To measure the level of a tank, these sensors use ultrasonic technology. During operation, the ultrasonic transducer emits acoustic pulses in a narrow beam perpendicular to the transducer face. The time between the emission of the pulse and the reception of the echo is calculated and this is used to determine the distance to the material. The integral temperature sensor automatically compensates variations in sound velocity due to temperature changes within the permissible range. Because the instrument is not ever in contact with the medium, this instrument can be used on very aggressive or corrosive media and will have a very long service life.