Helium Research Center internal report
Subtitle: an RC bridge and detector for the measurement of small capacitance changes
By: by J.R. McVey and J.L. Gordon
Contributors: Gordon, J.L.; United States. Bureau of Mines; Helium Research Center (United States. Bureau of Mines). Branch of Fundamental Research
Series: Helium Research Center Internal Report / U.S. Department of the Interior, Bureau of Mines -- no. 51; Helium Research Center Internal Report (United States. Bureau of Mines) -- no. 51.
Publisher: U.S. Department of the Interior, Bureau of Mines, Branch of Laboratory Services
Published: 1964
Place of publication: Amarillo, Tex
Language: eng
Number of pages: 17
Subjects: Helium; Capacitance meters; Dielectric measurements; Design and construction
Other titles: Bureau of Mines, Helium Activity, Helium Research Center Internal Report; RC bridge and detector for the measurement of small capacitance changes
Description: An instrument for the purpose of detecting small changes in air dielectric capacitance is described. It consists of an RC bridge circuit with the associated power supply and detector. The bridge has a 26 VAC input and sine wave output which is compared with a square wave in the detector. The dc output from the detector is a measure of bridge unbalance in millivolts, with a minimum sensitivity of 10́℗đ pico-farads at 200 pico-farads. The bridge and detector assembly were designed to monitor the rate of diffusion of gases and were used successfully for this purpose. A small change in gas mixture composition changes the gas-dielectric constant; therefore,  the capacitance value of a small air-type capacitor inserted into the gas mixture changes proportionally, and is recorded as a function of time.
Notes: "June 1964."

"Branch of Laboratory Services, Project 820.1."

Includes bibliographical references (leaves 9-10).