Accession No

4306

Brief Description

Electrodynamic type suspended coil ammeter by Siemens Brothers & Co., 1900–1910

Origin

London

Maker

Siemens Brothers & Co.

Class

electrical

Earliest Date

1900

Latest Date

1910

Inscription Date

Material

wood; metal (brass, copper, mercury, white metal and at least one other); glass; liquid; plastic (ivorine and at least one other); graphite; rope (fibre); cloth (felt, silk)

Dimensions

diameter of base 190mm; height 325mm

Special Collection

Cambridge Instrument Company Collection

Provenance

Donated by the Cambridge Instrument Company.

Inscription

‘SIEMENS BROS. & CO.
LONDON’ (dial)
‘TR NO 28’ (base)
‘5272’ (side of base)

Description Notes

Circular wooden base with three brass levelling feet. Three brass terminals marked ‘1’, ‘3’ and ‘2’ on ivorine discs, providing two different current ranges when terminals 1 and 3 or 2 and 3 are used; brass clamping mechanism. Circular bubble level. Two brass stands supporting single fixed coil. Circular silvered glazed dial on top with full circle scale divided 0 - [400], numbered by 10, subdivided to 1. Metal knob and pointer on central shaft connected via spiral spring and silk suspension to the moving coil and attached pointer (knob is used to bring pointer on suspended coil back to zero position). Two cups hold mercury for electrical connections to moving coil. Cylindrical glass cover with circular felt-lined brass rings at top and bottom.

Condition good (brass knob tarnished); complete.

References

Events