Campbell CSAT3, Instruction Manual

Page: 10 / 72

CSAT3 Three Dimensional Sonic Anemometer
2
to apply the speed of sound correction described by Liu et al., 2001. The
CSAT3 can be configured to make a single measurement per trigger or
multiple measurements that are centered around the trigger (oversampled).
OUTPUTS: u
x
, u
y
, u
z
, and c (u
x
, u
y
, u
z
, are orthogonal wind components
referenced to the anemometer head; c is the speed of sound)
SPEED OF SOUND: determined from 3 acoustic paths; corrected for
crosswind effects
MEASUREMENT RATE: programmable from 1 to 60 Hz, instantaneous
measurements; two oversampled modes are block averaged to either 20 Hz or
10 Hz
MEASUREMENT RESOLUTION: u
x
and u
y
are 1 mm s
-1
rms; u
z
is
0.5 mm s
-1
rms; c is 15 mm s
-1
(0.025
°
C) with embedded code version 4
(standard) [c is 1 mm s
-1
(0.002
°
C) with embedded code version 3]. Values are
the standard deviations of instantaneous measurements made of a constant
signal. The noise is unaffected by the sample rate.
OPERATING TEMPERATURE RANGE: -30
°
to 50
°
C (standard); -40
°
to
40
°
C (cold shifted)
ACCURACY (-30
°
to 50
°
C and -40
°
to 40
°
C operating range; wind speed < 30
m s
-1
; azimuth angles between
±
170
°
):
Offset Error:
u
x
, u
y
: <
±
8 cm s
-1
u
z
: <
±
4 cm s
-1
Gain Error:
Wind vector within
±
5
°
of horizontal <
±
2 percent of reading
Wind vector within
±
10
°
of horizontal <
±
3 percent of reading
Wind vector within
±
20
°
of horizontal <
±
6 percent of reading
2.2 Output Signals
The CSAT3 can output data to a data retrieval system using any of the
following communications: SDM (Synchronous Device for Measurement),
RS-232, or analog output. All the output signals have a two scan delay.
DIGITAL SDM: A Campbell Scientific, Inc. 33300 bps serial interface for
datalogger/sensor communication
Data type: 2-byte integer per output plus 2-byte diagnostic and 2-byte
configuration parameter
DIGITAL RS-232: Baud rate: 9600 bps or 19200 bps
Data type: 2-byte integer per output plus 2-byte diagnostic
ANALOG: Number of outputs: 4
Voltage range:
±
5 V
Number of bits: 12