The CSAT3A sonic anemometer head is similar to the sensor head from the CSAT3 sonic anemometer, but its cable is modified to connect to the EC100 electronics. It is used as part of the EC150 open-path analyzer and the CPEC200 closed-path eddy-covariance system.
The CSAT3A is an optional component of an EC150 open-path or EC155 closed-path CO2/H2O gas analyzer. It attaches to a common mounting bracket and connects to the gas analyzer's EC100 electronics module.
|Measurement Path Length||
|Path Angle from Horizontal||60°|
|Construction||Sealed sonic transducers and electronics|
|Anemometer Head Materials||Stainless-steel tubing|
|Electronics Box Materials||Welded aluminum|
|Operating Temperature Range||-30° to +50°C|
|Voltage Supply||10 to 16 Vdc|
|Digital SDM Output Signal||CSI 33.3 k baud serial interface for datalogger/sensor communication. (Data type is 2-byte integer per output plus 2-byte diagnostic.)|
|Support Arm Diameter||1.59 cm (0.63 in.)|
|Transducer Diameter||0.64 cm (0.25 in.)|
|Transducer Mounting Arm Diameter||0.84 cm (0.33 in.)|
|Anemometer Head Dimensions||47.3 x 42.4 cm (18.6 x 16.7 in.)|
|Anemometer Head Weight||1.7 kg (3.7 lb)|
ux, uy, uz, c
(ux, uy, uz are wind components referenced to the anemometer axes; c is speed of sound.)
|Speed of Sound||Determined from three acoustic paths; corrected for crosswind effects.|
|Measurement Rate||Programmable from 1 to 60 Hz, instantaneous measurements. Two over-sampled modes are block averaged to either 20 Hz or 10 Hz.|
|Output Bandwidths||5, 10, 12.5, or 20 Hz|
|Output Rate||10, 20, 25, or 50 Hz|
|Rain||Innovative ultrasonic signal processing and user-installable wicks considerably improve the performance of the anemometer under all rain events.|
Digital USB and RS-485 Output Signal
|Baud Rate||230400 bps (maximum)|
|Data Type||Comma-delimited ASCII|
SDM, USB, & RS-485 Digital Outputs Reporting Range
|Full-Scale Wind||±65.535 m/s autoranging between four ranges (Least significant bit is 0.25 to 2 mm/s.)|
|Speed of Sound||300 to 366 m/s (-50° to +60°C) Least significant bit is 1 mm/s (0.002°C).|
Number of FAQs related to CSAT3A: 22
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No. The CSAT3/3A/3AH is a sensor. Time stamps are assigned to the sonic anemometer data by the data-acquisition system—typically a Campbell Scientific data logger or PC.
No. The sonic anemometer does not report time with the wind measurements. A time stamp will be assigned to the wind data by the data-acquisition system—either a data logger or a PC.
The sonic anemometer measures three-dimensional wind in a right-handed Cartesian coordinate system. From these measurements, use trigonometry to compute the wind flow angle, horizontal angle, and wind speed.
Campbell Scientific does not offer any mounting booms or hardware that enable easy and frequent positioning of the sonic anemometer sensor head. This type of hardware must be provided by the user.
Sensible heat flux is defined as the covariance of vertical wind and temperature fluctuations, measured with fast-response sensors. For more information, refer to a micrometeorology textbook.
The CSAT3A, CSAT3AH, CSAT3B, and CSAT3BH are calibrated over temperature for the effects of transducer delays on the wind speed, and to a lesser extent, for the speed of sound measurements.
There is no NIST-traceable standard for ultrasonic anemometers.
Ultrasonic anemometers are unable to make measurements if the sonic path is blocked. The path may become blocked by water that puddles on the lower transducer face or droplets that hang from the upper transducers. Sonic wicks, which come with all sonics, can be placed on the transducers to wick away moisture from the faces of the transducers. Ensure that these wicks are removed during cold conditions to prevent ice from building up around them.
The CSAT3/3A/3AH should not be used to measure absolute sonic temperature. Aside from the effects of water vapor in the sonic path, the speed of sound measurement is highly dependent on the ability of the sonic anemometer to maintain its geometry. A 0.2 mm change in the sonic path is equal to a 1°C change in the measured absolute sonic temperature at 25°C. This is equal to a 0.33% error in the absolute sonic temperature. The wind speed measurements are also dependent on the sonic path distance, but to a lesser degree.
Yes. The effect of wind blowing normal to the sonic path on the speed of sound (sonic temperature) is corrected for in the electronics of the sonic anemometer. The corrections to the speed of sound (sonic temperature) described in
|Liu, H., Peters, G., and Foken, T.: 2001, “New Equations for Sonic Temperature Variance and Buoyancy Heat Flux with an Omnidirectional Sonic Anemometer,” Boundary-Layer Meteorol., 100, 459-468.|
|Schotanus, P., Nieuwstadt, F. T. M., and de Bruin, H. A. R.: 1983, “Temperature Measurement with a Sonic Anemometer and its Application to Heat and Moisture Fluxes,” Boundary-Layer Meteorol., 26, 81-93.|
need not be applied to the sonic anemometer speed of sound (sonic temperature) data.
The CSAT3A or CSAT3B is calibrated over the temperature range of -30° to +50°C. The sonic anemometer operating temperature range can be shifted by 10 degrees to cover the range of -40° to +40°C. For low-temperature applications, it may be more appropriate to consider a heated version of our sonic anemometers.
The instrument will continue to operate outside the calibrated temperature range, until the signal becomes too weak; however, the proper calibration will not be applied to the measurements because the calibration file only spans the specified temperature range.