Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1987-09-01
1988-11-22
Tokar, Michael J.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 78D, 324 83D, 377 19, G01R 2302
Patent
active
047868619
ABSTRACT:
A device and method for measuring the frequency of an input signal by measuring the number of cycles of the input signal that occur in a sample interval between successive sampling times t.sub.n. An integer counter determines an estimated integer number of input signal cycles, and fraction counters determine fractional counts by counting cycles of a clock signal during time intervals between a first measurement time before the sampling time and a second measurement time after the sampling time. A correction circuit refines the fractional counts by determining the phase relationships between the clock and input signals at each measurement time. The correction circuit includes a constant current source, a capacitor, a first switch connected between the constant current source and a reference potential, a second switch connected between the constant current source and the capacitor, and a control circuit for the switches. The control circuit disconnects the current source from the reference potential at each measurement time, and disconnects the current source from the capacitor upon the next occurance of a periodic characteristic of the clock signal that occurs after the measurement time. The voltage on the capacitor then provides the required phase relationship.
REFERENCES:
patent: 3928798 (1975-12-01), Valis
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patent: 4070618 (1978-01-01), Thomas
patent: 4073432 (1978-02-01), Schroder
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U.S. patent application Ser. No. 908,356, Vibrating Beam Accelerator with Velocity Change Output, filed 9/17/86, inventor R. B. Peters.
U.S. patent application Ser. No. 789,657, Synchronous FM Digital Detector, filed 10/21/85, inventor R. B. Peters.
Hulsing II Rand H.
Lee Charles K.
Sundstrand Data Control Inc.
Tokar Michael J.
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