Patent ID: 6100682
Filing Date: 2000-08-08
Classification: G01B,G01D,G01P

Abstract:
A device for sensing angular positions of a rotating ferromagnetic target wheel having teeth, separated by slots, circumferentially spaced around the periphery of the target wheel, said device comprising:a magnetic sensor having a biasing magnet positioned adjacent the periphery of the target wheel;first, second and third sensing elements positioned adjacent the periphery of the target wheel and providing first, second and third signals each having an amplitude that changes in response to the passage of each leading and trailing edge of each tooth adjacent the respective elements;the first, second and third sensing elements being sequentially positioned with the second sensing element intermediate the first and third sensing elements and equally spaced so that they generate three sequential signals equally phase shifted by angles corresponding to their spacing;first differential circuitry responsive to the first sensing element signal and the second sensing element signal for providing a first differential signal;second differential circuitry responsive to the second sensing element signal and the third sensing element signal for providing a second differential signal;third differential circuitry responsive to the first differential signal and the second differential signal for providing a third differential signal responsive to crossover points between the first differential signal and the second differential signal; anddecoder circuitry coupled to the third differential signal for producing an output signal indicating the crossover points which correspond to the leading and trailing edges of each tooth of the target wheel.