Anemometers have to endure many harsh conditions. The device is located on the mast’s tip where it endures sunny days, rain, dust, and freezing weather. Moreover, the spinning components of the standard anemometer wear off eventually. In the SEVEN 3S-UA Ultrasonic Anemometer, we were willing to solve this issue once and for all.
The 3S-UA provides readings about the wind speed and wind direction simultaneously in one small case thanks to the ultrasonic technology. The device has no rotating components and therefore cannot wear off or freeze.
How Does the 3S-UA Measure Wind?
Ultrasonic pulses are sent from the transducers that work in opposite directions inside the device. The air flow makes the pulses move faster in one direction than in the other. This difference in travel time allows calculating both wind speed and direction within 1 second.
Measuring principle of the 3S-UA
Being totally electronic, the ultrasonic sensor detects light winds that may not be detected by a cup anemometer. In addition, it provides data on abrupt gusts and changes of wind direction. If you need more information on the comparison of these two types of anemometers, have a look at our article Cup Anemometer vs Ultrasonic Anemometer: What Is the Difference and Which Should You Choose?
Cup anemometer and wind vane compared with the 3S-UA ultrasonic anemometer
Key Technical Specifications
| Parameter | 3S-UA |
| Measured data | Wind speed and wind direction |
| Wind speed range | 0 … 75 m/s |
| Wind speed uncertainty | ±0.2 m/s or ±2% (0–35 m/s); ±3% (>35 m/s) |
| Wind direction range | 0 … 360° |
| Wind direction uncertainty | ±2° |
| Resolution | 0.1 m/s / 0.1° |
| Response time | 1 s |
| Output | RS485 (4800–38400 baud), Modbus RTU, SunSpec compatible |
| Power supply | 24–30 V DC (24 V DC recommended), typically 35 mA |
| Galvanic isolation | 1000 V between power supply and RS485 line |
| Operating temperature | -20°C … +60°C |
| Protection | IP66, UV-resistant ASA housing |
| Dimensions / weight | Ø156 × 258 mm / 480 g |
| Standard | WMO-No. 8 measurement compatibility |
Detailed information on this can be found in the 3S-UA product page and in the 3S-UA datasheet.
Reasons To Buy An Ultrasonic Anemometer
- Increased service life, reduced maintenance – there are no cups or bearings in the device.
- Ability to measure wind even at low speed: there is no starting limit, thus low-speed and even zero wind is measurable.
- Real time measuring: gusts and changes in wind direction are recorded right away – very important in case of decision making for stowing the solar tracker.
- Two-in-one device: speed and direction are measured with a single instrument connected with a single cable.
- Easy connection and control via RS485, ModBus RTU protocol, SunSpec compatibility, optional integrated termination resistor controlled directly from the GUI.
Applications of 3S-UA
Solar power plants, weather stations, wind farms, ports, airports, façade of buildings – everywhere where reliable and easy-to-maintain wind measurements are needed. It can be used alone or together with other sensors in SEVEN weather station.
Installation in Several Simple Steps
- Align the north pointer on the unit to true north.
Aligning the north marker of the 3S-UA with true north during installation
- Install the sensor into a location exposed to the elements where the wind is able to blow through.
- Separate AC/DC power lines from communication/power cables with at least a 35 mm bending radius.
- Turn on the termination resistor within the GUI if several units are connected to the same cable line.
- Ground the installation for protection against electrical noise.
References
- WMO-No. 8, Guide to Instruments and Methods of Observation, World Meteorological Organization.
- SEVEN Sensor Solutions, Ultrasonic Anemometer – 3S-UA. https://www.sevensensor.com/ultrasonic-anemometer
- SEVEN Sensor Solutions, 3S-UA Datasheet. https://www.sevensensor.com/files/d/en/3S-UA_Ultrasonic-Anemometer.pdf
- SEVEN Sensor Solutions, SEVEN Wind Sensors: Reliable Wind Monitoring for Smarter Solar Plant Performance. https://www.sevensensor.com/seven-wind-sensors-reliable-wind-monitoring-for-smarter-solar-plant-performance
Frequently Asked Questions (FAQ) about the 3S-UA
What does 3S-UA measure?
The wind speed range is 0 - 75 m/s, and the wind direction angle range is 0 - 360°.
Are there any moving parts in 3S-UA?
No. It measures wind speed by ultrasonic pulses; thus, there is no mechanical degradation.
What protocol does it work with?
Modbus RTU over RS485 at baud rates of 4800-38400 and it is SunSpec compliant.
What cable lengths are available?
Cable lengths of 3m, 5m and 10m are optional; other cable lengths are available upon request.
What is the warranty period?
Each 3S-UA unit comes with a warranty period of 2 years, free software updates and SEVEN remote setup assistance.
