US 4,028,686 AGranted

Digital detector

AssigneeElectro Corporation

InventorsMichael A. Wilson, Gordon E. Gee

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Abstract

A detector for a dynamic phenomenon with a cyclically varying condition, as motion of a rotating part. At least three digital sensors are separated in phase with respect to the cyclic condition. The instantaneous outputs of the sensors have a plurality of repeating sequential states so long as the dynamic phenomenon exists. The instantaneous outputs of the sensors have at least one state which does not occur during existence of the dynamic phenomenon but which does occur in the absence thereof. Logic circuits respond to the digital sensor outputs and detect information about the dynamic phenomenon. Detection of the repetition rate of an instantaneous output state of the sensors provides a measure of speed. An absence of rotation is indicated by the occurrence of another output state. In another disclosed embodiment, the detector monitors a three phase power system and detects a phase outage by the occurrence of an abnormal sensor output state.

Claims3

Dependent claims

In a speed detector for a rotary member having:

an element with an annular array of alternate slots and teeth of magnetic material,
an odd plurality of magnetic sensor means operably associated with said array of slots and teeth and responsive to relative motion between the array and sensor means,
circuit means to develop alternate digital 1 and 0 outputs from each sensor means, each sensor means being displaced from the other sensor means with respect to the slots and teeth whereby during relative motion the instantaneous outputs of the circuit means have a plurality of sequential states and there is at least one state of the circuit means outputs which does not occur during relative motion but does occur in the absence of such motion,
an AND gate having inputs connected with said circuit means and responsive to one of said plurality of sequential output states to generate a repetitive motion-indicating signal, and
an output circuit actuated by the motion-indicating signal from said AND gate to provide a measure of speed,
an improved inhibiting means for said output circuit, comprising:
an AND gate having inputs connected with the outputs of said circuit means and responsive to said one state of circuit means outputs which does not occur during the motion of the array to generate a fault signal;
means responsive to said fault signal for inhibiting operation of said output circuit;
and
means responsive to repetitive occurrence of one of said plurality of sequential states subsequent to the generation of a fault signal, to enable said output means.

7 more elements

Dependencies are inferred from the claim text.