Patent ID: 7409866

Claim:
Apparatus for transmitting a transducer signal to be measured from a signal generation location to a measuring location connected by a single wire where said transducer signal is subjected to undesired variations caused by multiple sources, comprising: a transducer positioned at said signal generation location and operative when biased by a power source to provide an output signal according to a monitored condition, a reference level generator coupled to said power source and operative to provide a reference level output proportional to the value of said power source, a multiplexer for receiving at one multiplex input said transducer output signal and at another input said reference level output to provide at a multiplexer output said transducer signal for a first interval and said reference level for a second interval, a converter responsive to said multiplexer output for said transducer signal for converting said transducer signal to a first frequency modulated signal having a frequency output variation according to the value of said transducer output signal during said first interval and for providing a second frequency modulated signal indicative of said reference level during said second interval, wherein variations in signals which may be caused by multiple sources are present in both signals, and a measuring circuit positioned at said measuring location and responsive to said modulated signals to provide the ratio of the periods of said signals wherein said ratio is a direct measure of said transducer output signal with said variations substantially eliminated.