The present invention provides an AC bridge with an automatic auxiliary balancing function and an impedance measurement method. The AC bridge comprises the following components: an
AC power supply, a main inductive
voltage divider, an auxiliary inductive
voltage divider and a null indicator. The main inductive
voltage divider and the auxiliary inductive
voltage divider have a same inductive voltage dividing ratio. A
negative feedback branch circuit which is obtained through serially connecting an active voltage follower, an inverting
amplifier, a wave filter and an insulating
transformer is arranged between the main inductive
voltage divider and the auxiliary inductive
voltage divider. An original edge of the insulating
transformer is connected with the auxiliary inductive voltage divider. The input end of the active voltage follower is connected with the main inductive voltage divider, and the output end is connected with the null divider. According to the measurement method, after the divided voltage on the main inductive voltage divider is processed by the
negative feedback branch circuit, the
branch circuit of the null indicator automatically acquires ground potential. The bridge can realize impedance comparing measurement through a simple main balance. The AC bridge of the invention realizes accurate and quick
AC impedance measurement and greatly improves convergence rate of the AC bridge.