The Twin-T A New Type of Null Instrument for Measuring Impedance at Frequencies up to 30 Megacycles

A null instrument for measuring impedance at high frequencies is described. The circuit used is of the parallel-T, rather than of the conventional bridge type. The inherent adaptability of this circuit for use at high frequencies makes possible an upper frequency limit of 30 megacycles, which is considerably higher than that previously obtainable in commercial types of null instruments. The residual parameters causing error are noted and measures taken to minimize them discussed. Methods of measuring them and of correcting for their effects are given.