Circuit configuration having a pair of multi-Hall generator Hall sensors and high pass filter for contactless detection of the rpm of a rotating gear wheel

• US 5,084,674 A
• Filed: 10/12/1989
• Issued: 01/28/1992
• Est. Priority Date: 10/13/1988
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Lachmann, Ulrich, Jasberg, Hartmut
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US07/420,338
• Time in Patent Office: 838 Days
• Field of Search: 338/32 H, 307/309, 328/167, 73/518, 73/519, 324/160, 324/463, 324/166, 324/173, 324/174, 324/207.20, 324/207.21, 324/207.25, 324/225, 324/251
• US Class Current: 324/174
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors

Abstract

A circuit configuration for contactless detection of the rpm of a rotating gear wheel includes two identical firmly mounted and magnetically prestressed Hall sensors being mutually spaced apart by a center distance equal to one-half the tooth pitch of a gear wheel whose rpm is to be detected. Each of the Hall sensors includes at least one pair of identical Hall generators having signal paths and being driven with an impressed control current or impressed control voltage. Voltage/current converters are each coupled to the signal path of a respective one of the Hall generators and each have an output. An evaluation circuit links together the outputs of the voltage/current converters connected to one of the Hall sensors and the outputs of the voltage/current converters connected to the other of the Hall sensors in phase opposition.

Claims

1. Circuit configuration for contactless detection of the rpm of a rotating gear wheel, comprising two identical firmly mounted and magnetically prestressed Hall sensors, wherein the teeth of the gear wheel of which the rpm is to be detected, are mutually spaced apart by a center distance equal to twice the center distance between the Hall sensors, each of said Hall sensors including at least one pair of identical Hall generators having a driving signal input and a signal output, said driving signal input being driven with an impressed control current or impressed control voltage, voltage/current converters each with inputs and outputs, each input being coupled to a signal output of a respective one of said Hall generators, and an evaluation circuit including a high-pass filter with an input and an output, and a comparator with switching hysteresis having an input and an output, wherein the outputs of said voltage/current converters, whose inputs are connected to one of said Hall sensors and the outputs of said voltage-current converters, whose inputs are connected to the other one of said Hall sensors are linked together in phase opposition, and are connected to the input of said high-pass filter, the output of said high-pass filter being connected to said input of said comparator, wherein said high-pass filter includes an operational amplifier having an inverting input, a non-inverting input and an output, a reference voltage source connecting the inverting input to zero potential, two controllable current sources, the first of said controllable current sources being connected between a supply potential and the non-inverting input of said operational amplifier, the second of said controllable current sources being connected between zero potential and said non-inverting input of said operational amplifier, the first of said current sources being controlled by an output signal of said voltage/current converters, the second of said current sources being controlled by a signal present at the output of said operational amplifier, a capacitor connected between the non-inverting input of said operational amplifier and the zero potential, and the difference between the signal at the output of said operational amplifier and the output signal of said voltage/current converters forming an output signal of said high-pass filter.

2. Circuit according to claim 1, wherein said Hall generators of each of said Hall sensors are rotated through 90°

relative to each another.

3. Circuit according to claim 1, wherein said voltage/current converters are differential amplifiers with output branches carrying signal currents of opposed phase relation, each input of said differential amplifier being connected to the signal output of said Hall generators, and the output branches of said differential amplifiers of one of said Hall sensors carrying signal currents of the same phase relation and the output branches of said differential amplifiers of the other of said Hall sensors carrying signal currents of opposed phase relation being joined together and connected to said evaluation circuit.

4. Circuit according to claim 1, including a trigger circuit with an output of said output of said trigger circuit being connected to said driving signal inputs of said Hall generators, said Hall sensors, said evaluation circuit and said trigger circuit being joined together into an integrated circuit.