The use of 1:1 comparator bridge for 10:1 and 1:10 inductance standard transfer

An idea of using 1:1 high-precision comparator bridge for 10:1 and 1:10 impedance transfer is described in this paper. The procedure described in this paper was applied to transfer the unit of inductance from 10 to 1 mH, and from the 1 mH to the 100-μH standard inductor. A symmetric summing branch-joint was designed especially for adding in a series up to three GenRad-type standard inductors, and thereby enables the transfer. Uncertainty analysis and results of measurements performed for 10:1 transfer of inductance are presented. The analysis and the results achieved prove that using 1:1 impedance comparator bridge and applying proposed procedure is possible to transfer the unit to the objects of 10 times smaller values with relative standard uncertainty only a dozen percent higher than relative uncertainty estimated for 1:1 comparison of the standards having nominal values as the wanted standard. The idea presented here for inductance comparison is universal and can also be applied for other kinds of standards compared in National Metrology Institutes.