Electricity: measuring and testing – Magnetic – Displacement
Patent
1997-03-10
2000-01-11
Snow, Walter E.
Electricity: measuring and testing
Magnetic
Displacement
32420716, 32420726, G01B 714
Patent
active
060140224
ABSTRACT:
A proximity sensing circuit is provided with various attributes, including the connection of a proximity sensor coil in a feedback loop of an amplifier, the frequency hopping technique that periodically changes the two frequencies used by its proximity sensor circuit to avoid deleterious interference by constant frequency EMI sources and the provision of a self diagnosis technique, The connection of the proximity sensor coil in the feedback loop of an amplifier results in several advantages including the connection of the coil to a virtually infinite impedance, the reduction of the number of components needed in the proximity sensing circuit and decreased temperature sensitivity of the overall circuit. The frequency hopping technique that periodically changes the two frequencies used by the proximity sensor significantly decreases the likelihood that a constant frequency EMI source in the vicinity of the circuit will have a continually adverse affect on its accuracy and reliability. In applications that require a large number of sensors, the circuit uses a multiplexer with a plurality of sensors and a single filtering network to decrease the necessary number of components in the proximity sensing circuit. Self diagnosis can be performed by using precision resistors or by intelligently monitoring the changing values of the AC impedance, the DC resistance and the compensated resistance, either individually or in combination with each other, to predict certain potential malfunctions.
REFERENCES:
patent: 4652821 (1987-03-01), Kreft
patent: 5099845 (1992-03-01), Besz et al.
patent: 5243337 (1993-09-01), Beauducel et al.
Demma Nick A.
Lenz James E.
Milosevic Dragutin
Simonelic Joseph J.
Fredrick Kris T.
Honeywell Inc.
Snow Walter E.
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