Ultrasonic sensors work by sending sound waves that echo off of a target and return to the transmitter. The term ultrasonic means above human hearing, or any sound wave above 20 kHz. This method is quite accurate, and the sensors have an accuracy of 0.25% of detected range.
Because the speed of sound is a constant, under fixed atmospheric conditions, the time from the sound burst to the return is measured and translated into a distance. The sensor’s microprocessor calculates the distance and converts it to a level indication, volume measurement, or a rate of flow. It also compensates for temperature, and filters the signal.
Common uses for ultrasonic level sensors are level, volume, and flow monitoring. Other uses include presence or absence detection, and object dimensioning.