Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1975-04-28
1976-07-20
Krawczewicz, Stanley T.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 59, 324 60R, G01R 2700
Patent
active
039709256
ABSTRACT:
Apparatus for producing an indication of the value of an unknown capacitance or inductance, which employs a variable frequency oscillator producing a sinusoidal output which is fed through a resonant circuit comprising a reactive circuit element of known value selected to attain resonance with the unknown reactor within the oscillator frequency range. A phase detector measures the phase shift between oscillator output voltage and output current, and its direction and supplies a phase shift signal specifying this information to a controller which supplies a frequency control signal to the oscillator. The controller varies the frequency control signal responsive to the phase shift signal to eventually reduce phase shift to 0.degree. or other predetermined value indicating the resonance condition in the circuit. In a preferred embodiment, a series resonance circuit is formed by the known and unknown reactors, and phase shift between oscillator voltage and current is detected by measuring the phase angle of the voltage across the oscillator with respect to that across the capacitor in the series circuit, which angle must be 90.degree. at resonance. This embodiment is particularly well suited to measurement of small inductances in circuits having an appreciable amount of DC resistance.
REFERENCES:
patent: 3480857 (1969-11-01), Bialko et al.
patent: 3771050 (1973-11-01), Golahny et al.
patent: 3840805 (1974-10-01), Martyashin et al.
Procter Samuel Anderson
Younger Robert Dewitt
Control Data Corporation
Krawczewicz Stanley T.
Schwarz Edward L.
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