Reassessment of the Measurement Uncertainty of the XT-90 Twin T Dual Admittance Bridge

摘要

This memorandum supplements and updates the original report on the Twin T Bridge which was written over thirty years ago. An explanation of both the practical and theoretical circuit development is given leading up to an equivalent circuit and the bridge balance difference equations. A brief description of the calibration procedures used is given, together with details of the method used to measure standards at RSRE. Finally, a new assessment of overall bridge measurement uncertainty has been made, and a single equation for this produced for each of the free frequencies at which standards are currently calibrated. (Author)