This product is no longer available and has been replaced by: CSAT3B. Some accessories, replacement parts, or services may still be available.
CSAT3 3-D Sonic Anemometer
Precision Measurements
Best instrument for flux and
other high-level turbulence
research projects
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications


The CSAT3 is a three-dimensional sonic anemometer that measures three orthogonal wind components and the speed of sound. In eddy covariance systems, it can measure the turbulent fluctuations of horizontal and vertical wind. These measurements are then used to calculate momentum flux and friction velocity. This sonic anemometer can also provide average horizontal wind speed and direction measurements. The CSAT3 comes with 25 ft cables.

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Benefits and Features

  • Provides precision turbulence measurements with minimal flow distortion
  • FW05 fine wire thermocouple (12.7 μm diameter) is available as an option for fast response temperature measurements
  • Withstands exposure to harsh weather conditions
  • Measurements can be used to calculate momentum flux and friction velocity
  • Compatible with most Campbell Scientific dataloggers

Whenever possible, use the CSAT3B (the CSAT3's replacement) instead. 


Detailed Description

The CSAT3 has a 10 cm vertical measurement path and operates in a pulsed acoustic mode. The 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 from the CSAT3’s internal clock, the PC-generated RS-232 command, or the datalogger’s SDM command. The SDM protocol supports a group trigger for synchronizing multiple CSAT3s.

The FW05 fine wire thermocouple (12.7 μm diameter) is available as an option for fast response temperature measurements.


Measurement Path Length
  • 10.0 cm (3.94 in.) vertical
  • 5.8 cm (2.28 in.) horizontal
Path Angle from Horizontal 60°
Construction Sealed sonic transducers and electronics
Anemometer Head Materials Stainless-steel tubing
Electronics Box Materials Cast aluminum
Operating Temperature Range -30° to +50°C
Voltage Supply 10 to 16 Vdc
  • 200 mA (60 Hz measurement rate)
  • 100 mA (20 Hz measurement rate)
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 Arms Diameter 1.59 cm (0.63 in.)
Transducer Diameter 0.64 cm (0.25 in.)
Transducer Mounting Fingers Diameter 0.84 cm (0.33 in.)
Cable Length 7.62 m (25 ft)
Anemometer Head Dimensions 47.3 x 42.4 cm (18.6 x 16.7 in.)
Anemometer Head Weight 1.7 kg (3.7 lb)
Electronics Box Dimensions 26 x 16 x 9 cm (10.24 x 6.3 x 3.54 in.)
Electronics Box Weight 3.8 kg (8.4 lb)


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.
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)
  • 0.06° rms (wind direction)
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)
Wind Direction Accuracy ±0.7° at 1 m/s (for horizontal wind)
Rain Innovative ultrasonic signal processing and user-installable wicks considerably improve the performance of the anemometer under all rain events.

Digital RS-232 Output Signal

Baud Rate 9600, 19200 bps
Data Type 2-byte integer per output plus 2-byte diagnostic


Number of Outputs 4
Voltage Range ±5 V
Number of Bits 12

SDM & RS-232 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).

Analog Outputs Reporting Range

ux ±30 m s-1, ±60 m s-1
uy ±30 m s-1, ±60 m s-1
uz ±8 m s-1
c 300 to 366 m s-1 (-50 to +60°C)

Analog Outputs LSB

ux 15 mm s-1, 30 mm s-1
uy 15 mm s-1, 30 mm s-1
uz ±8 m s-1
c 16 mm s-1 (0.026°C)


Datalogger Considerations

Required Operating Systems or PROMs

Datalogger Model Datalogger Operating System (OS)
or PROMs Required
CSAT3 OS Required
21X 1K 6145-3, 6146-5, 10006-1 2.1 or higher
21X 2K 6148-5, 6149-7, 6070-64 2.1 or higher
CR800, CR850 All OS 3.0 or higher
CR10 2K 5954-396;
4K is a Library Special
2.1 or higher
CR10X OS 1.4 or higher 2.1 or higher
CR1000 All OS 3.0 or higher
CR23X All OS 2.1 or higher
CR3000 All OS 3.0 or higher
CR5000 All OS 3.0 or higher
CR9000 2.01 or higher 2.1 or higher
CR9000X All OS 2.1 or higher

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X CR6 CR300

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X


CSAT3 (567 KB) 03-24-1998

PC support software for monitoring and configuring the CSAT3.

Frequently Asked Questions

Number of FAQs related to CSAT3: 26

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  1. The CSAT3 has been optimized for most terrestrial applications. If the CSAT3 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. If possible, mount the CSAT3 in a way that reduces exposure to saltwater spray/splash and/or corrosive chemicals.

  2. No. The CSAT3 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 datalogger or a PC.

  3. No. The CSAT3 is a sensor. Time stamps are assigned to the CSAT3 data by the data acquisition system—typically a Campbell Scientific datalogger or PC.

  4. 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 Micrometeorology Flux group for assistance.

  5. The CSAT3 can be mounted on the end of a CM202, CM203, CM204, or CM206 crossarm, using the included CM250 Leveling Mounting Kit. Alternatively, the CSAT3 can mounted to a flat horizontal surface using a 3/8-16 stainless-steel bolt.

  6. Yes. If the matching layer is damaged or missing, return the CSAT3 to the factory for repair. Follow the steps listed on our Repair and Calibration page to request a returned material authorization (RMA) number. 

  7. Yes. The CSAT3 electronics contain unique calibration and sensor head geometry information. The sensor head and electronics are a matched set. (The serial number on the sensor head must match the electronics to make valid measurements.)

  8. The CSAT3, like other sonic anemometers, measures wind speed along the sonic path using ultrasonic signals. If the salt spray blocks the sonic path, the CSAT3 will not be able to make measurements. The same is true if a thick layer of salt is deposited on the transducer faces.

  9. No. The offset is a function of temperature and time. Once a year, spot-check the CSAT3 wind offset using the procedure outlined in the CSAT3 instruction manual. If the measured offset is outside the specification, return the CSAT3 to the factory for calibration. To request a returned material authorization (RMA) number, follow the steps listed on our Repair and Calibration page. 

  10. The CSAT3 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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