Importance

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Abstract

A lamp monitor provides a sense resistor for each lamp circuit as a special sense terminal member with a series resistance and sense terminals connected to a circuit board in a lamp monitor module. A multiplexing arrangement allows selection of the circuit to be monitored. The monitor samples the voltage across the series resistance by first connecting a capacitor across the sense terminals to be charged to the voltage and then disconnecting the capacitor from the sense terminals and connecting it across the input of an amplifier. The voltage across the lamps is sensed to provide a ratiometric reference for the digitizing of the amplifier output in an analog to digital converter; and a digital computer corrects the input digital signal with a stored non-linear normalization factor relating current to voltage in the lamps. The normalized value is compared with a predetermined percentage of a learned reference to determine lamp outage; and the learned reference is updated at a slowed rate when no lamp outage is detected.

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First Claim