IMPEDANCE MEASURING DEVICE AND CONTROL METHOD FOR IMPEDANCE MEASURING DEVICE

An impedance measuring device outputs an AC signal having a predetermined frequency to each of a positive electrode terminal and a negative electrode terminal of the fuel cell. The impedance measuring device includes a detection unit that detects an AC potential difference between the positive electrode terminal and a midpoint of the fuel cell, and an adjustment unit that adjusts an amplitude of the AC signal to adjust a detection signal to a predetermined value. The impedance measuring device includes an in-phase component extraction unit that multiplies the detection signal by an in-phase signal and extracts a resistance component of the detection signal, and a calculation unit that calculates a positive real axis impedance on the basis of the resistance component and the output signal. The impedance measuring device includes an orthogonal component extraction unit that multiplies the detection signal by an orthogonal signal and extracts a capacitance component of the detection signal, and a reproduction unit reproduces a vector value of the detection signal on the basis of the extracted capacitance component and resistance component. The adjustment unit adjusts the amplitude of the AC signal so that the reproduced vector value equals the predetermined value.