Ultrasonic level gauges are digital level gauges controlled by a microprocessor. In the measurement, the ultrasonic pulse is emitted by the sensor (transducer), the sound wave is reflected by the liquid surface and received by the same sensor, converted into an electrical signal by a piezoelectric crystal, and the distance from the sensor to the surface of the measured liquid is calculated by the time between the emission and reception of the sound wave. Due to the non-contact measurement, the measured medium is almost unlimited, and can be used for a wide range of liquid and solid material height measurements.