Ultrasonic level meter installed in the upper part of the container, under the control of the electronic unit, the probe to the measured object to launch a beam of ultrasonic pulse. The acoustic wave is reflected by the surface of the object, and the partially reflected echo is received by the probe and converted to an electrical signal.
From the ultrasonic launch to be re-received, the time and the probe to the measured object is proportional to the distance. The electronic unit detects the time and calculates the measured distance based on the known sound velocity. The level value can be derived by subtraction.