Campbell Scientific CSAT3 CSAT3 3-D Sonic Anemometer - Page 48

Test for Wind Offset

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CSAT3 Three Dimensional Sonic Anemometer The standard datalogger instruction reports either the speed of sound (c), option 90 or 99, or the sonic temperature (Ts), Command/Option 91 or 98, can not be used with a CSAT3 running a cold shifted calibration. Instead, use option 92 "Trigger and Get Wind & c-340 Data" or option 97 "Get Wind and c-340 Data After a Group Trigger" and then add 337 m s-1. To find Ts, use Equation 9 in Appendix C. 11.2.2 Test for Wind Offset To test wind offset on a CSAT3, create an environment were there is no wind. It is difficult to do this in the field, thus it is best to collect CSAT3 wind offset data in a field office or the lab. A zero wind environment can be created with a kitchen waste bin liner. Mount the head in the normal horizontal fashion, or hang the head from the block that supports the CSAT3 upper and lower arms. Do not lay the CAST3 head on its side or balance it on the transducers. Cover the CSAT3 head with a medium (13 gallon) kitchen waste bin liner. Fold, tape, or tie closed the opening of the liner to prevent air from moving in and out of the liner. Ensure that the liner does not obstruct any of the three CSAT3 sonic paths. Connect the CSAT3 power cable to a 12 Vdc power supply. Connect the CSAT3's RS-232 port to the PC's RS-232 port using the RS-232 cable that shipped with the CSAT3. This cable was originally located underneath the circular "cut out" in the CSAT3 case. Start the CSAT3 PC support software (CSAT32.EXE) to establish communications between the PC and the CSAT3. A copy of the software is available from the Campbell Scientific web site, in the Support|Downloads section. If successful communications are established, the "Status" window will report "Good Data". To prevent erroneous measurements due to ultra sonic reflection within the plastic bag, select a 1 Hz Measurement Rate (FIGURE 11-3). FIGURE 11-3. CSAT3 running at 1 Hz and successfully communicating with the CSAT3 Double click on the vertical axis and set it up as shown in FIGURE 11-4. Next, double click on the vertical axis label and set it up to report 2 significant digits (FIGURE 11-5). 40

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CSAT3 Three Dimensional Sonic Anemometer
The standard datalogger instruction reports either the speed of sound (c), option
90 or 99, or the sonic temperature (T
s
), Command/Option 91 or 98, can not be
used with a CSAT3 running a cold shifted calibration. Instead, use option 92
“Trigger and Get Wind & c-340 Data” or option 97 “Get Wind and c-340 Data
After a Group Trigger” and then add 337 m s
-1
. To find T
s
, use Equation 9 in
Appendix C.
11.2.2 Test for Wind Offset
To test wind offset on a CSAT3, create an environment were there is no wind.
It is difficult to do this in the field, thus it is best to collect CSAT3 wind offset
data in a field office or the lab. A zero wind environment can be created with a
kitchen waste bin liner.
Mount the head in the normal horizontal fashion, or hang the head from the
block that supports the CSAT3 upper and lower arms. Do not lay the CAST3
head on its side or balance it on the transducers.
Cover the CSAT3 head with a medium (13 gallon) kitchen waste bin liner.
Fold, tape, or tie closed the opening of the liner to prevent air from moving in
and out of the liner. Ensure that the liner does not obstruct any of the three
CSAT3 sonic paths.
Connect the CSAT3 power cable to a 12 Vdc power supply. Connect the
CSAT3’s RS-232 port to the PC’s RS-232 port using the RS-232 cable that
shipped with the CSAT3. This cable was originally located underneath the
circular “cut out” in the CSAT3 case.
Start the CSAT3 PC support software (CSAT32.EXE) to establish
communications between the PC and the CSAT3. A copy of the software is
available from the Campbell Scientific web site, in the Support|Downloads
section. If successful communications are established, the “Status” window
will report “Good Data”. To prevent erroneous measurements due to ultra
sonic reflection within the plastic bag, select a 1 Hz Measurement Rate
(FIGURE 11-3).
FIGURE 11-3.
CSAT3 running at 1 Hz and successfully communicating
with the CSAT3
Double click on the vertical axis and set it up as shown in FIGURE 11-4.
Next, double click on the vertical axis label and set it up to report 2 significant
digits (FIGURE 11-5).
40