Congressional Edition Volume N . 6267
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 edition. Excerpt: ...are somewhat greater, as might be expected. Two of these laboratories are undertaking the construction of new standards in accordance with the more rigorous London specifications here employed. The comparison of the new tubes with the Bureau tubes will furnish a better basis for estimating the accuracy attainable in the reproduction of the international ohm. PRECISION RESISTANCE MEASUREMENTS. This work includes the investigation of methods of resistance measurements, the design and investigation of resistance standards, the determination of the various electrical properties of conductors and the testing of resistance standards, bridges, precision rheostats, potentiometers, etc. During the past year there has been an increase in the number of resistance standards and other apparatus tested. Apparatus for the accurate establishment of a resistance ratio of 10 to 1 has been constructed according to the Bureau specifications and now replaces the apparatus formerly used in "building up." A few resistance standards have been constructed, using a new alloy. While these have been under observation only a few months, the indications are that the new alloy will be found to be as good or better than manganin for use in resistance standards and resistance apparatus. A study has been made both of resistance standards having four terminals and of the Thomson bridge. The results of this investigation are to be published in the Bulletin of the Bureau. ELECTRICAL MEASURING INSTRUMENTS. During the year an extended investigation of direct current switchboard instruments was completed and the results prepared for publication in order to make the detailed data available to manufacturers and users of instruments. An electrodynamometer capable of carrying...
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