Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Frequency of cyclic current or voltage
Patent
1979-07-06
1981-07-14
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Frequency of cyclic current or voltage
324 59, 324 60C, 324 62, 324DIG1, G01R 2700, G01R 2726, G01R 2702
Patent
active
042789320
ABSTRACT:
An a.c. bridge has a first arm with standard resistance, a second arm with a standard reactance element, a third arm having terminals for connection to an unknown impedance, and a fourth arm comprising a resistive circuit having first and second variable resistive elements. An a.c. supply voltage is coupled between the junction of the first arm with the second arm and the junction of the third arm with the fourth arm. First and second phase-sensitive rectifiers are coupled between the junction of the first arm with the third arm and a variable tap on the second resistive element in the fourth arm. The first rectifier is synchronized to a first a.c. reference signal in phase quadrature with the voltage across the unknown impedance, and the second rectifier is synchronized to a second a.c. reference signal in-phase with the voltage across the unknown impedance. Indicators are coupled to the outputs of the rectifiers for indicating the senses of their output signals. The first resistive element can be adjusted until the phase difference between the unbalance signal at the input of the first rectifier and the first a.c. reference signal is at a predetermined value and the second resistive element is subsequently input of the second rectifier and the second a.c. reference signal is at a predetermined value without affecting the phase relation between the signal at the input of the first rectifier and the first a.c. reference signal to balance the bridge.
REFERENCES:
patent: 2968180 (1961-01-01), Schafer
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