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 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.

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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.

Dataloggers

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 CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH well suited for all environments?

    The CSAT3A, CSAT3AH, CSAT3B, and CSAT3BH have been optimized for most terrestrial applications. If the sonic anemometer is to be used in a marine environment or in an environment where it is exposed to corrosive chemicals (for example, sulfur-containing compounds in viticulture), expect the sonic transducers to age more quickly and require replacement sooner than a unit deployed in an inland, chemical-free environment. Campbell Scientific offers a conformal coating option with our sonics to help alleviate corrosion; if your application poses a corrosive risk, consider adding this coating to your transducers. If possible, mount the sonic anemometer in a way that reduces exposure to saltwater spray/splash and/or corrosive chemicals. For applications that experience frozen precipitation, the heated versions of the CSAT3A and CSAT3B may be better suited.

  2. 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.

  3. 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.

  4. Is the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH anemometer measurement limited by precipitation?

    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.

  5. 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. 

  6. 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.

  7. 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.

  8. How sensitive are the CSAT3A, CSAT3AH, CSAT3B, and CSAT3BH velocity measurements to sea spray in periods of high wind speed?

    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.

  9. 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. 

  10. Can the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH be used in low-speed conditions, such as less than 5 cm/s? If so, what are the resolution and accuracy at these low speeds?

    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.

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