A bridge for the measurement of permittivity

A description is given of a null method for the measurement of the complex permittivity of dielectrics. The direct admittance of a 3-terminal capacitor with the sample as dielectric is measured as a complex capacitance, the two components being indicated directly on two 3-terminal variable air capacitors. In addition to these the bridge network comprises transformer ratio-arms and an amplifier whose output voltage is in quadrature with that of the transformer. The bridge operates at ten fixed frequencies from 30 to 106 rad/sec.