GB322558A - Improvements in electric meters - Google Patents

Abstract

322,558. Wates, F. S. S. Sept. 20, 1928. Electromagnetic current and pressure meters. - A single meter is arranged to read high and low voltages and milliampers without the use of external shunts or of a switch to put resistances into circuit. A casing a has a contact spike a<1> connected thereto and two terminals a<2>, a<3>, of which the former is connected to the casing and the latter is insulated therefrom through the shank of a watch ring a<6> passes a pair of flexible leads b, c having contact spikes at their outer ends. The coil e of the meter, which have a resistance of 200 ohms, is carried by downwardly-turned lugs d<1> of a brass or other support d, on which is mounted a high resistance k<1> which may have a value of 4800 ohms. The moving iron f which is magnetized, is mounted on a pivot rod f<1> between the lugs d<1>, and carries a pointer f<2>. The movable iron f is returned to zero by means of a permanent control magnet j. On the inside of the coil former is painted some powdered magnetized iron so that a weak magnetic field is set up. The coil e is connected at one end to the casing and at the other end to the insulated terminal a<3>, one lead b, and one end of the resistance k<1>, the other end of which is connected to the other lead c. The dial of the instrument is marked with a scale of milliamperes and with high and low voltage scales. For measuring milliamperes the terminals a<2>, a<3> are employed. For measuring voltages the fixed spike a' and the spike connected to either the lead b, for low voltages, or the lead c for high voltages, employed. The meter may be arranged for panel mounting. Specification 249,954 is referred to.