Medical sensor with amplitude independent output

Claim 1

A pulse oximeter system comprising: (a) a sensor for attachment to a patient including a first light emitter for emitting light of a first wavelength, a second light emitter for emitting light of a second wavelength, a light to frequency converter integrated on a single semiconductor chip, said light to frequency converter including a photodetector and a current to frequency converter, and providing a frequency output signal, an automatic gain control circuit for separately adjusting the gain of said frequency output signal for said first and second wavelengths, a transmitter for transmitting said frequency output signal; and (b) a pulse oximeter monitor including a receiver input for receiving said transmitted frequency output signal, a bus connected directly to said receiver input to receive said frequency output signal as a digital signal without any analog to digital conversion, a microprocessor, coupled to said bus, for analyzing said frequency output signal as a digital signal to determine a corresponding amplitude value represented by said frequency output signal, said microprocessor being programmed to measure oxygen saturation.