LIQUID-LEVEL SENSOR WITH ELASTIC-WAVE ABS ORPTION

This new type of liquid level sensor is based on the attenuation of el astic waves guided in a hollow cylinder partially immersed in the liqu id. The cylinder (10 cm long) is suspended at one end of a few meter l ong magnetostrictive wire. The acoustic waves are launched in the wire by a pulse of current in a coil and after propagating are transmitted through a cylindrical horn to the hollow cylinder. The carrier freque ncy of the wave trains and the thickness of the tube are chosen so tha t the waves strongly leak into the liquid when the cylinder is immerse d. Then, this sensor is automatically maintained just immersed by wind ing or unwinding the wire so that the waves can leak. The level is fin ally determined by measuring the time-of-flight of the echo reflected at the junction between the wire and the horn.