Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Patent
1988-12-19
1990-05-01
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
324 79D, G01R 23165
Patent
active
049221957
ABSTRACT:
An extraneous frequency detector especially suited for analyzing the three-phase output of a variable speed constant frequency (VSCF) generator generates in a sample-and-hold circuit amplitude samples of a phase selected by a multiplexer for application to a discrete time analog filter in the form of a switched capacitor high pass filter. A control circuit generates dual-phase non-overlapping clocking signals which control the sampling rate of the sample-and-hole circuit and the switching rate of the switched capacitor filter. Two modes of operation are provided for the single filter circuit by generating the clocking signals for the first mode of operation at a first frequency which is at least twice the frequency of the highest order harmonic of interest such that all frequencies above the fundamental are detected. In the second mode of operation, the clocking signals are generated at the fundamental frequency. This produces aliasing of the fundamental frequency and all harmonics resulting in a comb filter which detects all frequencies above a few hertz except for the fundamental and its harmonics. The selected frequency is preferrably a power of two multiple of the fundamental frequency such that a divider circuit generates the clocking signals at fundamental frequency from the pulses at the selected high frequency. A peak detector provides an output signal representative of the highest amplitude of the frequencies passed by the filter.
REFERENCES:
patent: 4197515 (1980-04-01), Hornfeldt et al.
patent: 4313096 (1982-01-01), Fleischer
patent: 4326261 (1982-04-01), Peoples
patent: 4471299 (1984-09-01), Elmis
patent: 4794369 (1988-12-01), Haferd
patent: 4803650 (1989-02-01), Nashimura et al.
Ted W. Pickerrell, Designing Low Frequency Filters on the CMOS Monochip, 1983, Monochip Application Note APN-28, Interdesign, a Ferranti Company.
Karlsen Ernest F.
Urban Edward
Westinghouse Electric Corp.
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