An Automatic High-Precision Audiofrequency Capacitance Bridge

A compact transformer-ratio-arm bridge has been built in which the balance point is automatically determined with the aid of an internal microprocessor. The instrument described in this paper can operate from 20 Hz to 20 kHz, and has three ranges; 12, 120, and 1200 pF. The instrument can resolve one part in 108 of full scale above 400 Hz, and can be fully controlled over its IEEE-488 bus interface.