Wire electrometers are less sensitive by about two orders of magnitude than those with quadrants, but they have the advantage of bringing together great speed, great simplicity of use and good stability. For these reasons they were favoured over quadrant electrometers in all cases in which sensitivity as great as that of quadrant electrometers was not required.
In the Lutz-Edelmann electrometer the auxiliary field is created by a pair of steel electrodes with a triangular cross section, arranged vertically and well isolated, with two edges, lengthened by a slight curvature of the lateral faces, placed side by side (blades).
Between the two blades there is a very thin platinum wire which is held taut by an insulating quartz reed and an elastic string, it too made of quartz, closed in a loop.
The blades and the wire are protected and insulated by a metal case which is earthed. In the symmetrical connection, which is the most widely employed, the two blades are maintained at equal and opposite potentials of about one hundred volts by connecting them to a battery, the central point of which is earthed. By moving the blades closer together or farther apart, it is possible to create a more or less intense field between them....continues