A capacitance to digital conversion system wherein condition sensing capacitors are arranged with reference capacitors in a circuit configuration so as to eliminate the need for an absolute a. c. voltage thereby imparting a high degree of precision to the system. Primary error sources are virtually eliminated since all operations are performed on an error signal and a single oscillator drives both sensing and reference capacitors so that frequency variations in the output of the oscillator have no effect on the accuracy of the measurement being made. Additionally, the high degree of precision is accomplished with a significant reduction in hardware.
A capacitance to digital conversion system wherein condition sensing capacitors and reference capacitors are arranged with circuitry including a virtual ground and means for providing an error signal related to the sensed condition. The capacitors, virtual ground and error signal means are disposed within a sealed housing so that the system is isolated from environmental influences and is hence more stable than like systems known in the art.
System Having A Fixed Excitation And Providing A Variable Ratio Output
A system for providing a variable ratio output signal includes differential amplifier means for measuring the amplitude of a fixed reference signal relative to system ground. The measured signal is combined with a variable ratio command signal and a feedback signal to provide an output signal having a variable ratio amplitude relative to the fixed reference signal.