CSAT3B 3-D Sonic Anemometer with Integrated Electronics
Precision Measurements
Designed for flux and other turbulence research projects
weather applications water applications energy applications gas flux and turbulence applications infrastructure applications soil applications

Overview

Campbell Scientific’s CSAT3B 3-D Sonic Anemometer is an update and replacement to the original CSAT3, and remains 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 sonic temperature (Ts) are measured and output at a maximum rate of 100 Hz.

The most conspicuous innovation of the new design is the elimination of the electronics box. Instead, the electronics are packaged inside the mounting block of the CSAT3B head. This design feature makes installation easier and offers greater flexibility in instrument placement.

Measurements can be triggered from three sources:

  • Data logger SDM command
  • Data logger CPI command
  • CSAT3B internal clock

The SDM and CPI protocols both support mechanisms for synchronizing multiple CSAT3Bs.

Benefits and Features

  • New conformal coating helps protect sonic transducers in corrosive environments
  • Integrated electronics that provide easy mounting of a single piece of hardware
  • Integrated inclinometer
  • High-precision measurements ideal for turbulence and eddy-covariance studies
  • An improved design with a thin, aerodynamic support strut close to the ends of the sensor arms, creating greater rigidity and improved accuracy of sonic temperature
  • Data logger sampling supported for any frequency between 1 and 100 Hz
  • New CPI communications for more robust, higher bandwidth measurements
  • Multiple communication options including SDM, CPI, USB, and RS-485
  • Internal temperature and humidity measurements with easily replaced desiccant
  • Version 5 algorithm for calculating data outputs; combines the signal sensitivity of version 3 with the rain performance of version 4
  • Includes options to filter high frequencies for applications requiring analysis of non-aliased spectra

Images

Specifications

Sensor 3-dimensional sonic anemometer
Measurement Description Highest-quality wind speed and direction
Operating Temperature Range -40 to +50°C (equivalent to 305 to 368 m s-1 in speed of sound)
Outputs ux, uy, uz, Ts (ux, uy, uz are wind components referenced to the anemometer axes; Ts is sonic temperature in degrees Celsius.)
Signal Type/Output SDM, CPI, USB, RS-485
Speed of Sound Determined from three acoustic paths. (Corrected for crosswind effects.)
Wind Direction Range 2.5 to 357.5° in CSAT3B coordinate system (0 to 360° customized)
Range ± 65 m s–1 (full-scale wind)
Filter Bandwidths 5, 10, or 25 Hz
Measurement Path Length 10.0 cm (3.9 in.) vertical; 5.8 cm (2.3 in.) horizontal
Transducer Angle from Horizontal 60 degrees
Transducer Diameter 0.64 cm (0.25 in.)
Transducer Mounting Arm Diameter 0.84 cm (0.33 in.)
Support Arm Diameter 1.59 cm (0.63 in.)
Anemometer Head Weight 1.45 kg (3.2 lb)
Anemometer Dimensions 60.64 x 12.2 x 43.0 cm (23.87 x 4.8 x 16.9 in.)

Wind Accuracy
-NOTE- Accuracy specifications assume the following:
  • -40° to +50°C operating range
  • Wind speeds < 30 m s-1
  • Wind angles between ±170°
Maximum Offset Error < ±8.0 cm s-1 (ux, uy), < ±4.0 cm s-1 (uz)
Maximum Gain Error
  • < ±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)

Measurement Resolution
ux, uy 1 mm s-1 rms
uz 0.5 mm s-1 rms
Ts 0.002°C RMS (at 25°C)
Wind Direction < 0.058° (ux = uy ≤ 1 m s-1)

Measurement Rates
Data Logger Triggered 1 to 100 Hz
Unprompted Output (to PC) 10, 20, 50, or 100 Hz
Internal Self-Trigger Rate 100 Hz

Measurement Delay
Data Logger Triggered (no filter) 1 trigger period (1 scan interval)
Unprompted Output (no filter) 10 ms
Filtered Output (data-logger-prompted or unprompted to PC)
  • 795 ms (with 5 Hz bandwidth filter)
  • 395 ms (with 10 Hz bandwidth filter)
  • 155 ms (with 25 Hz bandwidth filter)

Internal Monitor Measurements
Update Rate 2 Hz
Inclinometer Accuracy ±1°
Relative Humidity Accuracy
  • ±3% (over 10 to 90% range)
  • ±7% (over 0 to 10% range)
  • ±7% (over 90 to 100 % range)
Board Temperature Accuracy ±2°C

SDM
-NOTE- Used for data-logger-based data acquisition.
Bit Period 10 µs to 1 ms
Cable Length
  • 7.6 m (25 ft) max (@ 10 µs bit period)
  • 76 m (250 ft) max (@ 1 ms bit period)
Address Range 1 to 14
Bus Clocks per Sample ~200

CPI
-NOTE- Used for data-logger-based data acquisition.
Baud Rate 50 kbps to 1 Mbps
Cable Length
  • 15 m (50 ft) max (@ 1 Mbps)
  • 122 m (400 ft) max (@ 250 kbps)
  • 853 m (2800 ft) max (@ 50 kbps)
Address Range 1 to 120
Bus Clocks per Sample ~300

RS-485
-NOTE- Used for configuration or PC-based data acquisition.
Baud Rate 9.6 kbps to 115.2 kbps
Cable Length
  • 305 m (1000 ft) max (@ 115.2 kbps)
  • 610 m (2000 ft) max (@ 9.6 kbps)
Bus Clocks per Sample ~500 (ASCII formatted)

USB
-NOTE- Used for configuration or PC-based data acquisition.
Connection Speed USB 2.0 full speed 12 Mbps
Cable Length 5 m (16.4 ft) maximum

Power Requirements
Voltage Supply 9.5 to 32 Vdc
Current at 10 Hz Measurement Rate
  • 110 mA (@ 12 Vdc)
  • 65 mA (@ 24 Vdc)
Current at 100 Hz Measurement Rate
  • 145 mA (@ 12 Vdc)
  • 80 mA (@ 24 Vdc)

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)
CR1000X
CR300
CR3000 (retired)
CR310
CR350
CR6
CR800 (retired)
CR850 (retired)
CR850 (retired)

Downloads

CSAT3B Example Programs v.1 (4 kB) 20-10-2020

Three example programs. 

Simple SDM Program: SDM communications are used to collect data from a single CSAT3B.

Simple CPI Program: CPI communications are used to collect data from a single CSAT3B.

Advanced CPI Program: A single CSAT3B is properly configured and CPI communications are used to collect the data.

CSAT3B OS v.3.02 (548 KB) 14-10-2019

Current CSAT3B Operating System.

View Revision History

CPI Calculator v.1.0 (2.49 MB) 06-07-2016

The CPI Calculator is a downloadable Microsoft Excel spreadsheet used to estimate the usage and capacity of a CPI network.  The calculator provides an overview on CPI devices including the CDM-A108, CDM-A116, CDM-VW300, CDM-VW305, and the CSAT3B.  The calculator can also estimate the measurement speed of the CDM-A108 and CDM-A116 based on the number of channels and measurement parameters.

 

The CPI Calculator is an estimation tool and will help you better understand and design CPI networks by considering the following:

  1. What is the capability of each CDM or CPI device
  2. What is the CPI network capacity
  3. How much of the CPI capacity are the CDMs or CPI devices using

 

Frequently Asked Questions

Number of FAQs related to CSAT3B: 16

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  1. Can a CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH be used to measure wind flow angle, horizontal angle, and wind speed for the purpose of power curve testing?

    The sonic anemometer measures three-dimensional wind in a right-handed Cartesian coordinate system. From these measurements, use trigonometry to compute the wind flow angle, horizontal angle, and wind speed.

  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. 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.

  5. 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.

  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. 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.

  8. Is the crosswind correction applied to the raw data of the CSAT3A, CSAT3AH, CSAT3B, or CSAT3BH?

    Yes. The effect of wind blowing normal to the sonic path on the speed of sound (sonic temperature) is corrected for in the electronics of the sonic anemometer. The corrections to the speed of sound (sonic temperature) described in

    Liu, H., Peters, G., and Foken, T.:  2001, “New Equations for Sonic Temperature Variance and Buoyancy Heat Flux with an Omnidirectional Sonic Anemometer,” Boundary-Layer Meteorol., 100, 459-468.
     
    Schotanus, P., Nieuwstadt, F. T. M., and de Bruin, H. A. R.:  1983, “Temperature Measurement with a Sonic Anemometer and its Application to Heat and Moisture Fluxes,” Boundary-Layer Meteorol., 26, 81-93.

    need not be applied to the sonic anemometer speed of sound (sonic temperature) data.

  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 CSAT3B or CSAT3BH measurement frequency be changed? If so, what frequencies are supported by these sensors?

    Yes. The CSAT3B and CSAT3BH measurement frequency can be changed by the user. The user can either choose a prompted or unprompted output rate. The prompted output rate is based on the scan interval of the data logger, which must be an integer. Therefore, the measurement frequencies supported would be 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, and 100 Hz. The unprompted output rate allowed is 10, 20, 50, and 100 Hz.

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