Inductive Voltage Dividers with Calculable Relative Corrections

Inductive voltage dividers are now used in measurement laboratories for the production of audio-frequency voltage ratios with errors (deviations from turns ratio) of a few parts in ten million of input. A major component of error arises from the interaction between distributed shunt impedances and leakage impedances in the windings. Correction for this systematic error in dividers of special design can result in an order-of-magnitude improvement in accuracy. A solution using network equations has been obtained for the corrections to the relative errors of inductive voltage dividers of specific design. Earlier theoretical considerations, confirmed by measurements of limited accuracy, indicated an S-shaped curve of ratio error vs nominal ratio, and quadrature component vs nominal ratio. The results from recent calculations are in agreement with the earlier measurements and provide much better definition of the true shape of the S-curve. An algebraic equation has been derived for the limiting form of this S-shaped characteristic curve. A resistance analog of an inductive voltage divider was constructed to represent the lumped circuit parameters equivalent to the distributed shunt admittances and the winding impedances. Measurements of the gross errors in the analog have yielded experimental results in excellent agreement with those calculated from the network equations.