Even though the general concept of ultrasonic and mechanical wind speed measurement sensors is the same, their operation is unique because of their different designs. Because of this, it is important to understand the pros and cons of both types of anemometers.
Ultrasonic Wind Speed Measurement Sensors
For starters, ultrasonic anemometers need less maintenance and are proven to respond far better to rapid wind gusts. A primary difference is that ultrasonic sensors have no moving parts; instead, a pulse of ultrasonic sound is sent by a transducer from the north-facing side while the time required to travel to the south transducer is measured by a microprocessor. The speed of wind is calculated from the time it takes the pulse to travel from one transducer to the other.
Things like wind speed and direction that blows along a line between the two affects measurement time. Because ultrasonic wind speed measurement sensors have no moving parts, the measurements are immediate and extremely precise.
Mechanical Wind Speed Measurement Sensors
In comparison, mechanical sensors have moving parts: cups that detect wind speed and a vane for vectoral change. Anytime there is a change in the wind, these parts physically move, ensuring both speed and directional readings are accurate.
Although the accuracy of measurements over time is much the same for both, things like gusts and turbulence are not always detected by mechanical sensors simply because the moving parts have limitations.
In measured wind speed, observed differences occur due to the amount of time required for a mechanical sensor to start up physically or register a change in wind direction. For instance, when a storm with quick directional changes blows through, a sensor in a mechanical anemometer has to slow down, stop, and then restart with the wind direction change. For the change to be registered and reported, several seconds pass.
However, with ultrasonic wind speed measurement sensors, the change in wind direction is measured immediately. Therefore, the National Weather Service updated its 883 Automated Surface Observation Systems, choosing ultrasonic sensors as opposed to mechanical ones. This spurred upgrades and a new requirement by the Federal Aviation Administration whereby all sensors must be able to measure variable gusts of wind at 3-second intervals.