Calibration of IVDs at frequencies up to 1MHz by permuting capacitors

A device has been constructed which permutes eleven nominally equal 50pF capacitors in a bridge to calibrate the 10:1 and 1:10 ratios of inductive voltage dividers (IVDs) at frequencies up to 1MHz. A compact design, which is important for high frequency measurements, was implemented using printed circuit boards and ceramic NPO dielectric capacitors. The capacitors are individually shielded to reduce errors from stray capacitances. Comparisons made with results from an existing NPL method of calibrating IVDs at frequencies up to 100kHz and with results from a recently developed high-frequency four terminal-pair bridge show that better than 10 parts-per-million uncertainty has been attained at 1MHz.