Square-wave-source gated-detector bridge system for the precise measurement of resistance

摘要

The design and performance of a square-wave system for the precise measurement of resistance are described. A 25 Hz square wave is applied to a conventional resistance bridge, and the output of the bridge is sampled, after the decay of transients owing to reactances, by a gated detector. A single adjustment is sufficient to balance the bridge, and the balance is independent of thermal electromotive forces. The system is suitable for platinum-resistance thermometry, and a square-wave-to-d.c. error of less than 10 ???????????????? may be obtained in the resistance range 0????????100 ????????.