Patent ID: 7024932

Claim:
Device for detecting the level of a material which is liquid or powdery or even solid in separated form ( 2 ; 22 ), and which is, or is made, electrically conductive and with which a container ( 4 ; 24 ) having a vertical axis is filled or of which said container is emptied, or the position of a monolithic and electrically conductive solid material which is mobile in the container, this device being characterised in that it comprises: an inductor ( 8 ; 32 ) which is provided to create an alternating electric current in the material and which surrounds the container and has the same axis as this container, the latter being approximately transparent to the magnetic field generated by the inductor, an alternating current source ( 10 ; 34 ) provided to supply the inductor with current, at least one magnetic field sensor ( 13 ; 52 , 54 ) which is placed between the inductor and the container axis and orientated along an approximately horizontal axis meeting the container axis, so as to detect the partial differential, along the inductor axis, of the radial component of the magnetic field, the magnetic field sensor comprising a pair of transductors ( 11 – 12 , 56 – 58 , 60 – 62 ), mounted in a differential way and placed one over the other, the sensitive axes of the transductors being approximately parallel, the axis along which the magnetic field sensor is orientated being in the plane defined by these two sensitive axes and being equidistant from them, means ( 16 ; 68 , 70 ) for demodulating the signals supplied by the magnetic field sensor, demodulation occurring with a phase shift of approximately π/2 relative to the current supplied by the source, and processing and signalling means ( 18 , 20 ; 72 , 74 , 76 ) provided to process the signals provided by the demodulation means and to provide a signal indicating that the level of the magnetic field sensor has been reached by the material.