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Download ebook Technologic Papers of the Bureau of Standards Volume 123-130

Download ebook Technologic Papers of the Bureau of Standards Volume 123-130

Technologic Papers of the Bureau of Standards Volume 123-130 by United States Bureau of Standards
Technologic Papers of the Bureau of Standards Volume 123-130
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Author: United States Bureau of Standards
Page Count: 66 pages
Published Date: 01 May 2012
Publisher: Rarebooksclub.com
Publication Country: Miami Fl, United States
Language: English
ISBN: 9781231326145
File size: 24 Mb
File Name: Technologic.Papers.of.the.Bureau.of.Standards.Volume.123-130.pdf
Download Link: Technologic Papers of the Bureau of Standards Volume 123-130
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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. 1919 Excerpt: ...mile, a slight error in the measurements would be exaggerated in the result. Errors might result from inaccurate readings or from different rail weights or resistivities. It is necessary, therefore, to make not only one measurement on each of the four rails at both stations, but measurements should be made at several slightly different locations at each station. In determining the average potential difference between the track and the earth, voltage measurements should be made to as many different underground structures as can be found in the vicinity. Measurements made to the water hydrants along the track are likely to give erroneous results, due to the gradient on the water main caused by the return current. The most reliable and consistent results were obtained by driving a ground rod into the earth at a distance of not less than 50 feet from the track and measuring the potential difference between it and the track with a high resistance voltmeter. This differential method was employed on the Wisconsin Avenue line in Washington at two different locations, designated as (a) and (b) in Table 1, and on the Chevy Chase line in three different locations, designated as (c), (d), and (e) in Table 1. The measurements extended over a period of two years and were taken under different moisture conditions of the roadbed. 2. ISOLATION METHOD OF MEASURING ROADBED RESISTANCE Some of the suburban roadbeds on which it was desired to make measurements were in localities where no piping systems existed and where the method just described could therefore not be employed. These roadbeds were of open construction and it was therefore a comparatively simple matter to remove the joint plates and bonds from four joints, thus isolating a section of track on which accurate and r...

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