The measuring principle
The distance measurement is based on the principle of pulse echo method, ie one at a certain time t0 transmitted ultrasonic pulse hits for a dependent of the speed of sound at the time t1 on the measured object is reflected and reaches the time 2 * t1 back to the ultrasonic sensor.
The elapsed time (run time) depends on the distance of the object and the ambient temperature T. The effect of temperature compensated by using an auxiliary reflector. The distance between the reflector and the temperature sensor is known and is hereby made the temperature compensation. Only by this compensation, it is possible to achieve accuracies of 100 microns at the UAS systems.