Patent GB-189721157-A (GB)
Title: Magnetic and Electric Measuring Instruments.
Inventor: RUSSELL JAMES
Filed: 1897-09-15
Granted: 1898-07-16
Abstract: 21,157. Russell, J. Sept. 15. Current and energy meters; magnetic measurements. - Am-meters may be constructed as shown in sectional plan in Fig. 2. The current passes through four stationary rectangular coils A, A, B, B. Two of these B, B are arranged vertically and produce a uniform horizontal magnetic field ; the other two A, A are connected so that the current flows in the same direction in all the adjacent wires in the middle. These wires are magnetically shielded to some extent by surrounding iron I, which is carried by a balanced frame F, and can move vertically to some extent. The balance is provided with movable weights to measure the effect of the current on the iron I. The windings may be modified for use of the instrument as a volt-meter or watt-meter, with continuous or alternating currents. The iron I may be in thin strips bent into U-form, and placed together from above and below the balance frame, with insulation interposed between the overlapping limbs. The instrument may be used for observation of the properties of different specimens of iron, and may be provided with current reversing and regulating switches. The iron may be stationary, and the coils A, A movable, in which case these coils may be enlarged to enclose the stationary coils B. The coils B may be replaced by other means for the production of a uniform magnetic field. The parts may be duplicated at the ends of the frame F, so that the instrument may be used to balance the effects of two specimens of iron, one of which may be a standard piece. The balance may be replaced by a part hung by a torsion wire, as shown in vertical section in Fig. 7. In this form, a single coil A, partly shown, of D-form in plan, is used. The coils B, B are circular, the torsion wire M being placed axially in them. The wire M carries a short straight tube L, enclosing a straight part of the coil A, and carrying a pointer R. Two iron specimens may surround or partly surround the ends of this tube, when the difference of their magnetic effects is to be observed ; or iron may be placed on one end only. In a modification of this instrument, the coils B are modified to act in the same direction on iron at both ends of the tube L. For measurement of large currents, thick strips may be used instead of wire coils. Fig. 11 shows a front elevation of such an instrument. The current, supplied through a conductor E at some distance behind the front portion, divides through two strips A, A<111>; the current from the part A<111> passes through a horizontal semicircular part B<11>, a vertical part A<1>, another semicircular part behind that shown at E<111>, and a vertical part A<11111>; the current from the strip A passes through parts symmetrical with these. The four semicircular parts replace the coils B, and the vertical parts the coils A, and they act on iron pieces H carried by a support L hung by a torsion wire. The support L may carry a damping- vane in a vessel of oil. The method of using conductors partly shielded magnetically may also be applied in sensitive galvanometers and other modifications of the instruments described.