An Automated Co-Axial Ac Resistance Bridge

An automated co-axial ac bridge has been constructed, by substituting automated inductive voltage dividers (autoIVD's) for manual dividers in a standard 4 terminal-pair bridge design. The bridge has been used to measure the ratio of two 100 Omega resistors. A Tinsley 100 Omega ac/dc resistor has been found to change value by 0.1 parts per million (ppm) from 500 Hz to 2500 Hz, with a type A uncertainty of 0.025 ppm