Elsag International N.v.

Brian D Hemphill

Joseph C Nemer

A signal isolating device for an input digital signal has a first photo-coupler which is activated by the differential pulse produced at the leading edge of the digital signal and a second photo-coupler which is activated by the differential pulse produced at the trailing edge of the digital signal. A positive feedback system is connected in push-pull fashion with the photo-couplers for producing an output digital signal that corresponds to the input digital signal. The positive feedback system may be implemented by a buffer that includes a resistor for keeping the buffer in a stable state even when both of the photo-couplers are non-conductive.

Low power digital signal isolator

A method and apparatus for calculating a ratio, R, having a first capacitance value, C.sub.1, in inverse relation to a second capacitance value, C.sub.2, where C.sub.1 and C.sub.2 are the capacitance values of a first capacitor and a second capacitor respectively. The first and second capacitors each have an independent electrode and share a common electrode. An AC voltage is applied to the common electrode producing first and second AC current signals at the two independent electrodes. A dual switched-capacitor integrated circuit and two current to frequency converters respectively convert the first and second AC current signals to first and second frequency signals having values f.sub.1 and f.sub.2. A microprocessor receives the first and second frequency signals and calculates R from f.sub.1 and f.sub.2.

Growing community of inventors

Sagamore Hills, OH, United States of America

Brian D Hemphill