Communications: electrical – Selective – Having indication or alarm
Patent
1979-12-26
1982-02-16
Waring, Alvin H.
Communications: electrical
Selective
Having indication or alarm
340 59, 340620, G08B 2100
Patent
active
043161740
ABSTRACT:
A capacitive probe for sensing the presence of water in a fuel tank increases in capacitance when water is present. A threshold detector circuit includes the capacitive probe and a reference capacitor and an oscillator for periodically charging them to the same voltage and a comparator for comparing the capacitor voltages during discharge to determine when the probe capacitance exceeds the reference capacitance. The comparator controls a lamp driver which is connected to ground and which is also connected by a single conductor to a remote indicating lamp in series with a power supply. The single conductor carries the lamp energizing current as controlled by the lamp driver and also supplies the operating voltage to the detection circuit. The resistance of the incandescent lamp varies with applied voltage so that the voltage presented to the detector circuit is partially regulated by the lamp resistance so that large changes in the power supply voltage are only partially reflected in the threshold circuit operating voltage.
REFERENCES:
patent: 3694804 (1972-09-01), Hill
patent: 3939470 (1976-02-01), Arai et al.
patent: 4001676 (1977-01-01), Hile et al.
patent: 4107658 (1978-08-01), Hill et al.
Creager John E.
Gelenius Robert B.
Sutton Stephen J.
General Motors Corporation
Hill Warren D.
Waring Alvin H.
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