A faster measurement sees a different wind
Turbulence and flux research requires three-dimensional wind measurements at high sampling rates to capture the rapid air movements that transport heat, moisture and gases. Gill Research anemometers sample at 50 or 100 Hz for applications such as eddy covariance, while WindMaster provides three-axis wind measurement for a broader range of research and engineering applications.
What does turbulence and flux measurement need from an anemometer?
Turbulence and flux measurement needs all three wind components, sampled fast enough to resolve eddies that last fractions of a second, from a sensor head that disturbs the airflow as little as possible. Averaged readings smooth those fluctuations away. That is what separates research-grade 3-axis anemometers, such as the Gill R3 and HS range, from operational wind sensors.
The atmosphere transports heat, water vapour and carbon dioxide through turbulent air movements known as eddies. These fluctuations can occur over fractions of a second.
Measurements averaged over longer intervals can miss important fluctuations, limiting the detail available for calculating turbulent fluxes. Capturing these movements requires three components to work together: measurement of all three wind components, a sampling rate suited to the research and a sensor head designed to minimise disturbance to the airflow.
These requirements distinguish research-grade anemometers from instruments designed primarily for operational wind monitoring.
Measurement requirements
High-rate 3-axis measurement is demanding on the instrument and on everything around it. Sampling rate, head geometry, alignment, data volume and calibration each affect the quality of a flux estimate, and the errors compound rather than cancel.
Getting the instrument right is the start; installation and processing decide the rest.
Sampling rate
The sampling rate determines how much detail can be captured in rapidly changing airflow. Gill Research models operate at 50 or 100 Hz, depending on the model, allowing researchers to resolve faster fluctuations than conventional low-rate measurements.
Relevant models: R3-50, R3-100, HS-50 and HS-100.
Sensor-head design
The geometry of an ultrasonic anemometer affects how it interacts with the airflow. Transducer arms can disturb or shadow the flow, with particular implications for vertical wind measurements. The HS range uses a horizontal head designed for applications requiring careful measurement of vertical flow.
Relevant models: HS-50 and HS-100.
Alignment
Accurate vertical wind measurement is essential for flux calculations. Sensor tilt can introduce horizontal wind into the measured vertical component, potentially biasing the result. The HS range includes a built-in inclinometer to support alignment.
Relevant models: HS-50 and HS-100.
Individual calibration
Research applications require confidence in the instrument’s measurement performance. Individual calibration provides instrument-specific calibration data rather than relying solely on calibration by type.
Research range: Individual calibration as standard.
Measurement options
The appropriate anemometer depends on the research objective, required wind components, sampling rate and installation conditions.
Two-axis ultrasonic anemometers for operational wind measurement. Measure horizontal wind speed and direction. These instruments are suited to applications where routine wind measurement is required rather than high-rate, three-dimensional turbulence data.
WindMaster for general-purpose three-axis measurement. Measures three wind components for applications including building control, wind-site surveys, airflow studies and OEM integration. Output rates depend on the model and configuration, with options up to 32 Hz.
Gill Research range for high-rate turbulence and flux measurement. R3 and HS models sample at 50 or 100 Hz for applications such as eddy covariance and detailed turbulence research. The symmetrical R3 head and horizontal HS head offer different configurations for research requirements.
| Consideration |  Two-axis ultrasonic |  WindMaster |  Research range: R3 and HS |
|---|---|---|---|
| Wind components | Horizontal speed and direction | Three components | Three components |
| Output rate | Up to a few Hz, depending on model | Up to 32 Hz | 50 or 100 Hz |
| Head design | Reflector or open head, depending on model | Symmetrical | Symmetrical R3 or horizontal HS |
| Wind speed | Up to 90 m/s, depending on model | 0 to 50 m/s; WindMaster Pro to 65 m/s | 0 to 45 m/s |
| Typical applications | Operational wind monitoring | Building control, site surveys and airflow studies | Eddy covariance, flux and turbulence research |
The Research range is designed for measurement accuracy and high sampling rates, rather than extreme wind-speed applications. Where the priority is measuring high winds rather than resolving turbulence, a different sensor may be more appropriate.
System considerations
Data volume
A 100 Hz sampling rate generates twice as many samples as 50 Hz over the same period. Higher rates increase data volumes and processing requirements, so the choice should reflect the scientific objectives.
Maximum wind speed
The Research range measures wind speeds up to 45 m/s. Applications involving more extreme wind speeds may require a different instrument, depending on the measurement objectives.
Data interfaces
RS422 is the native interface. RS232 or analogue output requires the appropriate PCI or PCIA interface. Confirm interface requirements and compatibility with the data acquisition system during specification.
Operating temperature
Operating temperature varies across the Research range. HS-100 operates from 0 to +50°C, while R3-50, R3-100 and HS-50 operate from -40 to +60°C. Check the specification of the individual model against the expected site conditions.
Gill products for turbulence and flux measurement
R3-50 and R3-100
Symmetrical-head research anemometers
High-rate three-axis wind measurement for research applications, with PRT and analogue input options.
HS-50 and HS-100
Horizontal-head research anemometers
A horizontal stainless-steel head for applications requiring careful measurement of vertical airflow. The built-in inclinometer supports alignment, while six analogue inputs provide additional integration options.
WindMaster
General-purpose three-axis anemometer
Measures three wind components for building control, wind-site surveys, airflow studies and OEM integration.
insight
How eddy covariance works
Eddy covariance estimates the vertical flux of a quantity, such as heat, water vapour or carbon dioxide, by measuring the covariance between fluctuations in vertical wind and fluctuations in that quantity.
When vertical air movement is correlated with changes in temperature, humidity or gas concentration, the relationship can be used to estimate the net vertical transport over a measurement period. Both signals must be captured at a sufficiently high rate and synchronised accurately, which makes sampling frequency and timing important to the result.
The vertical wind component must also be measured reliably. Sensor tilt or head-induced flow distortion can introduce errors into the vertical signal and bias the calculated flux. The HS horizontal head and built-in inclinometer address aspects of this measurement challenge.
The anemometer is one part of the measurement system. The scalar sensor, signal synchronisation, data acquisition, sensor alignment and processing all contribute to the quality of the final flux estimate.
The full explanation is in How does an ultrasonic wind sensor work?
Related applications and research
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Speak to our team
Tell us what you need to measure, where and under what conditions. We’ll help you work out the appropriate approach.
Frequently asked questions
An eddy covariance anemometer measures three-dimensional wind fluctuations used to calculate exchanges of heat, water vapour and gases between the surface and the atmosphere. The method combines vertical wind measurements with a synchronised measurement of the quantity being studied. Gill R3 and HS research anemometers are designed for high-rate wind measurement in applications including eddy covariance and turbulence research.
The required sampling rate depends on the research objectives, site conditions, measurement system and turbulent fluctuations that need to be resolved. Gill offers research anemometers with output rates of 50 Hz and 100 Hz. A higher sampling rate generates more data, so the appropriate specification should be determined by the requirements of the study.
Both R3 and HS are research-grade, three-axis ultrasonic anemometers available at 50 Hz or 100 Hz. The R3 has a symmetrical sensor head for general turbulence and flux research. The HS has a horizontal head designed to minimise flow disturbance when measuring vertical airflow, plus a built-in inclinometer to assist alignment and six analogue inputs.
WindMaster provides three-axis wind measurement for applications such as building control, wind-site surveys and airflow studies, with output rates up to 32 Hz depending on the model. The Research range offers 50 Hz or 100 Hz sampling for applications requiring higher-rate wind data, including eddy covariance and detailed turbulence analysis.
Eddy covariance calculations use the relationship between fluctuations in vertical wind and fluctuations in the measured scalar, such as gas concentration or temperature. Sensor tilt can introduce horizontal wind into the vertical component and bias the calculated flux. Sensor-head design, alignment and installation therefore matter to measurement quality.
No. A three-axis anemometer measures wind components and, depending on the model, additional parameters such as sonic temperature. Calculating heat or gas flux requires the wind data to be combined with appropriate scalar measurements, synchronised data acquisition and processing.
Gill Research anemometers support high-rate three-axis wind data, with interface and analogue-input options depending on the model and configuration. RS422 is the native interface; RS232 or analogue output may require an appropriate interface. Confirm the exact requirements against the individual model datasheet before specifying the complete system.