Hamilton Standard Controls, Inc.

Terumi Tsugawa

A sensor is connectable with a load circuit via two conductors. The sensor receives its electrical power from the load circuit via the two conductors and similarly provides its output signal indicative of the sensed phenomenon via the same conductors. An unregulated source potential is provided to a terminal of the sensor from a supply potential via the load circuit. Voltage regulating circuitry in the sensor converts the unregulated source potential to a regulated operating potential for its active circuit elements. Certain output circuitry in the sensor is connected to the terminal having the unregulated source potential for conveying an output signal from the sensor to the load circuit.

Sensor having two-wire connection to load

A speed detector, for use with a tone wheel having metal teeth, employs two coils positioned in offset relation near the tone wheel for interacting with the tone wheel teeth and thus changing their respective inductances. One coil is in a phase sense oscillator circuit and the other is in a tuned sensor network. The oscillator is coupled to, and drives, the tuned network. The change in coil inductances effects a shifting of the phase of the output signal from the oscillator relative to the output signal from the tuned network. The phase sequence of those two output signals also reverses itself cyclically as the tone wheel rotates, and a phase reversal detector detects that reversal and uses the event to provide timing reference pulses for a final determination of speed. The speed detector has a hysteresis circuit connected between the phase reversal detector and the oscillator or the tuned network for automatically increasing the apparent phase shift between the oscillator and tuned circuit output signals to minimize invalid timing signals as a result of limited backward motion of the tone wheel. The hysteresis circuit includes a resistor and preferably a series diode.

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Fountain Valley, CA, United States of America

Terumi Tsugawa