File:X-ray manual - U.S. Army (1917) (14757286875).jpg

Identifier: xraymanualusarmy00unit (find matches)
Title: X-ray manual : U.S. Army
Year: 1917 (1910s)
Authors: United States. Surgeon-General's Office American Roentgen Ray Society
Subjects: X-rays Fractures Teeth Chest Heart Radiography
Publisher: New York : Middleditch
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ong as the power line is kept at the voltage pre-vailing when this line was determined the co-ordinatesof this line, give all the currents and voltages at anytime available on this rheostat setting. H gives thecurrents at which gaps between 6 and 3 inches are brokenon button H. Fig. 16 shows five such lines for a par-ticular machine on auto-transformer control. How to Use Such a Chart. Using chart, Fig. 15, one needs for a particular case20 M. A. at a 4-inch gap. The vertical line through 20cuts the line marked F at the 4-inch gap. Hence wemust use button F. Have spark gap at seven inches andforget it entirely. Move rheostat lever to F, look atyour milliammeter, use one hand on transformer pri-mary switch and the other on the Coolidge control. Closetransformer switch and bring filament control to asetting giving 20 milliamperes tube current; there is noneed of testing the spark gap. Do not try to read the milliammeter on the throw.Learn to start and set your machine within 10 seconds.
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Fig 15 Partial chart of a particular machine with rheostat (control.Note that gap change as tube current increases is very rapid. On G, for example,we have a 6 inch gap at 25 M.A. and only a 3 inch gap at 27.5 M.A. or a changeof an inch for each 2y2 M.A. Compare with Fig. 16. Gap 6 (ifKhti) 5432 , ■^■cr^ __^ jjH ~ _ — Hi :::.: L - ~ _4- ::: «£ tn* «^ n ■ —i gs r~ :: — M I :::: -+~r 0 10 20 30 40 SO 60 70 80 90 100 MA. Fig 16 Partial chart of the same transformer using auto-transformercontrol Note line marked P shows all useful currents that can be had on thissetting- changing from 5 M.A. to 50 M.A. lowers gap from 5 inches to 3. X-RAY PHYSICS 45 On 20 M. A. desired, a current of 19 or 21 M. A. is closeenough for this work. Using chart, Fig. 16, for 45 M. A. at a 4-inch gapgo at once to R and proceed as before. A little timespent in making this chart and in using it will reducetime lost and failures. Note that the faster the sparkgap falls with increase of tube current t

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