IMPROVEMENTS IN APPARATUS FOR MEASURING THE STRENGTH OF ELECTRIC CURRENTS
Year: 1883

page_text: LETTERS PATENT to Frederick Vilhelm Andersen of Stainsby Road, Poplar,
.
in the County of Middlesex for an Invention of "IMPROVEMENTS IN
APPARATUS FOR MEASURING THE STRENGTH OF ELECTRIC CURRENTS
PROVISIONAL SPECIFICATION left by the said Frederick Vilhelm Andersen
at the Office of the Commissioners of Patents on the 4th May 1883.
FREDERICK VILHELM ANDERSEN of Stainsby Road Poplar in the County of
Middlesex "IMPROVEMENTS IN APPARATUS FOR MEASURING THE STRENGTH OF
ELECTRIC CURRENTS
"
The apparatus constructed according to my Invention consists of a needle made
of soft iron a straight flat steel spring and three or more coils of copper wire
through which the current passes. The needle is rigidly connected to a small brass
tube which passes through the centre of the needle at right angles to its greatest
length. The aforesaid spring passes down through this tube its lower end being
fastened to the lower end of the tube and its upper end being held rigidly by a
fixed support passing into a slot in the upper end of the said tube-The upper
and lower extremities of the tube are provided with small pivots which work in
jewelled bearings the weight of the tube and of the needle which is attached to it
being sustained by the above mentioned spring. The needle is thus free to oscillate
through a considerable angle the amount of such oscillation being regulated by
the torsion of the spring by which the needle is suspended. The coils of wire are
placed with their axes in the plane of oscillation of the needle in such a manner
that their axes forming radii of a circle of which the needle is the centre that a
current of electricity passing through them will tend to deflect the needle, the
amount of such deflection being proportional to the strength of the current and
the torsion of the spring which when there is no current passing maintains the
needle at a fixed point corresponding to zero upon the scale. A light pointer is
attached to the tube upon which the needle is fastened and this pointer indicates
the deflections of the needle upon a graduated scale in front of the instrument.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Frederick Vilhelm Andersen in the Great Seal Patent Office on
the 1st November 1883.
FREDERICK VILHELM ANDERSEN of Stainsby Road Poplar in the County of
Middlesex
"IMPROVEMENTS IN APPARATUS FOR MEASURING THE STRENGTH OF
ELECTRIC CURRENTS
"1
This Invention has for its object to produce an instrument which will indicate
in absolute measure the strength of the current which is passing through it at any
given moment When constructed with a much higher internal resistance it "can
be used to indicate in absolute measure the electromotive force between any two
points of a circuit to which it is connected as a shunt
It is well known that when an electric current passes through a helix of wire
a piece of soft iron placed in the vicinity thereof becomes a temporary magnet or
electro magnet and, is attracted towards the centre of the helix and, that if a
magnetised needle be placed in the neighbourhood of the said helix the said needle
is deflected one end being attracted and the other end-repelled.
The apparatus constructed according to my Invention has for its essential features
a needle of soft iron (or its equivalent) magnetized and deflected by the electric
current to be measured a spring put in torsion by the said needle and three or more
coils of copper wire through which the current passes
1/1
And in Order that my, said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheets of drawing the same letters of reference
indicating corresponding parts in all the corresponding figures
1.
I will first describe with reference to figures 1 and 2 an instrument with three
coils Figure 1 being a vertical section and Figure 2 a horizontal section-The
needle A is of soft iron and is rigidly connected to a small brass tube B which
passes through the centre of the needle A at right angles to its greatest length-
The spring C passes down through this tube its lower end being fastened to the
lower end of the said tube and its upper end being held rigidly by a fixed support D
passing into a slot in the upper end of the said tube B. The upper and lower
extremities of the said tube B are provided with small pivots. which..work
in jewelled bearings E carried by the bracket piece H the weight of the tube
and of the needle which is attached to it being sustained by the spring .C
so as to relieve the lower pivot of weight-The needle A is thus free.to:
oscillate through a considerable angle the amount of such oscillation being
regulated by the torsion of the spring C.-The coils of wire J1 J2 J3 are con-
nected together in series and placed with their axes in the plane of oscillation of
the needle in such a manner that their axes form radii of a circle of which. the.
needle is the centre (as shewn clearly in figure 2) and a current. of electricity
passing through them will tend to deflect the needle A. the amount of such deflection
being proportional to the strength of the current and the torsion of the spring C,
which when there is no current passing maintains the needle. at. a fixed point
corresponding to zero upon the scale. A light pointer F is attached to the tube B:
and this pointer indicates the deflections of the needle upon a graduated. Scale G
situated in front of the instrument and protected. by a glass K.-The position:
shewn in the Drawings is the position of rest, the needle. lying in or nearly in the
common axial line of the two opposite coils J2 J3 or it may lie within an angle of
thirty degrees to that line. The angle varying with the shape and size of the coils
and the distance between them and the needle. I, I, are the binding screws to
which the wires are secured so as to join up the coils with the circuit as shewn by
55

page_text: the detail section Figure 1. When a current of Electricity passes through the
coils, the coils J* J' magnetize the needle A, whilst the coil J' attracts one end and
repels the other of the said needle, thus causing it to turn upon its centre or deflect,
The influence of the coils J2 J3 and the torsion of the spring Care opposed to this
deflection and the position finally taken up by. the needle A, and indicated
by the pointer F upon the Scale G is a measure of the current.-When the current
through the coils ceases, the spring C, brings the needle A and consequently the
pointer F back to the original position indicating Zero. This arrangement has
great advantages; the pivots relieve the spring from shocks in transit and all the
moveable parts of the apparatus being suspended by the spring, injurious friction
is prevented and if the parts be properly balanced there is no necessity to level it
upon its base-I do not limit myself to the use of three coils, as more than three
may be used. Figure 3 is a transverse Section and Figure 4 is a plan with the
case in Section shewing an arrangement wherein four coils are used-Although the
appearance of this instrument is somewhat different from that shewn in figures 1
and 2, the essential features are the same.-The coils. Ji being of one turn only
are shewn as being made of horse-shoe shaped copper bars insulated from each
other and from the bottom plate to which they are fixed:--They are connected at
the ends in series after the manner of the arrangement first described.
pointer is here shewn situated above the coils so that the scale is at the top of the
instrument. I have marked the parts in this arrangement which correspond with
those shewn in the first arrangement with like letters of reference so that the said
arrangement, figures 3 and 4 will be readily understood from the preceding
description of the arrangement, figures 1 and 2.
The
I do not limit myself to the precise details shewn in the drawings as they may
be varied without departing from the nature of my Invention, for example I may
make the needle in the form of a soft iron tube of an oblong or oval form in cross-
Section, this tube taking the place of that marked B in the drawings, the support
of the said tube as in the arrangements shewn being fixed to the stand indepen-
dently of the coils through which the current passes-Or the needle may be formed
by a brass tube of an oblong or oval form in cross-Section coiled with soft iron wire
when it is desired to use the instrument as a voltmeter or Instrument for measuring
Electro-motive force, the coils are wound with many turns of fine wire, so as to
give a very high resistance.
I may wind the same instrument with two sets of coils, one set having a high
resistance and the other a low resistance, each set being provided with its own
binding screws in order that the same instrument may be used either as a voltmeter
or as an arınmeter.-In instruments constructed according to my Invention, there
are no permanent magnets which cause great uncertainty by the deterioration in
strength to which they are liable-The deflections of the needle, as indicated by
the pointer on the scale can, it will be evident by giving a proper form or arrange-
ment to the needle, be made directly proportional to the strength of the current,
thus indicating in amperes directly upon the Scale and entirely obviating the
necessity for any calculation.
Having now described and particularly ascertained the nature of my said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is :-
First, The herein before described apparatus for measuring the strength of
electric currents, the essential feature of the said apparatus being the combination
of three or more coils through which the electric current passes, a needle or its
equivalent magnetized and deflected by the Electric current and a spring put in
torsion by the movement of the said needle, all being arranged and operating to
give indication of the strength of the electric current substantially as hereinbefore
described.

page_text: Second, In apparatus for measuring the strength of electric currents, the combi-
nation of coils through which the current passes, a needle (or its equivalent) and a
spring enclosed with a pivotted protecting tube, all being arranged and operating
to give indication of the strength of the Electric current substantially as herein-
before described.
Third, In apparatus for measuring the strength of Electric currents, the employ-
ment of a tube and a spring carried by the said tube and a support so that when
the tube or the needle carried by it is acted upon by an electric current the
Spring is put in torsion substantially as and for the purpose hereinbefore described.
Fourth, The arrangement and combination of parts constituting the apparatus
for measuring the strength of Electric currents as hereinbefore described and
illustrated in figures 1 and 2 of the accompanying Drawings.
Fifth, The arrangement and combination of parts constituting the apparatus for
measuring the strength of Electric currents as herein before described and illustrated
in figures 3 and 4 of the accompanying Drawings.
In witness whereof I the said Frederick Vilhelm Andersen have to this my
Specification set my hand and Seal this twenty-fifth day of October One thousand
eight hundred and eighty three.