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| Keywords: ChartersOfFreedom 033.jpg E C Creitz of the NBS Gas Chemistry Laboratory installing two of the leak-detecting cells sealed in the channel around the edge of the enclosure For each enclosure four cells were involved Two of these were sealed within the enclosure and two were located in the channel along with the enclosure edge By plugging the leak detecting meter into the leads of the four cells a small current energized the cells The circuit of these cells was so arranged so that the instrument compared the resistance of the four cells the two measuring cells with the two outside reference cells The comparison indicated whether any change had occured in the composition of the gas within the enclosure If a change had occured the cells were not in balance and the meter indicated a leak National Institute of Standards and Technology National Institute of Standards and Technology The images in the ChartersOf Freedom Photographic Collection are in the public domain and are not subject to copyright in the United States However please pay special attention to the individual works to make sure there are no copyright restrictions indicated Individual works may require securing other permissions from the original copyright holder Use of the images from NIST Digital Collections is not restricted but a statement of attribution is required Please use the following attribution statement National Institute of Standards and Technology Digital Collections Gaithersburg MD 20899 PD-USGov National Bureau of Standards National Institute of Standards and Technology United States Declaration of Independence | ||||
