Helium Research Center internal report
a 10-channel automatic scanner with individually selectable channel times
by James R. McVey
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A 10-channel automatic scanner has been developed to automate a thermal conductivity apparatus used in the direct analysis of helium-nitrogen and helium-hydrogen gas samples from a phase equilibria apparatus. The unit uses unijunction transistors to provide a separate programmable time of 1 to 99 seconds for each individual channel. Individual channel timing allows the user to program measurements and/or command functions at will. The unique features of the unit are its individually programmable channel time and its compatibility with commercial digital voltmeters and printers. These features permit the scanner to completely automate the sequence of events from sample injection to the printing of the final sample results from the thermal conductivity apparatus.
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1
Helium Research Center internal report: a 10-channel automatic scanner with individually selectable channel times
1968, U.S. Department of the Interior, Bureau of Mines, Branch of Laboratory Services
in English
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2
Helium Research Center internal report: an RC bridge and detector for the measurement of small capacitance changes
1964, U.S. Department of the Interior, Bureau of Mines, Branch of Laboratory Services
in English
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3
Helium Research Center internal report: a digital pressure-readout device
1964, U.S. Department of the Interior, Bureau of Mines, Branch of Laboratory Services
in English
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Book Details
Edition Notes
"October 1968."
"Branch of Laboratory Services, Project℗7751."
Also available online via Internet Archive.
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Work 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.
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| October 3, 2019 | Created by ImportBot | Imported from Internet Archive item record |