spares Kit contents
11.2 Calibration
The CSAT3 is calibrated over the temperature range of -30° to +50°C
(standard) or -40° to +40°C (cold shifted).
The CSAT3 may or may not make
measurements outside the calibration range.
Any measurements taken outside
the calibration range will be suspect.
The CSAT3 does not require any field
calibration.
The CSAT3 electronics box contains unique calibration
information for its respective sensor head.
Do not
mismatch CSAT3 sensor heads and electronics.
Doing
so will result in erroneous wind and speed of sound
measurements.
If the CSAT3 requires a calibration, it will develop a wind offset greater than
the specifications, or it will set diagnostic flags, under dry conditions with little
to no wind and with no obstruction in the ultra sonic paths.
CSAT3s running
embedded code version 4 will develop the offset first and then possibly set
diagnostic flags under dry conditions.
CSAT3s running embedded code
version 3 will set diagnostic flags before a wind offset develops.
11.2.1 Cold Shifted Calibration
A CSAT3 with a cold shifted calibration is calibrated over the temperature of
-40° to +40°C. To improve the speed of sound reporting resolution, the
CSAT3 sends the speed of sound minus an offset to a datalogger via the SDM
interface or a PC via the RS-232 interface. The data acquisition system must
add the appropriate offset to determine the speed of sound. For the standard
temperature range the offset 340 m s
-1
. This offset is added by the
CSAT3()/SDM-CSAT3 (P107) instruction Command/Option 90, 91, 98, and
99. For the cold shifted calibration range, the offset is 337 m s
-1
.
WARNING
39