Bulletin of the Bureau of Standards Volume 8 (Paperback)


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. 1913 Excerpt: ...deflection (about 0.2 per cent), which would be below the usual limit of reading. This error is compensated (at settings of the main dial near the upper limit) by the use of a fine rheostat in the galvanometer circuit, as shown in the diagram of connections (Fig. 2, p. 430). These two rheostats are combined, a single contact lever running over both spirals. A numerical example (given in the following seven pages) will illustrate the general method of design. It is desired to have a fundamental range of 1.5 volts, which must be readable directly to a part in 1,500, and by estimation of tenths of a galvanometer division, to a part in 15,000. One scale division is thus to equal 1.5+ 1,500=0.001 volt; hence by (34) /2 = 0.001 By modifying an existing type of galvanometer this value of Ilr was obtained. The value of / (current in amperes per scale division) was 0.00001; hence, r 0.001, 2 r=-= 100 ohms. 0.00001 The coil was critically damped for this value of the total resistance of the galvanometer circuit, and this total is over 10 times the coil resistance; hence the galvanometer fulfills the requirements. The period is about 1.2 seconds. The only improvement which would be desirable is that of a higher value of Ir, 100 ohms not being as high as is desirable. Of the 100 ohms, 40 ohms will be assigned to "external" resistance (volt box or shunt); adding 10 ohms for galvanometer resistance and 10 ohms for the calibrating coil gives 60 ohms; 100--60 = 40 ohms is thus available for "internal" resistance. The range being over 1 volt, and a single storage cell being evidently sufficient, the resistance of the potentiometer wire rw plus the constant resultant of rheostats r, and r, in parallel will be 4X40=160 ohms. The resistance of the main dial...

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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. 1913 Excerpt: ...deflection (about 0.2 per cent), which would be below the usual limit of reading. This error is compensated (at settings of the main dial near the upper limit) by the use of a fine rheostat in the galvanometer circuit, as shown in the diagram of connections (Fig. 2, p. 430). These two rheostats are combined, a single contact lever running over both spirals. A numerical example (given in the following seven pages) will illustrate the general method of design. It is desired to have a fundamental range of 1.5 volts, which must be readable directly to a part in 1,500, and by estimation of tenths of a galvanometer division, to a part in 15,000. One scale division is thus to equal 1.5+ 1,500=0.001 volt; hence by (34) /2 = 0.001 By modifying an existing type of galvanometer this value of Ilr was obtained. The value of / (current in amperes per scale division) was 0.00001; hence, r 0.001, 2 r=-= 100 ohms. 0.00001 The coil was critically damped for this value of the total resistance of the galvanometer circuit, and this total is over 10 times the coil resistance; hence the galvanometer fulfills the requirements. The period is about 1.2 seconds. The only improvement which would be desirable is that of a higher value of Ir, 100 ohms not being as high as is desirable. Of the 100 ohms, 40 ohms will be assigned to "external" resistance (volt box or shunt); adding 10 ohms for galvanometer resistance and 10 ohms for the calibrating coil gives 60 ohms; 100--60 = 40 ohms is thus available for "internal" resistance. The range being over 1 volt, and a single storage cell being evidently sufficient, the resistance of the potentiometer wire rw plus the constant resultant of rheostats r, and r, in parallel will be 4X40=160 ohms. The resistance of the main dial...

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Product Details

General

Imprint

Rarebooksclub.com

Country of origin

United States

Release date

March 2012

Availability

Supplier out of stock. If you add this item to your wish list we will let you know when it becomes available.

First published

March 2012

Authors

Dimensions

246 x 189 x 11mm (L x W x T)

Format

Paperback - Trade

Pages

198

ISBN-13

978-1-130-81795-9

Barcode

9781130817959

Categories

LSN

1-130-81795-4



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