The ultrasonic level meter is installed on the upper part of the container under the control of the electronic unit, and the probe emits a beam of ultrasonic pulse to the measured object. Sound waves are reflected off the surface of an object, and some of the reflected echoes are received by the probe and converted into electrical signals. The time from ultrasonic emission to being re received is proportional to the distance between the probe and the object being measured. The electronic unit detects the time and calculates the measured distance based on the known speed of sound. By subtracting, the level value can be obtained. Due to the influence of temperature on the speed of sound, instruments should measure temperature to correct the speed of sound.