Improvements in or relating to Galvanometers.
Year: 1895

page_text: Date of Application, 18th Jan., 1895
Complete Specification Left, 18th Oct., 1895-Accepted, 28th Dec., 1895
PROVISIONAL SPECIFICATION.
Improvements in or relating to Galvanometers.
I, CARL LUDWIG RUDOLPH ERNEST MENGES, of 82/84 Balistraat, The
Hague, in the Kingdom of Holland, Electrician, do hereby declare the nature of
this invention to be as follows:-
My invention relates to self-controllable electro-magnetic galvanometers, that
is to say to galvanometers that do not require any separate instrument for
controlling them, and especially to those intended to be used as volt-meters or
ammeters.
According to my invention the magnetic field in the apparatus is controlled by
means of the attraction of one part of the magnetic circuit upon another part, in
combination with suitable means for varying the magnetic flux.
If the magnetic field in such a construction changes, then, with the aid of the
said controlling apparatus, the field can be re-adjusted to its original strength, so
that the deflections of an indicating pointer produced by given electric currents
will be the same as when the apparatus was originally graduated.
My invention may be applied to various systems of electro-magnetic galvano-
meters and can be performed chiefly in the three following methods; firstly, a
method by which the controlling apparatus itself acts also as a current meter;
secondly, a method in which the controlling apparatus conducts the magnetic flux
directly to the movable part of the current meter and thirdly, one in which the
controlling apparatus forms a separate part of the magnetic circuit between the
magnet and the current meter proper.
These three methods are illustrated by the accompanying drawing, in which
Figure 1 is a front elevation and
Figure 2 is a plan of an improved form of galvanometer embodying my invention,
the fixed magnet and soft iron "keeper" being removed.
Figures 3 and 4 are front elevations of galvanometers illustrating the application
of my invention to existing types of galvanometers.
Like letters denote corresponding parts throughout the drawing.
Referring now to Figure 1, which shows an improved form of galvanometer or
current meter illustrating, by way of example, my first method of controlling such
instruments, viz. a method by which the controlling apparatus itself acts also as a
current meter, N m S is a magnet, N' and S' are the pole pieces attached thereto.
Between the pole pieces NT and S' is a movable device consisting of pole
projections nnn and ss, the two parts nnn and ss being carried by the upper
and lower ends respectively of a rod or spindle A of non-magnetic material. The
device n As is pivotted at its lower end in a cylindrical opening S* in the pole
piece S and at its upper end in a conical orifice N* in the pole-piece N¹. 'On
account of the conical shape of the upper part of the device n As the magnet
exerts au upward magnetic attraction thereon. The movable device n As will
therefore be either lifted against the upper conical bearing N or will rest in the
lower bearing S according to whether the upward magnetic attraction or the force
of gravity is the greater.
The bearings N and S* in the pole pieces are so arranged that the movable
device n As has a little "play" in an axial direction.
The device n A s may be moved up and down when desired, by a suitable hand

page_text: contrivance such for example, as is illustrated in Figure 1, in which B is a rod
adapted to move in the block C and carrying at its upper end a spring finger D.
The said spring finger is adapted to engage at its two extreme positions with the
upper and lower faces of the annular groove A' in the rod A. A spiral spring E
which surrounds the rod B between the finger D and the block C, serves to keep
the said finger D normally out of contact with and midway between the two faces
of the groove A', and thus the rotary movement of the device n As is not
impeded. A knob or button B' is provided on the rod B preferably outside the
case F of the instrument by means of which the vertical movement may be imparted
to the movable device n As when desired.
The lower part of the pole projection n n n is of a semi-circular or half ring
shape as shown in Figure 2, and is arranged to move in a wire coil or solenoid G.
This coil is not shown in Figure 1 but the dotted arrow indicates the direction
in which the current should pass round the part n. A spiral spring H around
the spindle A furnishes a counteracting force against the turning action of the
solenoid G on the lower semi-circular part of the pole projection nnn.
resulting deflection due to the turning of the device n A s by the action of
the solenoid G may be indicated by means of a fixed pointer (not shown) in
connection with a movable cylindrical scale I which latter is carried by an arm A²
attached to the rod or spindle A.
The
A soft-iron armature or "keeper" J is provided the poles of which can be
brought nearer to or moved away from the fixed pole-pieces N' S' of the
instrument by means of the adjusting screw K.
Now if we disregard that part of the magnetic flux of the magnet N m S which
s lost by leakage, then one part of the total magnetic lines passes through the
"keeper", and the remaining part passes through the fixed pole pieces N¹S¹ and
the movable pole projections n nn and ss. By shifting the position of the
"keeper" J we may obtain just sufficient flux through the movable device n As
to furnish an upward magnetic attraction equal to the downward force of gravity
acting on the device n As and thus maintain the said device floating in the
"field." If now the device n As be moved by the finger D on the rod B up or
down in its bearings it will remain stationary equally well in either of its extreme
positions or in fact in any intermediate position. If the instrument be now
calibrated, with respect to the deflections produced by various strengths of current,
the instrument will again indicate correctly if, after some alterations in the
magnetic field, the magnetic state of the movable device n As is restored to its
original value by suitably shifting the "keeper" or armature J.
The magnetic leakage cannot have a detrimental effect, because it depends only
on the shape or configuration of the parts, which remains practically the same,
and also on the magnetic state which, when altered, is again restored to the
original state in the main parts of the instrument by shifting the "keeper” J.
"
Some variable magnetic leakage may occur between the poles of the "keeper'
and the fixed pole pieces N' S¹ but these points of leakage are so far away from the
movable device as to have no detrimental effect.
I may also apply my improvements to existing types of galvanometers, such for
example as a Deprez or Ayrton & Perry ammeter in which the current meter
proper consists of a movable needle n s placed between coils G G (Figure 3) the
magnetic flux from an adjustable magnet N m S being conveyed to the needle n s
by means of the extended pole pieces N₁ and S¹ S³.
In applying my improvements to such an instrument, as shown in Figure 3,
I divide the magnetic circuit by forming one of the pole pieces in two parts S¹
and S2 and I make the part S2 adjustable to act as a controlling device for the
instrument. For this purpose the said controlling piece S2 is pivotted at L at the
end nearest the needle ns, while its opposite end is capable of being lifted by
the attraction of the adjacent part S₁ of the pole piece and is provided thereon
with a counterpoise weight 0.
By shifting the counterpoise O the controlling attraction may be adjusted so

page_text: that, with a corresponding magnetic flux, a predetermined deflection of the needle
is obtained for a given strength of current.
A suitable arrangement may be employed for moving the controlling piece S² up
and down, to control the attraction of the magnet as herein before explained,
similar to that described with reference to Figure 1. The two pins P P in this
case serve as projections for the finger to engage with.
The necessary changes in the magnetic flux are obtained by varying the distance
between the adjustable maguet N m S and the fixed portions of the pole pieces N¹
and S¹ by means of the adjusting screw K.
In the instrument shown in Figure 4 which illustrates my third method of
controlling, the magnetic lines from the magnet N m S pass through the divided
pole projections S' S³ to the pole face S³ and thence to N₁ by way of the
cylindrical core Q which is fixed midway between the pole faces N₁ and S³.
Around the core Q a wire coil G is adapted to swing in the manner of the well-
known d'Arsonval galvanometer.
The part S is adapted to slide within S³ so as to be easily movable in a vertical
direction. A counterpoise weight O acts against the attraction of the pole S' on
the movable part S².
The controlling movement of the part S² is obtained by means of the spring D
operated by the handle B'.
The required changes in the magnetic flux are obtained by approaching or
receding a soft iron armature or "keeper" J.
The movement of the movable pole piece S may be indicated on an enlarged
scale by means of a long pointer R. A glance at the instrument then suffices to
see whether the magnetic attraction is still sufficient to maintain the movable
piece S lifted against the force of gravity.
Such an index finger may obviously be applied to various other forms of
instrument.
In all the forms of apparatus I have described, by way of example, I have
indicated the application of the force of gravity for the controlling action but I may
obviously also employ the force of a spring.
I sometimes prefer to use electromagnets instead of the permanent magnets
herein before described.
Dated this 18th day of January 1895.
COMPLETE SPECIFICATION.
Improvements in or relating to Galvanometers..
I, CARL LUDWIG RUDOLPH ERNEST MENGES, of 82/84 Balistraat, The Hague,
in the Kingdom of Holland, Electrician, 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 :-
My invention relates to self-controllable electro-magnetic galvanometers, that is
to say, to galvanometers that do not require any separate instrument for controlling
them, and especially to galvanometers intended to be used as volt-meters or
aminelers.
According to my invention a galvanometer is provided wherein the magnetic
field is controlled by means of the attraction of one part of the magnetic circuit
upon another part, in combination with suitable means for varying the
magnetic flux.
If the magnetic field in such a construction changes, then, with the aid of the

page_text: said controlling apparatus, the field can be re-adjusted to its original strength, so
that the deflections of an indicating pointer produced by given electric corrents
will be the same as when the apparatus was orginally graduated.
My invention may be applied to various systems of electro-magnetic galvano-
meters and can be performed chiefly in the three following methods: firstly, a method
in which the controlling apparatus itself acts also as a current meter; secondly, a
method in which the controlling apparatus conducts the magnetic flux directly to
the movable part of the current meter; and thirdly, one in which the controlling
apparatus forms a separate part of the magnetic circuit between the magnet and
the current meter proper.
These three methods are illustrated by the drawing accompanying my Provisional
Specification, in which
Figure 1 is a front elevation, and
Figure 2 is a plan of an improved form of galvanometer embodying my invention,
the fixed magnet and soft iron "keeper" being removed.
Figures 3 and 4 are front elevations of galvanometers illustrating the application
of my invention to existing types of galvanometers.
Like letters denote corresponding parts throughout the drawing.
Referring now to Figure 1, which shows an improved form of galvanometer or
current meter illustrating, by way of example, my first method of controlling such
instruments, viz. a method in which the controlling apparatus itself acts also as a
current meter, N m S is a magnet to which are attached pole pieces N¹, S¹.
Between the said pole pieces is a movable device consisting of magnetisable pole
projections nnn and ss carried by the upper and lower ends respectively of a rod
or spindle A of non-magnetic material. The device n As is pivotted at its lower
end in a cylindrical recess S* in the pole piece S₁ and at its upper end which is
conical in a conical recess N* in the pole-piece N¹. The bearings N* and S* in
the pole pieces are so arranged that the device n As has a small amount of "play
in an axial direction. On account of the conical shape of the upper part of the
device n As the magnet exerts an upward attraction thereon, and if such attraction
is greater than the weight of the said device the latter will be lifted against the
conical recess N*.
"3
The device n As may be moved up and down when desired, by a suitable hand
contrivance comprising a rod B adapted to move in a guide block C secured to the
pole piece S and carrying at its upper end a spring finger D adapted to engage at
its two extreme positions with the upper and lower faces of an annular groove A¹
formed by two collars on the rod A. A spiral spring E which surrounds the rod B
between the finger D and the block C, serves to keep the said finger D normally
out of contact with and midway between the two faces of the groove A', and thus
the rotary movement of the device n As is not impeded. A knob or button B¹
is provided on the rod B preferably outside the case F of the instrument by means
of which an axial movement may be imparted to the movable device n As
when desired.
A
The lower part of the pole projection nnn is of a semi-circular or half ring
shape as shown in Figure 2, and is arranged to move in a wire coil or solenoid G.
This coil is not shown in Figure 1 but the dotted arrow indicates the direction in
which the current should pass round the curved part of the pole projection n.
spiral spring H surrounding the spindle A and connected thereto at one end and
bearing against a fixed abutment finger H' at the other end furnishes a force which
tends to counteract the turning action of the solenoid G on the lower semi-circular
part of the pole projection.nnn. The resulting deflection due to the turning of
the device n As by the action of the solenoid G may be indicated by means of a
fixed pointer (not shown) in connection with a movable cylindrical scale 1. which
latter is carried by an arm. A attached to the rod or. spindle A.
Jis a soft-iron armature or “ keeper" movable in guides by means of a screw K
whereby its poles can be caused to approach or to recede from the fixed pole
pieces N' S. The said armature acts as a magnetic shunt to the magnetic lines.

page_text: Now disregarding that part of the magnetic flux of the magnet N m S which is
lost by leakage, all of the magnetic lines that do not pass through the "keeper" J,
pass through the fixed pole pieces N'S' and the movable pole projections nnn
and ss.
By shifting the position of the "keeper" J we may obtain just sufficient
flux through the movable device n As to furnish an upward magnetic attraction
equal to the weight of the device n As and thus maintain the said device floating
in the field."
The equilibrium however is unstable, therefore if the device n As be moved by
the finger D on the rod B up or down in its bearings, it will, when it passes a
certain intermediate position, jump over to the other extreme position, showing
thereby that there is exact equilibrium in that intermediate position.
"
If the instrument be now calibrated, with respect to the deflections produced by
various strengths of current, the instrument will again indicate correctly if, after
some alterations in the magnetic field, the magnetic state of the movable device n As
is restored to its original value by suitably shifting the " keeper or armature J.
The magnetic leakage cannot have a detrimental effect, since it depends on the shape
or configuration of the parts, which remains practically the same, and on the
magnetic state which, when altered, is again restored to the original state in the
main parts of the instrument by shifting the "keeper” J.
"
Some variable magnetic leakage may occur between the poles of the "keeper
and the fixed pole pieces N' S₁ but these points of leakage are so far away from
the movable device as to have no detrimental effect.
I may apply my improvements to existing types of galvanometers, such for
example as a Deprez or Ayrton and Perry ammeter in which the current meter
proper consists of a movable needle ns placed between coils G G (Figure 3) the
magnetic flux from an adjustable magnet N m S being conveyed to the needle ns
by means of the extended pole pieces N' and S¹, S.
In applying my improvements to such an instrument, I divide the magnetic
circuit by forming one of the pole pieces in two parts S1 and S2 and 1 make the
part Sadjustable to act as a controlling device for the instrument. For this
purpose the said controlling piece S2 is pivotted at L at the end nearest the
needle ns, while its opposite end is capable of being lifted by the attraction of the
adjacent part S' of the pole piece and is provided with an adjustable counterpoise.
weight O.
By shifting the counterpoise O, the parts S2 may be so adjusted that a
predetermined deflection of the needle may be obtained for a given strength
of current.
A suitable arrangement may be employed for moving the controlling piece S² up
and down, to control the attraction of the maguet as herein before explained, similar
to that described with reference to Figure 1. The two pins P P in this case serve
as projections for the spring finger to engage with.
The necessary changes in the magnetic flux are obtained by varying the distance-
between the adjustable magnet Nm S and the fixed portions of the pole pieces N¹
and S by means of the adjusting screw K.
In the instrument shown in Figure 4 which illustrates my third method, the
magnetic lines from the magnet N m S pass through the divided pole projections S¹ S
to a pole piece S8 and thence to the pole piece N by way of the cylindrical core Q
which is fixed midway between the faces of the pole pieces N' and S³.
the core Q a wire coil G is adapted to swing as in the well-known d'Arsonval
galvanometer.
Around
The part S2 is adapted to slide within the pole piece S³ so as to be easily movable
in a vertical direction. A counterpoise weight O acts against the attraction of the
pole S on the movable part S³.
The movement of the part S2 is effected by means of the spring finger D operated.
by the bandle B¹.
The required changes in the magnetic flux are obtained by causing a soft iron.
armature or keeper J to approach or recede from the pole pieces N¹, S¹.
66
:

page_text: The movement of the movable pole piece S may be indicated on an enlarged
scale by means of a long pivotted pointer R. A glance at the instrument then
suffices to see whether the magnetic attraction is still sufficient to maintain the
movable piece S2 lifted against the force of gravity.
Such an index finger may obviously be applied to various other forms of
instrument.
I may also apply the constant magnetic field obtained in the manner hereinbefore
described, for calibrating or checking the constants of ballistic galvanometers.
For instance an apparatus may be used the main features of which are similar to
that described with reference to Figure 4. If the terminals of that instrument
are connected with the ballistic galvanometer, and the coil G is swung round
through a definite angle (by hand or by the action of a spring for instance) then a
current will be generated therein, which may be used in the well-known manner for
calibrating or checking the constants of the ballistic galvanometer. The only
difference in construction I prefer to make, is that I construct the coil G somewhat
larger and more substantial.
For the same purpose I may also use other forms of magnetic fields, for example,
a ring-shaped field, one pole piece being cylindrical and surrounded by the other
pole piece. In that case I use a cylindrical coil which I let drop through the field
as in Hibbert's instrument.
In all the forms of apparatus I have described, by way of example, I have
utilised gravity as the controlling force but I may obviously also employ a spring
for this purpose.
I sometimes prefer to use electromagnets instead of the permanent magnets
herein before described.
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. An electromagnetic galvanometer in which the magnetic flux required for its
action is transmitted through a movable part of the magnetic circuit, which movable
part by the attraction to which it is subjected controls the magnetic flux, in
connection with a regulating device, acting as a magnetic shunt, or magnetic
resistance, substantially as described for the purpose of maintaining a constant
magnetic flux in the galvanometric field.
2. A galvanometric device consisting of two magnetisable parts connected by a
non-magnetic piece so as to form a movable device, each magnetic part being
magnetised at one end by a fixed magnet while the other end is deflected by the
current to be measured.
3. An apparatus consisting of a self-controllable and adjustable magnetic field
constructed substantially of the kind indicated in the first claiming clause; and a
wire coil which may be moved in that field, by means of a suitable external force,
for the purpose specified.
4. A galvanometer constructed substantially as described with reference to
Figures 1 and 2, or to Figure 3, or to Figure 4 and operating as specified.
Dated this 18th day of October 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.