A Universal Four-Pair Impedance Bridge

A wide range 10 ppm four-terminal-pair audiofrequency impedance bridge is described. The bridge can be operated either in an impedance mode, for self-inductance, mutual inductance, and resistanre measurements; or in an admittance mode for capacitance and conductance measurements. The frequency range for full aecuracy is 40 Hz to 2 kHz. Maintenance of the calibration of the bridge is facilitated by the use of transformer ratios to extend the range of a small number of precision components, and extensive use is made of electronic techniques to automate auxiliary balances.