Campbell Scientific’s CSAT3 3D Sonic Anemometer is the 3D sonic anemometer of choice for eddy-covariance measurements. It has an aerodynamic design, a 10 cm vertical measurement path, operates in a pulsed acoustic mode, and withstands exposure to harsh weather conditions. Three orthogonal wind components (ux, uy, uz) and the speed of sound (c) are measured and output at a maximum rate of 60 Hz. Analog outputs and two types of digital outputs are provided.
Measurements can be triggered from three sources:
Datalogger’s SDM command
CSAT3’s internal clock
PC-generated RS-232 command
The SDM protocol supports a group trigger for synchronizing multiple CSAT3s.
Benefits and Features
l Innovative design provides precision turbulence measurements with minimal flow distortion
l Can be combined with EC150 or EC155 gas analyzers giving near complete colocation for eddy-covariance measurements
l Compatible with most Campbell Scientific dataloggers
l Measurements can be used to calculate momentum flux and friction velocity
l Campbell Scientific’s fine wire thermocouples are an option for fast-response temperature measurements
l Field rugged
l Rain: Innovative signal processing and transducer wicks considerably improves performance of the anemometer duringrain events
l Sealed sonic transducers and electronics
Specifications
Measurements
l Outputs: ux, uy, uz, c (ux, uy, uz are wind components referenced to the anemometer axes; c is speed of sound)
l Speed of Sound: Determined from three acoustic paths; corrected for crosswind effects
l Measurement Rate: programmable from 1 to 60 Hz, instantaneous measurements; two over-sampled modes are block averaged to either 20 Hz or 10 Hz
Measurement Precision RMSa
l ux, uy: 1 mm s-1 rms
l uz: 0.5 mm s-1 rms
l c: 15 mm s-1 (0.025°C) rms
l Wind Direction: 0.06° rms
Accuracyb
l Offset error: <±8.0 cm s-1 (ux, uy), <±4.0 cm s-1 (uz)
l Gain Error
Wind Vector within ±5° of horizontal: <±2% of reading
Wind Vector within ±10° of horizontal: <±3% of reading
Wind Vector within ±20° of horizontal: <±6% of reading
l Wind Direction: ±0.7° at 1 m s-1 for horizontal wind
Output Signals
l Digital SDM: CSI 33.3 k bps serial interface for datalogger/ sensor communication. Data type is 2 B integer per output plus 2 B diagnostic
Digital RS-232
l Baud rate: 9600, 19200 bps
l Data type: 2 B integer per output plus 2 B diagnostic
Analog
l Number of outputs: 4
l Voltage range: ±5 V
l Number of bits: 12
Reporting Range
l Analog Outputs:
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Output
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Reporting Range
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LSB
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ux, uy
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±30 m s-1, ±60 m s-1
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15 mm s-1, 30 mm s-1
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uZ
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±8 m s-1
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4 mm s-1
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c
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300 to 366 m s-1 (-50° to +60°C)
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16 mm s-1 (0.026°C)
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SDM and RS-232 Digital Outputs
l Full scale wind: ±65.535 m s-1 autoranging between four ranges; least significant bit is 0.25 to 2 mm s-1
l Speed of Sound: 300 to 366 m s-1 (-50° to +60°C); least significant bit is 1 mm s-1 (0.002°C)
Physical Description
l Measurement Path Length: 10.0 cm vertical; 5.8 cm horizontal
l Path Angle from Horizontal: 60 degrees
l Transducer: 0.64 cm diameter
l Transducer Mounting Arms: 0.84 cm diameter
l Support Arms: 1.59 cm diameter
Dimensions
l Anemometer head: 47.3 cm (l) x 42.4 cm (h)
l Electronics box: 26 x 16 x 9 cm
Weight
l Anemometer head: 1.7 kg (3.7 lb)
l Electronics box: 3.8 kg (8.4 lb)
Materials
l Anemometer head: stainless steel tubing
l Electronics box: cast aluminum
Environmental
l Operating Temperature: -30° to +50°C
Power Requirements
l Voltage Supply: 10 to 16 Vdc
l Current: 200 mA @ 60 Hz measurement rate; 100 mA @ 20 Hz measurement rate
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