Speed sensor and conditioning circuit
First Claim
1. Speed sensor and conditioning circuit for measuring the rotational speed of a rotating member, comprising a sensing head including an inductive coil, said conditioning circuit including a comparator having an active input receiving the pulses generated by the sensing head, said comparator comparing the pulses generated by the sensing head with a reference signal and generating an output signal transmitted to a digital input port of a microprocessor, said conditioning circuit further including test circuit means for receiving a test signal from said microprocessor and causing said comparator to generate an output pulse of a predetermined duration if the speed sensing head is operative, said output pulse being transmitted to said digital input port.
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Accused Products
Abstract
A speed signal conditioning and test circuit includes a comparator which is connected to a digital input port of a microprocessor and which switches its output in response to the alternating current generated by the sensor when sensing wheel speed. A test sequence is initiated by injecting a signal into a tuned circuit formed by the inductance of the sensor coil, the filtering capacitors, and associated circuit resistances. The voltage output of the tuned circuit increases exponentially and switches the comparator to provide a test pulse of a predetermined time period. The microprocessor times the pulse to establish that an operative sensor is present. Since the inductance of the coil is switched out of the circuit in the case of an open or shorted sensor coil, no pulse is generated and the microprocessor accordingly determines that a defective sensor is present.
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Citations
18 Claims
- 1. Speed sensor and conditioning circuit for measuring the rotational speed of a rotating member, comprising a sensing head including an inductive coil, said conditioning circuit including a comparator having an active input receiving the pulses generated by the sensing head, said comparator comparing the pulses generated by the sensing head with a reference signal and generating an output signal transmitted to a digital input port of a microprocessor, said conditioning circuit further including test circuit means for receiving a test signal from said microprocessor and causing said comparator to generate an output pulse of a predetermined duration if the speed sensing head is operative, said output pulse being transmitted to said digital input port.
- 11. Method of testing a speed sensor and conditioning circuit for measuring the rotational speed of a rotating member and for transmitting a signal representing said rotational speed to a digital input port of a microprocessor, said speed sensor including a sensing head including an inductive coil, said conditioning circuit including a comparator having an active input receiving the pulses generated by the sensing head, said method including the steps of causing said microprocessor to generate a test signal, transmitting said test signal to said conditioning circuit, exciting a tuned electronic circuit including said inductive coil with said test signal for causing said tuned electronic circuit to generate a time varying signal if the sensing head is operative, transmitting said time varying circuit to said comparator, causing said comparator to generate an output pulse of a predetermined duration if the time varying signal is generated, and transmitting said output pulse to said digital input port of the microprocessor.
- 15. Speed sensor and conditioning circuit for measuring the rotational speed of a rotating member, comprising a sensing head including an inductive coil, and a serrated tone wheel having circumferentially spaced serrations, said tone wheel being mounted for rotation with said rotating member, said sensing head being mounted adjacent said tone wheel and being responsive to rotation of the serrations past said sensing head to generate a pulsed output signal, said conditioning circuit including a comparator having an active input receiving the pulses generated by the sensing head, said comparator comparing the pulses generated by the sensing head with a reference signal and generating an output signal transmitted to a digital input port of a microprocessor, said conditioning circuit further including test circuit means for receiving a test signal from said microprocessor and causing said comparator to generate an output pulse of a predetermined duration if the speed sensing head is operative, said output pulse being received at said digital input port.
Specification