Recent updates to FT Technologies 722 and 742 digital wind sensors mean that these models can now read acoustic temperature as well as wind speed and wind direction. The air temperature is derived from the operating frequency of the sensor and has an accuracy of ±1°C. This version of the software is available by special order at no extra cost.
With this upgrade, customers who already use FT digital wind sensors for wind speed and direction measurement, will now be able to read the air temperature as well from one maintenance-free device. The FT742-SM model also includes an electronic compass.
FT wind sensors work by establishing a resonant, ultrasonic frequency in the measurement cavity and then measure the phase change of that ultrasonic signal as air passes through the cavity. The resonant frequency varies with the speed of sound which itself is heavily dependent on air temperature and, to a lesser extent, relative humidity and air pressure. Therefore the sensor can derive the temperature of the air from the frequency of the ultrasonic signal – hence this feature is named ‘acoustic temperature’.
In common with all ultrasonic systems measuring acoustic temperature, the accuracy is affected by the temperature difference between the sensor itself and the air temperature in the cavity. With the heater off, accuracy is ±1°C at wind speeds between 5m/s and 60m/s and at temperatures ranging from -20°C - +60°C. With the heater on, accuracy is ±2°C.
With no moving parts to break or degrade, FT sensors are ideal for use in extreme conditions and where sensors are required to operate for long periods of time without any maintenance.