Improvements in Apparatus for Measuring and Regulating Electric Currents.
Year: 1887

page_text: Date of Application, 2nd Dec., 1887
Specification Accepted, 13th Jan., 1888
COMPLETE SPECIFICATION.
Improvements in Apparatus for Measuring and Regulating Electric
Currents.
I ARTHUR WRIGHT of the Brighton Electric Light Company Limited, of Gloucester
Road Brighton, in the county of Sussex, Electrical Engineer, do hereby declare the
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 :-
:-
The object of this invention is to produce very sensitive apparatus by which a long
range of movement for a small amount of energy consumed therein may be obtained,
and which shall be suitable for measuring and also regulating when desired either
continuous or alternating currents, and be also compact and of convenient form and
dimensions. The present improvements are applicable to voltmeters, ammeters, and
Coulomb meters, also to regulating and controlling the current of Dynamos and like
machines.
"
The invention depends upon the known principle of the expansion of a fine wire or
other metallic conductor when traversed by an electric current, as in the "Cardew
voltmeter, but when such a short conductor is stretched horizontally or nearly so, its
sag or deflection from normal position on passage of a current is too minute to be
practically or conveniently utilized for metrical purposes.
This invention consists in so arranging a series of metallic conductors of short
lengths and the parts connected therewith that a long range of motion due to
expansion of the series when traversed by a current is obtained, and also in summing
up mechanically and indicating or recording the amounts of the deflection or sag of
each separate conductor or set of conductors, and also in a method for regulating or
altering for any purpose the current of a dynamo or like machine. The principle of
the invention is diagrammatically illustrated in figure 1 of the annexed drawings
wherein bp, fl, represent two of a series (which may contain any suitable number)
of light insulating bars suspended and surrounded by a fine wire or conductor fixed
at any point a connected to the main circuit, and passing round one end of the
bar bp through an insulating block at c, g round the end of a bar fl to a point h,
and returing in the same way, or as hereinafter set forth, to a like fixed point k. At
the point hat or about the centre of the lowest loop of the series, a connection is
made to a spring or other opposing constant force q tending to keep the conductors
stretched tight, and which may be connected to a spring indicator or other mechanical
device such as hereafter indicated.

page_text: By this arrangement it is evident that the movement of cg, will be equal to the
expansion or sag of the conductors supporting the upper bar bp, and the range of
motion of the point will equal that plus the expansion or sag of the conductors
supporting the next bar fl; and by employing a sufficient number of such bars and
lengths of conductor forming separate loops whose individual expansions or increases
of sag are added together, any desired range of motion of the point h may
be obtained.
I will now further describe my improvements in reference to Figures 2-3 of
accompanying drawings which represent a voltmeter or ammeter and a Coulomb meter
embodying my improvements, though it is to be understood that these illustrate only
the principle and certain arrangements of my invention and I do confine myself to
these particular forms only.
I pass the current to be measured through a fine wire a, b, c, d, e, f, h, l, m, n, g, p, k,
whose two ends a, and k are connected to the hooks a¹ and k' the said hooks being
connected to the terminals x, y of the instrument.
From the hook at a¹ the wire is stretched round a series of very light insulating
bars b, p, d, n, f, as above described and led back to the other terminal k¹. The
centre of the lowest span f, h, l, is connected to a spring or other opposing constant
force which keeps the wire spans stretched and on passage of a current the aggregate
expansion in all the loops a, b, c, p, k; c, d, e, n, g, etc. moves the arm h², r, so that
the distance a to h, is increased this being the sum of the sags a to
and e to h.
c, c to e,
In voltmeters and ammeters the end passes over a scale s properly divided as
indicated in fig. 2 and the divisions show the pressure in volts or current passing in
amperes, and in Coulomb meters the end, has an integrating wheel or other
mechanism of suitable description attached thereto which will sum up the variations
of the passing current; such mechanism may consist of an integrating wheel t and
counter moving to and from the centre of an uniformly moving disc u, driven by
a clockwork, or other constant force, with which the integrating wheel is geared.
Instead of arranging conductors in the manner above described I sometimes wind
them as shown in figure 3 wherein a conductor is passed from a to b, then right over
to n, then to f, then through h, to 1, n, p, and k, taking care to insulate the wires
from one another at places like c, g, and e m where they will cross.
I prefer placing the system of loops horizontally and in a closed box, so that the
heat of one span may not interfere with that of an adjacent one. In regulators 1
make the arm h¹r introduce more or less resistance in the field or shunt on the same
of the dynamo whose current it is desired to regulate or alter, or I may make it act
as a relay to a variable resistance apparatus for effecting the same objects.
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
(1.) The hereinbefore described improvements in apparatus for measuring electrical
currents, consisting in the method of arranging and disposing a series of conductors
so as to obtain a long range of motion for a point in the series, by the summation
of the movements due to expansion or sag of such conductors when heated, which
motion may be applied substantially as and for the purposes set forth.
(2.) In apparatus for regulating electrical currents the combination of the herein-
before described method of obtaining a long range of motion with the means of
regulating by introducing a resistance substantially as and for the purposes set forth.
Dated this 1st day of December 1887.
By J. C. CHAPMAN,
70, Chancery Lane, London, W.C.,
Patent Agent.