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Nalder Bros., and Thompson, Ltd., 34, Queen Street

London, E.G., and Kingsland Green, Dalston, London, N.E.

Electrical Instruments.

“ Soft-Iron ” Ammeters and Voltmeters for Continuous and Alternating Current (Fig. 1).—These instruments are made in a large variety of styles and sizes. In round cases, equivalent to dials of a diameter of 3 ins., 5 ins., 6 ins., and 8 ins., also sector patterns with scale lengths of 5 ins., 7 ins., 9 ins., and 12 ins., with either plain or illuminated dials; and edgewise pattern with 5 in., 8 in., and 12 in. scales. The last size can be made with illuminated dial.

Dead-beat soft iron Instrument, 3 in. dial. Fig. 1.

The cases are of black enamelled iron, with nickel or copper finish, or, in 6 ins. and 9 ins. dials, with brass cases.

In all cases the scales are of white enamelled metal.

In the case of ammeters a practically even scale is obtained from TV of the full load current upwards, in voltmeters the scale is opened at the working point and reads from | of the top scale reading.

The usual controlling force is “ gravity,” but the instruments are fitted with “ spring control” for marine, locomotive or portable use.

The instruments work on the principle of the repulsion of two similarly magnetised pieces of soft iron, the one being fixed, and the other carrying the pointer being free to move.

H 2

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