Abstract
To meet the demand for increased precision a new standardizing capacitance bridge, known as the No. 12 type, has recently been developed by the Bell Telephone Laboratories and is now described by W. D. Voelker (Bell Lab. Rec, 20, No. 5 ; 1942). This bridge, operating at frequencies up to 200 kc, has a range of from 0 to 1-11 u F., and from 0 to 1000 umhos. It is of the equal-ratio-arm type, the arms being of woven-wire resistance. A slide wire at the junction of the two resistances and an air condenser that allows capacitance to be shifted from one arm to the other, permit a small amount of adjustment that may be required at infrequent intervals to offset the effects of ageing. The resistances form the adjacent ratio arms of the bridge, and permit an unknown capacitance in a third arm to be measured against an adjustable standard capaci-tance in the fourth. This is the basic principle of the bridge. Conductance standards are included in the bridge. For measuring the larger values of capacitance silvered-mica condensers are employed as standards, while for smaller values of capacitance, air condensers are more convenient. The air-condenser standard consists of three decades of fixed capacitance and a movable plate condenser for fine adjustment. The control dial is calibrated to indicate directly the capacitance of the unknown for each position of the dial.
Article PDF
Rights and permissions
About this article
Cite this article
An Improved Capacitance Bridge for Precision Measurements. Nature 149, 468 (1942). https://doi.org/10.1038/149468b0
Issue Date:
DOI: https://doi.org/10.1038/149468b0