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D.C. Ammeter, Type R

Unidentified · Physics

The ammeter is set in a square, wooden, varnished stand, with a simple flat base and a vertical wood panel with the ammeter’s case set through it. A pair of triangular braces support the vertical piece on either side, sloping backwards.

The ammeter itself is cylindrical with a round face. A arc-shaped scale is in the top section of the face; the scale, set behind glass, runs from 0-20, calibrated in millamperes and labelled from 10-0-10, with zero at the centre. There is an indicator needle at rest pointed at zero. Beneath the scale on the black face of the ammeter, there is a maker’s mark and information about the instrument.

Two large posts emerge from the rear of the ammeter case. These are connected by plastic-insulated wires to a pair of electrical terminals affixed to the base. The two terminals are labelled with “+” and “-” symbols. The wire that runs to the positive terminal runs through a fuse before reaching the ammeter.

Accession Number:

Alternative Name:

Primary Materials: Wood, Metal, Glass


Old inventory number = phy1024. This is handwritten on a pale yellow note that is stuck to one of the triangular supports of the stand.

The face of the ammeter has raised lettering which reads: “Wagner Electric Mfg. Co.”, “Type R”, “St. Louis, U.S.A.”.

Handwritten in black ink on the rear of the wooden stand, above the ammeter case: “10-0-10 MILLAMPERES”

Dimensions (cm):

Height = 33 cm, Width = 30 cm, Length = 29 cm


Measuring amperage in an electrical circuit; possibly a demonstration device.


Very Good: The wooden stand is in good condition, although in places, particularly on edges and corners, the varnish is chipped. There are a few small scratches on the surface of the wood. The bronze-coloured metal surface of the front of the ammeter is somewhat oxidized (dulled). The scale and case is otherwise in excellent condition.

Associated Instruments:


Wagner Electric Manufacturing Company, St. Louis, Missouri, USA

Date of Manufacture: 1891-1967 (likely before 1930)


Department of Physics, University of Toronto

Additional Information and References:

Historical Notes: