In a tachogenerator for detecting the rotation speed of a rotating machine part, in particular that of a vehicle wheel, having a predetermined measurement resolution, having at least one magnetically acting encoder which can rotate with the machine part, has magnetically acting areas which are subdivided in a predetermined sequence into angle parts, in particular teeth composed of ferromagnetic material or a magnetic pole ring, and which, during rotation, produces a measurement signal in at least one magnet sensor which is arranged to be stationary relative to the encoder and is separated from said encoder by an air gap, which measurement signal corresponds to the angular pitch of the encoder and whose frequency corresponds to the rotation frequency of the machine part, in order to produce measurement signals which can be evaluated with an air gap which is not constant, the angular pitch of the encoder is coarser than the predetermined measurement resolution requires, and at least two magnet sensors are provided, which are arranged fixed one behind the other in the rotation direction, relative to the encoder, in order to produce at least two mutually phase-shifted measurement signals which correspond to the angular pitch of the encoder, and means are provided for linking the measurement signals emitted by the sensors to form an output signal, with the output signal being at a frequency which is greater than the measurement signals of the magnet sensors, in order to achieve the predetermined measurement resolution.
Apparatus and methods for detecting passing magnetic articles using a first, True Power On State (TPOS) detector during a first time interval and transitioning to a second, running mode detector after the first time interval, when the output of the second detector is accurate. A phase comparator is responsive to the output signal of the first and second detectors and provides a control signal indicative of a change in the phase relationship between the two output signals. An output switch controlled by the phase comparator provides, as the detector output signal, the first detector output signal during the first time interval and the second detector output signal thereafter. A threshold signal associated with the TPOS detector is at a fixed level during a first portion of the first time interval and is adjusted during a second portion of the first time interval in response to an automatic gain control circuit in order to reduce the phase error associated with transitioning from the TPOS detector to the running mode detector. Also described are apparatus and methods for updating a running mode threshold signal that is a percentage of the peak-to-peak magnetic field sensor signal, so that unnecessary update events are reduced.
A speed measuring system comprising at least one stationary speed sensor (4) for detecting a speed of a measuring body (1) rotating relative to the speed sensor (4) wherein the measuring body (1) is provided, on its periphery, with electric or magnetic discontinuities. The speed sensor (4) situated at a defined distance from the measuring body (1), reacts to the discontinuities when the measuring body (1) is moved past the speed sensor (4). The speed measuring system has, in addition, one separate distance sensor (5) for determining an actual distance (LS) and an actual change in distance between the speed sensor (4) and the measuring body (1). In an evaluation device of the speed measuring system the speed of the measuring body (1) is formed from an actual output signal of the speed sensor (4) according to an actual output signal of the distance sensor (5).
A device for measuring the angle of rotation of a rotating member of a machine, comprising a signal transmitting rotor which includes a magnet rim consisting of magnets having alternatingly arranged south poles and north poles and being moved with respect to a stationary measuring sensor is characterized in that each magnet or each magnet zone has a thickness which varies substantially sinusoidally in circumferential direction, having its maximum in the pole center of each magnet and/or forms an air gap with the measuring sensor varying sinusoidally in circumferential direction.
Apparatus and methods for detecting passing magnetic articles using a first, True Power On State (TPOS) detector during a first time interval and transitioning to a second, running mode detector after the first time interval, when the output of the second detector is accurate. A phase comparator is responsive to the output signal of the first and second detectors and provides a control signal indicative of a change in the phase relationship between the two output signals. An output switch controlled by the phase comparator provides, as the detector output signal, the first detector output signal during the first time interval and the second detector output signal thereafter. A threshold signal associated with the TPOS detector is at a fixed level during a first portion of the first time interval and is adjusted during a second portion of the first time interval in response to an automatic gain control circuit in order to reduce the phase error associated with transitioning from the TPOS detector to the running mode detector. Also described are apparatus and methods for updating a running mode threshold signal that is a percentage of the peak-to-peak magnetic field sensor signal, so that unnecessary update events are reduced.
