Improvements in Ammeters.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Ammeters.
We, SIEMENS BROS. & Co. LD. of 12 Queen Anne's Gate, Westminster,
in the County of London, and JOHN NEBEL of 14 Little Hoath Villas, Old
Charlton, in the County of Kent, Electrical Engineers, do hereby declare the
nature of this invention to be as follows:-
This invention relates to a simple construction of ammeter, which is of the
following description.
On a horizontal spindle carrying a counterpoised index are fixed a pair of
equal opposite arms, each terminating like a T in a short axis parallel to the
spindle.
On each of these axes is mounted a light frame having attached to it a pair of
parallel iron wires one of these wires being on each side of a bar or other conductor
carrying the current to be measured. Instead of two separate wires, a single piece
of wire may be bent in the form of a hairpin with two parallel limbs.
Each wire is supported at its one end beyond the conductor on a roller or link
while the other free end does not extend so far as the other side of the conductor.
When a current passes through the conductor, the wires of the one pair are drawn
say to the left across the conductor, those of the other pair being drawn to the
right also across the conductor, both of the light frames to which they are attached
are thus caused to rock on their axes, which themselves move to the left and
right respectively, thus partly turning the spindle, in opposition to a spring
and moving the index along a graduated scale.
In order to provide for measuring currents of small amount, the conductor
may be arranged so as to make several convolutions including the wires.
Dated this 9th day of December 1896.
ABEL & IMRAY,
Agents for the Applicants.

page_text: nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
This invention relates to a simple construction of ammeter, which is of the
following description.
On a horizontal spindle carrying a counterpoised index are fixed a pair of
equal opposite arms, each terminating like a T in a short axis parallel to the
spindle.
On each of these axes is mounted a light frame having attached to it a pair of
parallel iron wires one of these wires being on each side of a bar or other conductor
carrying the current to be measured.
Instead of two separate wires, a single piece of wire may be bent in the form
of a hair pin with two parallel limbs.
Each wire is supported at its one end beyond the conductor on a roller or link
while the other free end does not extend so far as the other side of the conductor.
When a current passes through the conductor, the wires of the one pair are drawn
say to the left, across the conductor, those of the other pair being drawn to the
right also across the conductor, both of the light frames to which they are attached
are thus caused to rock on their axes, which themselves move to the left and
right respectively, thus partly turning the spindle in opposition to a spring,
and moving the index along a graduated scale.
On the accompanying drawings is shewn a construction of Ammeter according
to the above described invention.
Fig. 1 shews a front view partly in section on line Z Z Fig. 2.
Fig. 2 shews a section on line X X Fig. 1 and Fig. 3 a section on line Y Y.
A is a broad copper bar suitably mounted on insulated supports in a
casing B.
The bar A has a central opening through which passes a spindle C carried in
brackets D fixed on each side of the bar A. On the spindle C is fixed firstly a
balanced index E working over an ampere, scale, and secondly a pair of opposite
arms F with T heads F which constitute axes parallel to C and are mounted
between centres in light frames G. Each of these frames carries a fork of thin
iron wire H H¹ the limbs of which extend in opposite directions transversely
across both faces of the bar A, in such manner that when no current is passing
through A, the ends of H stop short at some distance from the right hand edge
of A, while those of H¹ are at a corresponding distance from the left hand edge
of A. For the purpose of supporting the other ends of the forks so as to allow
them perfect freedom of motion, they may either be pivotted to small wheels I
running between fixed guides J as at Figs. 1 and 3 or they may rest freely
upon the periphery of small wheels I mounted in brackets, as shewn in the
modification at Figs. 4 and 5, or again, they may be pivotted to the ends of
small radius rods K pivotted to the casing as shewn in the modification at
Figs 6 and 7.
The rotation of the axis C in the direction of the arrow Fig. 1 is resisted by
an adjustable volute spring L attached thereto and to the bracket D as shewn
in section at Figs. 2 and 3.
From the above described arrangement it will be seen that on a current
passing through A, the wires H H will be drawn in opposite directions across
the bar A, and will thereby effect a corresponding rotation of the axis C in the
direction of the arrow.
Owing to the resistance of the spring L such rotation will be proportionate
te the strength of the current and consequently the pointer E in being moved
to a corresponding extent over the ampere scale, will indicate the strength of
the current passing through A. If the current to be measured is weak, the action
thereof on the wires H H may be increased by making the bar A of a looped
form such as that indicated at Fig. 8, so that each limb of the fork is subjected
on both sides to the action of the current.
It will be readily understood that the arrangement of the wires and parts

page_text: connected thereto might be variously modified for operating an ampere index
in the manner described.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we
claim is:
1. An ammeter consisting of a flat conductor through which the current to
be measured is passed, and transversely across which extend suitably supported
iron wires that are so connected to a spindle carrying an index moving over an
ampere scale that on a current passing through the conductor the said wires
in being drawn across the latter are made to turn the spindle and index in
opposition to a spring substantially as described.
2. In an ammeter, the combination with a flat conductor A through which
the current to be measured is passed, of wires H H extending partly across the
conductor and suitably supported at one end while the other end is pivottally
connected to an arm F on the spindle C carrying a balanced index E moving
over an ampere scale, the rotation of the spindle C being resisted by a spring,
substantially as described.
3. An ampere meter combined and operating as herein described with reference
to the drawings.
Dated this 28th day of August 1897.
ABEL & IMRAY,
Agents for the Applicants.