Electricity: measuring and testing – Electric lamp or discharge device – Electric lamp
Patent
1989-09-22
1992-03-10
Wieder, Kenneth A.
Electricity: measuring and testing
Electric lamp or discharge device
Electric lamp
324503, 324522, 324537, 324550, 340641, G01R 3122
Patent
active
050952749
ABSTRACT:
An apparatus for monitoring current through a lamp circuit that uses a series resistance shunt in the circuit with one end being connected to a current source and the second end being connected to the lamp. The circuitry includes a comparator that is connected across the shunt and has a threshold switching voltage such that a voltage across the shunt that is larger than the threshold voltage will switch the comparator on (as in the case where the lamp is not functioning) and a voltage across the shunt that is smaller than the threshold voltage (as in the case where the lamp is in the circuit and functioning) will switch the comparator off. In a preferred embodiment, the shunt is actually a portion of the printed circuit board trace. In order to compensate for changes in resistance in the shunt that occur as the temperature of the printed circuit board trace changes, temperature compensation circuitry is included to maintain the threshold switching voltage in a fixed relationship with the temperature of the shunt. The apparatus incorporates additional circuitry connected to the comparator in order to decrease the sensitivity of the comparator to changes in the circuit supply voltage. In a preferred embodiment, the circuit has a 50% sensitivity to supply voltage changes. The circuit may be manufactured in monolithic integrated circuit form in order to enhance reliability, cost, and manufacturability.
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patent: 4884033 (1989-11-01), McConchie, Sr.
Analog Devices Inc.
Mueller Robert W.
Wieder Kenneth A.
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