Patent ID: 8473232

Claim:
A measuring apparatus comprising: a voltage injecting unit that injects a test AC signal into a measured circuit by applying an AC voltage to an injection coil; a current detecting unit that uses a detection coil to detect an AC current flowing in the measured circuit due to injection of the test AC signal and outputs a detection signal whose amplitude changes in accordance with an amplitude of the AC current based on a current detection signal outputted from the detection coil; a processing unit that calculates a current value of the AC current based on the detection signal and calculates at least one of a purely resistive component and a reactance component of the measured circuit as measurement values based on the calculated current value of the AC current and a voltage value of the injected test AC signal; a first signal generating unit that generates and outputs a first signal that has a same period as a fundamental wave of the AC voltage and is synchronized with the fundamental wave of the AC voltage; and a second signal generating unit that generates and outputs a second signal whose phase is perpendicular to the first signal, wherein the current detecting unit carries out synchronous detection on the current detection signal using the first signal and outputs a first detection signal whose amplitude changes in accordance with an amplitude of a real component of the AC current as the detection signal and carries out synchronous detection on the current detection signal using the second signal and outputs a second detection signal whose amplitude changes in accordance with an amplitude of an imaginary component of the AC current as the detection signal, and the processing unit executes: a resistance value calculating process that calculates an absolute value of the current value of the AC current based on the first detection signal and the second detection signal and calculates an absolute value of an impedance of the measured circuit based on the calculated absolute value and the voltage value of the test AC signal; a phase angle calculating process that calculates a phase angle between the AC current and the test AC signal based on the first detection signal and the second detection signal; and a measurement value calculating process that calculates the measurement values based on the calculated absolute value of the impedance and the calculated phase angle.