Displacement measuring device e.g. revolution monitor based on fluctuating magnetic field

摘要

A movement or revolution monitor (10), for example for noting turning speed, comprises a cog wheel (1) coaxial with the object to be monitored made of magnetic material and with rectangular teeth (21,22) spaced at a gap of. This is positioned opposite the north pole of a magnet (3) wider than the cog-spacing. During turning of the wheel a cyclical magnetic field is formed in the space between wheel and magnet, in which coupled zig-zag magneto resistive elements (41,42) are positioned so that their longer sections are at an angle of 45/135 degrees to the line of magnetic force. These have connections (5,6,7) to a monitor which notes their changes in resistance in direct relationship to the altered magnetic angle as each tooth on the cog wheel passes. The system is small and inexpensive but also accurate and durable.