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Table 7-1: Overview of CSAT3BH operating modes
Mode
Measurement Trigger
Filters
Output Prompt
Source
Rate
Enabled
Bandwidth (Hz)
Source
Rate
0
Data logger 1 to 100 Hz
1/
No
-
Data logger
1 to 100 Hz
1/
1
CSAT3BH
100 Hz
Yes
5, 10, 25
Data logger
1 to 100 Hz
1/
2
CSAT3BH
100 Hz
No
-
CSAT3BH 10, 20, 50, 100 Hz
3
CSAT3BH
100 Hz
Yes
5, 10, 25
CSAT3BH 10, 20, 50, 100 Hz
1/
The exact rate is determined by the scan interval set in the CRBasic program of the data logger.
NOTE:
Data logger prompted output using Mode 0 requires use of SDM or CPI communications.
Data logger prompted output using Mode 1 requires CPI communications (SDM not
compatible with bandwidth filters). The options for unprompted output to a computer
require use of RS-485 or USB communications.
7.3.1 Measurement trigger
A measurement trigger is the actual command to initiate a sonic measurement and can be driven
by either a data logger or the CSAT3BH internal timer. If the trigger is given by a data logger as in
Mode 0, then no data filtering is done (bandwidth is wide open) since each trigger will initiate a
single new measurement (single-measurement regime). The data logger can trigger
measurements at rates from 1 to 100 Hz. If the trigger is given by the internal CSAT3BH timer as in
Modes 1 through 3, the measurements will be self-triggered at a rate of 100 Hz. This results in an
oversampled measurement regime where the 100 Hz samples may be optionally processed
through a filter before being down sampled or decimated and output.
NOTE:
If a data logger fails to provide a trigger and the CSAT3BH has not been configured for
unprompted output, the CSAT3BH will enter into a lost-trigger state where it will output
measurements at 1 Hz based on its internal timer. If the CSAT3BH is in a lost-trigger state
while connected with
Device Configuration Utility
, real-time anemometer data will flash on
the screen at one-second intervals, and the LED Status light on the CSAT3BH head will flash
red. This is an indication that the settings should be checked. It does not indicate a problem
with the CSAT3BH hardware. Once a trigger is received by the CSAT3BH, or once
unprompted output is enabled, normal operation will ensue.
CSAT3BH Three-Dimensional Heated Sonic Anemometer
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