Short ultrasonic impulses in the range of 35 to 70 kHz are emitted by the transducer to the measured product, reflected by the product surface and received again by the transducer. The pulses are spread with sound velocity. The time from emission to reception of the signals is proportional to the level in the vessel. The proven ECHOFOX signal processing analysis the reflections in the vessel based on long-standing experience and detects the level signal reliably. The adjustment of the sensors is very simple without changing the level.