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This product is no longer available and has been replaced by: CSAT3B.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
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Overview

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 data loggers

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Technical 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.

Specifications

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
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 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)

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.
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

Analog
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)

Compatibility

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

Dataloggers

Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR216X (retired)
CR300
CR3000
CR5000 (retired)
CR6
CR800 (retired)
CR850 (retired)
CR9000X (retired)

Additional Compatibility Information

Data Logger Considerations

Required Operating Systems or PROMs
Data Logger Model Data Logger 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

Downloads

CSAT3 (567 KB) 24-03-1998

PC support software for monitoring and configuring the CSAT3.

FAQs for

Number of FAQs related to CSAT3: 10

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  1. 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.

  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. 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.

  4. Are there any corrections to the raw data (not the average data) obtained by the CSAT3/3A/3AH?

    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.

  5. Does the head of the CSAT3 need to be matched with its electronic box?

    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.)

  6. What are the mounting options for the CSAT3?

    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.

  7. 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.

  8. Are there any data logger programming changes that must be made to a program when using a long Synchronous Device for Measurement (SDM) cable with a CSAT3?

    With long cable lengths, monitor the SDM data collected from the CSAT3. If the CSAT3 diagnostic word is 61441 or NAN, there are SDM communications errors. If the SDM bit period is increased, SDM communications should be restored. Use the SDMSpeed() instruction to change the SDM bit period. Use the following values for the listed data loggers:

    • CR3000: 50
    • CR800, CR850, or CR1000: 100
    • CR5000: 90
  9. How is sensible heat flux measured using a CSAT3/3A/3H and an FW05?

    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.

  10. What is the absolute accuracy of the speed of sound measurement in the CSAT3/3A/3AH?

    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.

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