Hawkins electrical guide Volume 2 ; Questions, answers & illustrations a progressive course of study for engineers, electricians, students and those ... and its applications a practical treatise - Softcover
Synopsis
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. 1917 Excerpt: ...with the position of the plug at the left of the instrument indicates the voltage under test. As directed above, use key Ri for rough adjustment, Rj for intermediate adjustment, and key Ro for final adjustment. Plug at 1 gives readings for voltage directly from settings of tenths switch and extended wire contact. Plug at.1 shunts the potentiometer circuit so that the voltage measured is.1 of the reading taken directly from the scale. Hence, the readings taken from the setting of the tenths switch and the slide wire contact must be divided by 10. Fig. 615.--To measure a pressure greater than 1.6 volts with Leeds and Nothrup potentiometei by using a volt box or multiplier. To measure high voltages it is necessary to connect the voltage across high resistance and to measure on the potentiometer a definite fraction of the total drop. In the figure, AB is a high resistance of which CB is.1th, DB,01th, and EB.001th of the total resistance. The potentiometer reading is accordingly multiplied by 10, 100, or 1,000, depending upon whether the switch M is set on C, D, or E. Resistance boxes lor this purpose are called volt boxes, and are constructed to multiply the potentiometer readings by 10, 100, and 1,000. In using them, it is only necessary to connect the unknown E.M.F. at the posts so marked, and the potentiometer to the posts marked P. The potentiometer reading is taken as above and multiplied by a factor depending upon the position of the switch M, which factor is indicated upon the box. // is essential in making these connections that the polarity be carefully observed. To Balance Galvanometer for Unknown Voltage.--Place plug in hole 1 (fig. 610) for voltages up to 1.6, and in hole.1 for voltages up to.16. Rotate the tenths switch until a condition of balance...
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