ELECTRIC METER
Year: 1884

page_text: "
I, JOHN SMITH RAWORTH of No 24 Brazenose Street, Manchester, in the county
of Lancaster, Electrical Engineer, do hereby declare the nature of my invention for
ELECTRIC METER" to be as follows:-
-
My invention relates to an electric meter which is constructed as follows:--An
iron spindle, capable of turning freely on pivots or bearings, has coiled around it
but not touching it an insulated wire, and from its ends iron arms project. When
the spindle is arranged vertically the following is one method of constructing the
instrument.
The wire is-led to the upper end of the spindle, parallel to and under the upper
arm, is coiled around the spindle, passes under and parallel to the lower arm, ascends
vertically and returns above and parallel to the upper arm. The spindle has
attached to it an adjustable torsion spring, and it may be provided with suspending
fibres to relieve its pivot of a part or the whole of its weight; it is also provided
with a pointer arranged to move along a graduated scale. When a current of
electricity passes through the wire, the spindle is magnetised by the action of the
coil, the arms forming polar extensions. As the current passes also along the wires
running parallel to the arms, the latter are more or less deflected, both in the same
angular direction, causing the spindle to turn partly round and its pointer to
indicate on the scale the extent of the deflection. The wires and coil may be
either of small or of great resistance, and conduct the whole or part of the current
according to the purpose for which the meter is employed; for instance, whether
to measure current or electromotive force.
The torsion spring may be fastened to a moveable head, so that its turning action
on the spindle may be varied in such a manner as to bring back the moveable
pointer to zero. In this case, the torsion head is provided with a finger which
indicates on the scale the deflection of the spring required to bring the pointer to
zero.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.

page_text: 1, JOHN SMITH RAWORTH of No 24 Brazenose Street, Manchester, in the County
of Lancaster, Electrical Engineer, do hereby declare the nature of my invention for
"ELECTRIC METER" and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
"
My invention relates to an electric meter, that is to say, an instrument for
measuring the electric current in a circuit, in which case it may be termed an
electro-dynamometer," or with suitable modifications, for measuring the electro-
motive force, in which case it may be called a "volt-meter." For both purposes,
the principles of action are the same, but the construction is so far modified as to
suit two different conditions, the chief modification being in the character of the
coils employed; in the one case, for the electro-dynamometer, a coil conductor of
large sectional area and very low resistance is used; in the other case, for the
volt-meter, coils of fine wire and very high resistance are used. I will describe
both forms referring to the accompanying drawings in the several figures of which
the same reference letters are, as much as possible, employed to indicate corre-
sponding parts.
Fig. I is a vertical section and Fig. 2 is a sectional plan of an electro-dynamometer
according to my invention, Fig. 3 being a front view shewing parts immediately
behind the dial part of which is supposed to be removed. Fig. 4 is a vertical
section and Fig. 5 a sectional plan of the modified form of the instrument
constituting a volt-meter, Fig. 6 being a transverse section.
A is an iron spindle delicately pivotted at its ends where there are two iron
arms a a projecting from it in opposite directions. Around the spindle A. there are
conducting coils B consisting, for the electro-dynamometer, as shewn in Figs. 1
and 2, of a few convolutions of copper bar of rectangular section helically wound
without contact with each other, but in the volt-meter, as shewn in Figs. 4 and 5,
consisting of numerous convolutions of fine insulated wire. In either case, when
these coils are acted on by electricity, the spindle A becomes polarised, its arms a a
constituting polar extensions of the magnet into which it is converted.
As shewn in Fig. 1, the electric current entering by the post C passes along a
metallic framing C¹ C² C³ through the coil B and out by the post D or in the
reverse direction. In passing along the parts of its circuit C¹ and C³, which are
parallel to the arms a a, it tends to deflect them and so to turn the spindle A partly
round, with more or less force according as the current is greater or less. As shewn
in Figs. 4, 5 and 6, the electric current entering by the post C passes through a
number of convolutions of fine insulated wire C1 C2 C3 C' wound round a rectangular
casing E outside the spindle A and its coil B. In this case also the current in the
parts C¹ and C³ of the rectangular coil is parallel to the arms a a and tends to
deflect them the more, the greater the electromotive force.
At the front end of the spindle A is fixed a light index wire F, which may be of
aluminium. It is counterbalanced by an adjustable weight F1 and is bent forward
so as to project through a hole in a dial G. Through this dial passes a central
spindle H which can be turned by hand and which has fixed to its inner end the

page_text: innermost convolution of a volute spring K, the outermost convolution of which is
connected by an arm k to the index wire F. On the spindle H, outside the dial G
and protected by a glass L, there is fixed an index M pointing to graduations on
the dial. When the instrument is put in circuit, the spindle H is turned by hand-
until the force of the volute spring K is made to balance the force tending to turn
the spindle A by deflecting the arms a a, as can be seen by observing the point of
the wire F just vibrating within the hole of the dial through which it passes.
The index M will then point to a graduation on the dial G by which can be
ascertained the number of ampères in the current acting on the electro-dynamo-
meter, or the number of volts in that acting on the volt-meter. As shewn in Figs. 4
and 6 a key N pressed upwards by a spring can be used to put the volt-meter in
circuit, by pressing down this key by the finger and thereby bringing into contact
two metallic springs n n, by which the circuit of the instrument is closed.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
The construction of electric meter, wherein a spindle surrounded by a coil in the
circuit, the electricity of which is to be measured, and having arms parallel to parts
of that circuit, is at the same time polarised by the coils, and urged by the action
on its arms to turn in opposition to a spring adjustable to the current or to the
electro-motive force in the circuit, substantially as herein described.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.