Patent ID: 7023205

Claim:
An eddy current sensor for measuring characteristics of a nearby, moving, electrically conductive object with an intervening barrier of material between the sensors and the object, the sensor comprising: a uniaxial permanent magnet for generating a stationary magnetic field, the magnet being mounted proximate and external to the barrier and sized and shaped so that the stationary magnetic field penetrates through the barrier and can be intersected by the moving conductive object; and a coil wound around the magnet so that a signal voltage can be produced on the coil in response to a variable magnetic field caused by eddy currents in the conductive object as the conductive object passes through the stationary magnetic field; wherein the magnet includes a first dimension along a longitudinal central major axis generally parallel to the proximate surface of the barrier, a second dimension along a second minor axis, and third dimension along a third minor axis, the first dimension being the greatest, and wherein the magnet is magnetized along one of the second minor axis and the third minor axis, whereby the sensor is monodirectional.