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. 1918 Excerpt: ...in Figs. 105 and 107 are not suitable for working at pressures above 8,000 volts (alternating), since a brush discharge is liable to occur from the edges of the moving vane, even if rounded off and separated from the fixed vanes by a wide gap. In such cases, therefore, it is advisable either to adopt some means of ...
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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. 1918 Excerpt: ...in Figs. 105 and 107 are not suitable for working at pressures above 8,000 volts (alternating), since a brush discharge is liable to occur from the edges of the moving vane, even if rounded off and separated from the fixed vanes by a wide gap. In such cases, therefore, it is advisable either to adopt some means of extending the range without applying the whole pressure to the' vanes or to adopt an entirely different design. Peukert1 showed that the range of an electrostatic voltmeter could conveniently be extended by connecting one or H v H Fig. 108.--Extension of Range of Electrostatic Voltmeter by means of Condensers. more condensers in series with it. In another arrangement a number of condensers are connected in series with each other across the pressure to be measured (V), and the voltmeter itself is joined across one of the series, as shown in Fig. 108. The use of condensers is convenient for switchboard work, but the utmost care must be taken to guard against even a minute leakage across the instrument or the condensers. If this point is not attended to, the readings are liable to be greatly affected by change of frequency and, as it is impossible entirely to eliminate leakage, electrostatic voltmeters whose range has been extended by the use of 1 EkctrotechnUche ZeiUchrift, Vol. 19, p. 50. condensers are not applicable to varying frequencies, nor, of course, can they be used on continuous current systems. A further matter of importance is the effect of the capacity of the leads employed to join the condenser to the instrument. It must be remembered also that all parts of the apparatus possess a capacity to earth which may produce a different effect on the potential between the vanes according to the relative potential between either pole and earth. ...
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