An AC Four-Terminal Low Value Resistance Bridge

This paper describes a current transformer based ac four-terminal low value resistance measurement bridge. The design and performance of this bridge is presented, which compares resistors from 10 to 0.1 ohm over a frequency range of 100 Hz-10kHz. The reference ratio arm used in this bridge is a special designed high accurate zero-flux current transformer (ZFCT). The current ratio value of the ZFCT is self-calibrated by using the conventional build up method. An auxiliary current transformer combined with variable impedance is used to constitute the wagner circuit.