CSAT3A 3-D Sonic Anemometer, Head Only
Precision Measurements
Best instrument for flux and other high-level turbulence research projects
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported

Overview

The CSAT3A 3-D Sonic Anemometer is the 3-D 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 50 Hz. The CSAT3A head is operated by the EC100 electronics, which also control either an EC150 or EC155 gas analyzer.

Measurements can be triggered from two sources:

  • Data logger’s SDM command
  • EC100’s internal clock

The SDM protocol supports a group trigger for synchronizing multiple CSAT3As.

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Benefits and Features

  • New conformal coating helps protect sonic transducers in corrosive environments
  • Innovative design provides precision turbulence measurements with minimal flow distortion
  • Usually combined with EC150 or EC155 gas analyzers giving near complete colocation for eddy-covariance measurements
  • Compatible with most Campbell Scientific data loggers
  • Measurements can be used to calculate momentum flux and friction velocity
  • Campbell Scientific’s fine wire thermocouples are an option for fast-response temperature measurements
  • Field rugged
  • Innovative signal processing and transducer wicks considerably improve performance of the anemometer during rain events
  • Sealed sonic transducers and electronics

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Detailed Description

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.


Specifications

Measurement Path Length
  • 10.0 cm (3.94 in.) vertical
  • 5.8 cm (2.3 in.) horizontal
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
Current
  • 200 mA (60 Hz measurement rate)
  • 100 mA (20 Hz measurement rate)
Digital SDM Output Signal CSI 33.3 k baud serial interface for data logger/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)

Measurements

Outputs 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
Measurement Resolution
  • Resolution values are for instantaneous measurements made on a constant signal; noise is not affected by sample rate.
  • 1 mm/s rms (ux, uy)
  • 0.5 mm/s rms (uz)
  • 15 mm/s (0.025°C) rms (c)
Offset Error
  • Offset error and gain error values assume the -30° to +50°C range, wind speeds of < 30 m/s, and wind angles between ±170°.
  • < ±8.0 cm/s (ux, uy)
  • < ±4.0 cm/s (uz)
Gain Error
  • Offset error and gain error values assume the -30° to +50°C range, wind speeds of < 30 m/s, and wind angles between ±170°.
  • < ±2% of reading (wind vector within ±5° of horizontal)
  • < ±3% of reading (wind vector within ±10° of horizontal)
  • < ±6% of reading (wind vector within ±20° of horizontal)
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).

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Data Loggers

Compatible Note
CR1000 (retired)
CR200X (retired)
CR206X (retired)
CR295X (retired)
CR3000 (retired)
CR5000 (retired)
CR800 (retired)
CR850 (retired)
CR9000X (retired)

FAQs for

Number of FAQs related to CSAT3A: 22

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  1. The CSAT3/3A/3AH calibration applies a correction for transducer delay over temperature. Transducer delays cause an offset in the wind speed measurement, and to a lesser extent, an offset in the speed of sound measurement.

    The CSAT3/3A/3AH speed of sound easement is corrected for the effects of wind blowing normal to the sonic path.

  2. The CSAT3/3A/3H is compatible with three output signals: analog, RS-232, and Synchronous Device for Measurement (SDM). The sonic anemometer can be interfaced to any data-acquisition system that is compatible with analog measurements or RS-232 serial communications. SDM is used with Campbell Scientific data loggers.

  3. The sensors used in the eddy-covariance application are not compatible with SCWin. An open-path eddy-covariance program is available for purchase as pn 18442, CRBasic Basic Eddy Covariance Program. This is the program without energy balance sensors. Also available is pn 18443, CRBasic Extended Eddy Covariance Program, with energy balance sensors. To order a custom configured program, contact the Environmental Group for assistance.

  4. 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.

  5. Yes. The bubble level can be replaced in the field using pn 31962, 1-Ring Replacement Bubble Level with Mounting Bumper and Hardware.

  6. The CSAT3A, CSAT3AH, CSAT3B, and CSAT3BH—like other sonic anemometers—measure wind speed along the sonic path using ultrasonic signals. If the salt spray blocks the sonic path, the sonic anemometer will not be able to make measurements. The same is true if a thick layer of salt is deposited on the transducer faces.

  7. 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.

  8. No. The offset is a function of temperature and time. Once a year, spot-check the sonic anemometer wind offset using the procedure outlined in the CSAT3B instruction manual. If the measured offset is outside the specification, return the sensor to the factory for calibration. To request a return material authorization (RMA) number, follow the steps listed on our Repair and Calibration page. 

  9. The sonic anemometer offset specification is ±8 cm/s. Therefore, it cannot be used in an application where the expected wind speed is in the range of ±5 cm/s.

  10. 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.