Patent ID: 7570041

Claim:
A magnetic field position sensing device for sensing the position, on a front surface of a barrier of a magnet of known magnetic field intensity secured to a rear surface of said barrier; said magnet having attachment means to retain same on said rear surface, said sensing device having a housing in which is mounted a linear magnetic field transducer which generates output voltage signals to a microcontroller proportional to a detected magnetic field intensity of said magnet, said microcontroller having a reference signal value stored in a memory thereof and calibrated to a maximum signal strength of said magnet when positioned directly adjacent said transducer without obstruction, a digital display device connected to said microcontroller for displaying a visual digital value of said detected magnetic field intensity which is indicative of the thickness of said barrier, audible/visual means for transmitting an audible signal representative of measured values of said field intensity as said transducer is displaced on said front wall surface by moving said housing in a diminishing spiral path to locate a center position of said magnet where said magnetic field intensity is the greatest and modifying said visual digital value display accordingly whereby to locate the position of said magnet relative to said front surface of said barrier and determining the thickness of said barrier.