Nothing to turn. That is the point.
An ultrasonic anemometer measures wind speed and direction by timing sound pulses between transducers, with no cups, vanes or bearings. That removes mechanical wear from the measurement. It does not remove siting, icing or flow distortion, which still need engineering. Gill ultrasonic ranges cover 2-axis and 3-axis wind.
How does a wind sensor measure without moving parts?
An ultrasonic wind sensor measures wind without moving parts by timing sound pulses between fixed transducers. The wind speeds up the pulses travelling with it and slows those travelling against it, and the difference gives speed and direction. With no cups, vanes or bearings there is no mechanical wear, although siting, icing and mast effects still matter.
A cup anemometer is a proven instrument, and a mechanical one. Its bearings wear, its starting threshold rises and its readings drift as it ages.
On an accessible site that is a maintenance schedule. On a mast, a tower, a buoy or a bridge, it is a climb, a vessel or a closure.
Ultrasonic measurement takes the rotating parts out. The sensor times sound between fixed transducers and calculates speed and direction from the difference.
Ultrasonic removes mechanical wear. It does not remove physics, which is why the rest of the installation still matters.
Ultrasonic does not remove physics
Replacing a cup and vane with an ultrasonic sensor changes one variable. Siting, icing, precipitation, mast effects and power still affect any anemometer, ultrasonic or mechanical, and each needs its own decision.
The benefit of ultrasonic is real, and it is specific: fewer visits, no wear-related drift and fast response.
Starting threshold
A mechanical sensor needs enough wind to overcome friction. An ultrasonic sensor has no friction to overcome.
WindSonic: starting threshold 0.01 m/s
One sensor, speed and direction
Cup and vane are two instruments. An ultrasonic sensor measures both in one head, with no direction dead band.
0 to 360 degrees, no dead band
Ice is still ice
Ultrasonic sensors are not immune to icing. Heated models exist because ice affects every anemometer.
Heated: WindSonic M, WindObserver, WindUltra
Turbulence needs a third axis
2-axis sensors measure horizontal wind. Vertical wind and turbulence need a 3-axis sensor.
3-axis: WindMaster and Research range
Cup and vane, or ultrasonic
Cup anemometers remain widely used and well understood. The table sets out where each approach tends to fit.
| Consideration | Cup anemometer and vane |  2-axis ultrasonic, WindSonic, WindObserver, WindUltra |  3-axis ultrasonic, WindMaster, Research range |
|---|---|---|---|
| Moving parts | Cups, vane and bearings | None | None |
| Measures | Horizontal speed and direction | Horizontal speed and direction | Three components of wind, including vertical |
| Wear over time | Bearing wear can change readings | No mechanical wear | No mechanical wear |
| Response | Limited by inertia | Fast, electronic | Fast; high output rates on the Research range |
| Best for | Established networks and standards built around cups | Operational wind measurement with fewer site visits | Turbulence, flux and research |
Ultrasonic is not always the better choice. Where a standard or an existing network is built around cup anemometers, continuity can matter more than the technology.
Location still matters
Flow distortion
The sensor head and its mount affect the airflow. Open-head designs such as WindObserver hold accuracy better as the flow angle increases.
Heating costs power
Heated ultrasonic sensors keep measuring in icing conditions, and the heater has to be in the power budget.
Wind range varies by model
WindSonic measures 0 to 60 m/s, WindSonic 75 and WindUltra to 75 m/s, WindObserver 90 to 90 m/s. Choose for the worst case at the site.
Siting still decides accuracy
No sensor can correct for a mast, a building or a tree upwind. Installation guidance applies to every anemometer.
Every Gill anemometer is ultrasonic
Every Gill anemometer is ultrasonic. The ranges differ by construction, wind range, heating, approvals and axes.
WindSonic
Cost-effective 2-axis ultrasonic anemometer
Gill’s most widely deployed wind sensor, for general measurement and OEM integration.
WindObserver
Heavy-duty open-head anemometer
Stainless steel 316, with the marine, aviation and hazardous-area approvals in the range.
WindUltra
Compact, lightweight and tough
The smallest and lightest Gill anemometer, heated, for mobile platforms and brutal sites.
WindMaster
3-axis ultrasonic anemometer
Three-dimensional wind for turbulence, site survey and airflow studies.
insight
Measure both ways, cancel the atmosphere
An ultrasonic anemometer sends a pulse of sound from one transducer to another, then back the other way. With the wind, the pulse arrives slightly sooner. Against it, slightly later.
Timing both directions lets the sensor calculate wind speed along that path from the difference. The speed of sound itself, which varies with temperature and humidity, drops out of the calculation.
Two or three paths at known angles give the wind vector: speed and direction in 2-axis sensors, and all three components in 3-axis sensors.
That is why an ultrasonic sensor does not need temperature correction for its wind output. It is also why the geometry of the head, and the mount beneath it, matter so much to accuracy.
The full explanation is in Ultrasonic anemometer vs cup anemometer
Wind without the climb
KnowledgeFull-range accuracy for Gill wind sensors
Accuracy published across the whole measurement range.
ApplicationCrane wind monitoring
Wind limits for lifting operations.
ApplicationAWOS and airport weather systems
Surface wind for aviation.
Application noteAN0036 Solar tracking farms
WindSonic protecting solar trackers.
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.
Ultrasonic wind questions
An ultrasonic anemometer measures the time sound pulses take to travel between pairs of transducers in both directions. Wind speeds the pulse one way and slows it the other, so the time difference gives the wind speed along each path. Combining paths gives wind speed and direction with no moving parts.
An ultrasonic anemometer is not always better, but it has specific advantages: no moving parts to wear, a very low starting threshold, fast response and speed and direction in one sensor. A cup anemometer remains a sound choice where a standard or an existing network is built around cups.
An ultrasonic anemometer has no rotating parts, so there is no bearing wear. It still needs inspection, cleaning where contamination builds up, and calibration checks appropriate to the application. It is not immune to icing, which is why heated models are available.
A 2-axis anemometer measures horizontal wind speed and direction. A 3-axis anemometer also measures the vertical component, which is needed for turbulence, flux and detailed airflow studies. Gill WindSonic, WindObserver and WindUltra are 2-axis; WindMaster and the Research range are 3-axis.
Heavy precipitation and icing can affect any anemometer, including ultrasonic sensors. Heated models such as WindSonic M, WindObserver and WindUltra are designed to keep measuring in icing conditions, at the cost of heater power.
WindObserver 90 measures wind speeds up to 90 m/s. WindSonic 75 and WindUltra measure up to 75 m/s, and WindSonic up to 60 m/s. The model should be chosen for the worst-case wind expected at the site.