An Ultrasonic pulse is transmitted via a coupling media through the wall of a tank into the liquid, reflected at the liquid's surface and travels back to the sensor. If the time of flight is shorter than that chosen for the level limit, the sensor will switch. When the sensor is installed on the side of a tank or on pipes the time of flight is measured via being reflected from the opposite wall, whereby the travelling time is much longer in gaseous phase than in liquid. If this time so is outside a given window the sensor switches to the dry state.

A big advantage of this measuring principle is that there is no influence by the gas atmosphere. Especially the thermal coefficient for ultrasonic velocity of liquids is much smaller than those of gases, which results in less influence on the measuring results compared to those principles measuring from top through the gaseous atmosphere. Heavy crustings and sediments on the bottom also reduce the signal quality by damping and straying effects which may also occur with highly viscous dispersed or bubbling media.

Level limit and residual liquid detection on any containment or pipe by measuring through the wall.

The wall's material may be metallic, plastics, GFK, glass and also combination with coatings free of gas inclusions like Emaille, which thickness may be between 0,5 and 50 mm. Any gas content like in foam or with linings should be avoided, as these cause stray dispersion for the ultrasonic pulse and so reduce the signal quality. The thicker the wall is the bigger the minimum measurable liquid level will be. Double walled tanks are excluded from application.

The sensor will be installed into a fixing part which may be clamped, cemented or welded onto the wall. For installation you will have a big advantage because you do not need openings in the containment and therefore retrofitting can be performed during operation. Additionally there is no need of taking into account corrosive aspects which results in safe operation in aseptic application or with highly aggressive media. There is no problem  with leakage any more!