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

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

Images

CSAT3A lower transducer assembly top view

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

Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Data Loggers

Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR206X (retired)
CR211X (retired)
CR216X (retired)
CR295X (retired)
CR3000 (retired)
CR5000 (retired)
CR800 (retired)
CR850 (retired)
CR9000X (retired)

Frequently Asked Questions

Number of FAQs related to CSAT3A: 22

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  1. Is the offset relatively constant for a single CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH?

    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. 

  2. Is the CSAT3/3A/3AH only compatible with Campbell Scientific data loggers?

    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. If the temperature drops below -30°C, is that a problem for a CSAT3A or CSAT3B?

    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.

  4. Can the bubble level on the CSAT3/3A/3H be replaced?

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

  5. What should be done if the CSAT3/3A/3AH cannot be found in the Short Cut list of sensors?

    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.

  6. Is there a way to determine the time at which the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH started reporting data with sub-second precision?

    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.

  7. What are the calibration procedures for the CSAT3A, CSAT3AH, CSAT3B, and CSAT3BH, and how are they traceable to the National Institute of Standards and Technology (NIST)?

    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.

  8. If the polymer coating at the ends of the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH transducers starts coming off, is that a problem?

    Yes. If the matching layer is damaged or missing, return the sonic anemometer to the factory for repair. Follow the steps listed on our Repair and Calibration page to request a return material authorization (RMA) number. 

  9. Can the CSAT3/3A/3AH give a time stamp with each measurement value?

    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.

  10. Are there any mounting options for the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH that lend themselves to frequent repositioning?

    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.

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