Patent ID: 8384377

Claim:
A tachometer for supplying a signal representative of rotational rate and absolute position of a rotatable device, comprising: a plurality of detection magnets coupled to, and spaced around, the device, to thereby rotate with the device when the device is rotated; an index feature associated with the rotatable device, to thereby rotate with the device when the device is rotated, wherein the index feature and the plurality of detection magnets are spaced evenly around the device; a plurality of non-rotationally mounted magnetic circuits spaced evenly around the device, each magnetic circuit configured to supply a first electrical signal each time one of the detection magnets rotates past the magnetic circuit and a second electrical signal each time the index feature rotates past the magnetic circuit; an energy harvester coupled to receive the first and second signals supplied by each of the magnetic circuits and configured, upon receipt thereof, to supply regulated electrical power; and a signal conditioner coupled receive to the regulated electrical power and the first and second signals supplied by each of the magnetic circuits and configured, in response thereto, to supply a rate signal representatives of device rotational rate.