For radar level meters, the reliable detection and indication of an empty tank is quite a challenging task. Especially in tanks with conical or dished bottom, we find the situation that when the tank is empty the radar wave hits the bottom at an angle and is not reflected in the direction of the antenna.
Explained in a simple way, the radar signal behaviour can be compared to a mirror reflecting an image. If the mirror is not perpendicular to an object the observer cannot see it. A tank is like multiple mirrors where the radar wave, after many reflections, finally hits the sensor again. However, the travelling time of the radar wave has increased which causes false readings.
The level meter will search for any signal for as long as necessary until it will find a “valid” reflection. This could be a welding seam on the tank wall, a small peak of an agitator blade or anything else which we can find inside a tank. The result will be the indication of a wrong level, which can lead to a massive disturbance of the process.
In the past, this situation could be handled manually by adjusting some advanced setting parameters. Based on many years of experience and know-how in radar level measurement, KROHNE has developed special algorithms and integrated them into the OPTIWAVE series as Tank Bottom Management (TBM). TBM detects false reflections and adjusts all parameters automatically. Thus, it allows for quick and easy commissioning of tanks regardless of their size, material or geometry.
In an empty tank, the radar wave hits the bottom at an angle and is not reflected in the direction of the antenna. TBM (Tank Bottom Management) compensates for this effect and ensures reliable measurement.