Magnetic and Electric Measuring Instruments.
Year: 1897

page_text: PROVISIONAL SPECIFICATION,
Magnetic and Electric Measuring Instruments.
I, JAMES RUSSELL, Bridge Park, Selkirk, North Britain, Gentleman, do hereby
declare the nature of my invention to be as follows:-
This invention relates to instruments for the measurement of the magnetic
properties of iron, steel and other magnetic metals or materials, and they may
also be employed for measuring electric currents. My instruments for these
purposes of which there will be three or more modifications described and
which I shall call respectively A, B, C, etc., instruments depend upon the
shielding properties of a tube or rectangle (to be hereinafter defined) of iron, etc,
and I construct them in the following manner. Let coils of insulated wire be
constructed by preference two and of approximately rectangular or circular
shape and of any suitable proportions-and if two coils be used, let them be
formed into a rigid system in such a way that one side or portion of each coil
is near to one side or portion of the other coil. The wires of these sides or
portions of the coils will form the central wires and will be approximately
parallel if rectangular coils are used. These coils I shall call the internal coil
or coils of the instrument. The coils may consist of one, few, or many turns
of the insulated' wire and must be connected in series in such a way that a uni-
directional electric current flowing through them will be in the same direction
in the central wires of the coils and consequently in the opposite direction in
all the external wires. The central wires will be called the central or shielded
wires and the external wires will be called the external or unshielded wires.
Let the central wires be surrounded by a tube or rectangle of iron or other
magnetic metal the magnetic properties of which are to be measured or deter-
mined. I wish it to be understood that by the words "tube or rectangle" I
mean not only a hollow structure of circular or approximately circular
section or rectangular section, but of any other section which may
be found most suitable. It may be of any suitable length or it
may be very short approximately to or in fact being a ring
rectangle or other shape composed even of a single turn of wire of iron or other
magnetic metal or of any number of turns. I also include in my use of the
words "tube or rectangle "all or any of the above structures which may have
been slit approximately lengthways or parallel to their axis, or otherwise, in
one, two, or any number of places and the slit or slits may either be very narrow
or they may be of great relative width, so that in extreme cases one side or part
thereof or two sides or parts thereof of approximately rectangular structures may
be all that is left, or in the case of a circular or approximately circular section
one, two, or more ares may be all that is left. I also include any built up
structure, and that even when it consists only in part of the iron, etc., to be
examined; in fact I include any structure which exercises any effect however
slight in shielding the external field-to be afterwards mentioned from the
central or shielded wires. The tube or rectangle and internal coils must be of
suitable relative dimensions, so that they shall have entire freedom of motion
or

page_text: the one relative to the other, within the rather narrow limits which the nature
of this combined apparatus imposes upon their relative motions. This com-
bined arrangement of internal coils and tube or rectangle I place in a uniform
magnetic field or, a field. approximating thereto and which magnetic field I
shall call the external field-in such a way that the shielded and unshielded
wires of the internal coils shall be at right angles-(or as nearly as possible) to
the lines of force of this external field. For the production of this external
field I use one, two, or more solenoids, which I shall call the external solenoid
or solenoids of suitable dimensions and suitably placed and adjustable relative
both to each other and the apparatus already described. The internal coils
and the external solenoids may be in series; or they may be excited by inde-
pendent electric currents. If now the internal coils be fixed relative to the
external field (or external solenoids) the tube or rectangle will move or tend
to move at right angles both to the lines of force of the external field and to its
own length (this being the same as the length of the shielded wires). On the
other hand if the tube or rectangle be fixed relative to the external field (or
external solenoids) the internal coils will move or tend to move at right angles
both to the lines of force of the external field and to the length of the shielded
(also unshielded external) wires. From the measurements of these forces, the
magnetic properties of the iron or other magnetic metal under test can be
determined, when the strength of the electric current is known, and, on the
other hand, the electric current may be measured when the magnetic properties
of the iron or other magnetic metal used, are known..
I mention that the force exerted by the tube or rectangle is equal and opposite
to the force exerted by the internal coil or coils and it may at the same time be
noted that this force is equal to the force exerted by the external unshielded
wires minus the force of the shielded wires. I may also find it necessary.
or convenient to measure the force of the unshielded wires plus the force of the
shielded wires and I may do this by measuring the force of rotation when at
least one (if more are used) of the internal coils is formed into a "couple." In
the event of my adopting one or a few turns of insulated wire for the internal
coil or coils, it would be necessary to have an additional coil or coils of many
turns in all respects similar to the internal coils only they would be fixed relative
both to the tube or rectangle and the external field. These fixed coils I shall
call the magnetising coils and they would also require to be so constructed,
that they would allow the necessary freedom of motion of the internal coils
already described. The magnetising coils might be wound directly on the tube
or rectangle or otherwise.
This arrangement of additional magnetising coils would preclude the use
of the tube or rectangle from being a movable part of the instrument, i.e., it
could not be attached to the balance beam or otherwise as an alternative. I
have described the use of solenoids for the production of the external field, but
it must not be understood to imply that I might not use either permanent sieel
magnet or electro-magnets, for the production of the external field. It must
also be understood that my use of the words "electric current " must not be held
to imply that I might not use alternating electric currents in any or all of the
instruments. The above description applies generally to all the instruments, and
in particular I wish to point out that the introduction of the magnetising coils
in conjunction with the internal coil or coils or otherwise (and that with or
without the additional motion forming a rotating "couple"-thus giving the
internal coil a double possible motion) may form and in all probability will
form an important modification or important modifications of any or all of the
instruments for the measurement of the magnetic properties of iron, &c., now to
bé described..
Instrument A. This instrument may weigh the force exerted by either the
tube or rectangle or the internal coils if either the tube or rectangle or the in-
ternal coils be fixed at one end of a balance beam, suitably and delicately hung;

page_text: or if the parts are duplicated, at both ends of the balance beam. If the internal
coils are fixed to the beam at one end, or in the case of the duplication of the
parts at both ends of the balance beam, I will adopt some method by which
the electric current can be introduced into the internal coils whether it be by
means of mercury connections, or by silver or other wires fixed and adjusted
in such a way that they might serve the double purpose of carrying the electric
current and delicately and suitably hanging the balance beam. Or this instru-
ment may measure the force by means of a torsion wire or other suitable fibre
and the usual torsion head arrangement. In either case from one or a series of
weighings or measurements of the forces, the magnetic properties of the iron etc.
can be determined.
Instrument B. This instrument is similar to instrument A only it is essen-
tial that the parts be duplicated and that one of the tubes or rectangles be a
standard tube or rectangle with which the tube or rectangle under test can be
compared. This instrument must be so connected up electrically that the forces
exerted on opposite sides of the beam, oppose each other. It is therefore a
difference of two forces that is weighed or measured, from which can be deter-
mined by one or a series of observations the magnetic properties of the iron etc.
under test.
Instrument C. One side of this instrument remains the same as in instru-
ment A in which either tube or rectangle or internal coils are fixed to one end
of the balance beam. On the other side of the beam however I fix a coil of
insulated wire of any suitable number of turns, while one or more stationary
but adjustable coils of insulated wire are placed, one above or below (if only one
stationary-adjustable-coil be used) or one above and the other below (if two
stationary-adjustable-coils be used). The planes of these coils will be approxi-
mately horizontal if the balance beam alternative be used, or approximately
perpendicular if the torsion wire alternative be adopted. I shall call these.
coils the balance coils. The internal coils and balance coils being connected
in series, I adjust, or approximate to such an adjustment the forces on the
opposite sides of the beam in such a way that the one would balance the other,
when the external field is supposed to be totally shielded from the central or
shielded wires. In this instrument therefore I measure the difference of two
opposing forces from which can be determined by one or a series of observations
the magnetic properties of the iron or other magnetic metal under test.
.
These instruments may also be employed for the measurement of the electric
current (amperes), electric pressure (volts), and electric power (Watts) and that
on an alternating current circuit, although not to the exclusion of the uni-
directional current. For this purpose I utilise the arrangements generally
and the principles involved in a tube or rectangle shielding the central wire
or wires from an external magnetic field which have already been described.
Instruments B and 0 are specially suited for magnetic measure-
ments. Instrument A, however, would measure the electric current
and the instrument could be designed to measure amperes, volts, or Watts
according to the known principles involved in the construction of these instru-
ments. My definition of the words "tube or rectangle" applies to these
instruments for measuring the electric current. The material used will in all
probability be soft iron. Great alterations are however made when necessary
in reducing the size and weight of the tube or rectangle, especially for delicate
instruments. The tube or rectangle may either be single or duplicated in which
case it may form a rotating or deflecting "couple." The internal coil or coils
may also consist of one, few, or many turns and I specify that the words "internal
coil" must not be held to imply that I might not use that part of a coil of a
single turn from which the external wire has been removed; in other words,
I distinctly specify that I may use a single wire, which however must correspond
to the central wire and must be shielded to a greater or less extent by the iron
ring or rectangle from the external field. The external solenoid or solenoids

page_text: may also consist of one, few, or many turns of insulated wire and it may also
consist only of a part of a single turn or may consist of two semicircular wries
through which a uni-directional current would flow in parallel or it may con-
sist of an arrangement of wires where the magnetic fields are two of opposite
polarity when exerted by a uni-directional electric current.
6
When the tube or rectangle is duplicated it may form a rotating or deflecting
'couple" and I can attain this end either by placing each tube or rectangle in
external fields of opposite polarity, if at the same time the electric current in
the shielded wire or wires. is flowing in the same direction (relative to space);
or by having the electric current in the shielded wire or wires flowing in opposite
directions relative to space (i.e. radially to or from a point between the two
tubes or rectangles) if at the same time both tubes or rectangles are placed in
the same magnetic field. In this last sentence it may be noted that although
I have spoken as if the current were a uni-directional one, it has only been for
the sake of clearness or convenience because, as before stated, these instruments
are intended primarily for use in alternating electric current circuits.
In addition to the balance and torsion methods of suspension and measurement,
I may use all the known and approved methods of suspension and control-from
the most delicate form of reflecting mirror instrument with uni-filar or bi-filar
suspensions or otherwise to these methods more adapted for commercial
instruments, I may use the zero method of measurements, or I may make them
direct reading instruments.
Dated this 14th day of September 1897
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow,
Applicant's Patent Agents.
Magnetic and Electric Measuring Instruments.
I, JAMES RUSSELL, Bridge Park, Selkirk, North Britain, Gentleman, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
My invention relates to instruments for the measurement of the magnetic
properties of iron, steel and other magnetic metals or materials, and they may
also be employed for measuring electric currents. My instruments for this
purpose of which there will be three or more modifications described and
which I shall call respectively A, B, C, etc., instruments--depend upon the
shielding properties of a tube or rectangle (to be hereafter defined) of iron etc.,
and I construct them in the following manner. Let coils of insulated wire be
constructed by preference two and of approximately rectangular or circular
shape and of any suitable proportions and if two coils be used, let them be
formed into a rigid system in such a way that the one side or portion of each coil
is near to one side or portion of the other coil. The wires of these sides or
portions of the coils will form the central wires and will be approximately
parallel if rectangular coils are used: These coils I shall call the internal coil
or coils of the instrument. The coils may consist of one, few, or many turns
of the insulated wire and must be connected in series in such a way that an uni-
directional electric current flowing through them will be in the same direction
in the central wires of the coils and consequently in the opposite direction in
all the external wires. The central wires will be called the central or shielded

page_text: wires and the external wires will be called the external wires. Let the
central wires be surrounded by a tube, or rectangle of iron or other
magnetic metal the magnetic properties of which are to be measured or deter-
mined. I wish it to be understood that by the words "tube or rectangle" I
mean not only a hollow structure of circular or approximately circular
section or rectangular section, but of any other section which may
be found most suitable. It may be of any suitable length or it
may be very short approximately to or in fact being al ring or
rectangle or other shape composed even of a single turn of wire of iron or other
magnetic metal or of any number of turns. I also include in my use of the
words tube or rectangle" all or any of the above structures which may have
been slit approximately lengthways or parallel to their axis, or otherwise, in
one, two, or any number of places and the slit or slits may either be very narrow
or they may be of great relative width, so that in extreme cases one side or part
thereof or two sides or part thereof of approximately rectangular structures may
be all that is left, or in the case of a circular or approximately circular section
one, two, or more arcs may be all that is left. I also include any built up
structure, and that even when it consists only in part of the iron etc., to be
examined; in fact I include any structure which exercises any effect however
slight in shielding the external field-to be afterwards mentioned from the
central or shielded wires. The tube or rectangle and internal coils must be of
suitable relative dimensions, so that they shall have entire freedom of motion
the one relative to the other, within the rather narrow limits which the nature
of this combined apparatus imposes upon their relative motions. This com-
bined arrangement of internal coils and tube or rectangle I place in a uniform
magnetic field or a field approximating thereto and which magnetic field I
shall call the external field-in such a way that the shielded and external
wires of the internal coils shall be at right angles-(or as nearly as possible) to
the lines of force of this external field. For the production of this external
field I use one, two, or more solenoids, which I shall call the external solenoid
or solenoids of suitable dimensions and suitably placed and adjustable relative
both to each other and the apparatus already described. The internal coils
and the external solenoids may be in series; or they may be excited by inde-
pendent electric currents. If now the internal coils be fixed relative to the
external field (or external solenoids) the tube or rectangle will move or tend
to move at right angles both to the lines of force of the external field and to its
own length (this being the same as the length of the shielded wires). On the
other hand if the tube or rectangle be fixed relative to the external field (or
external solenoids) the internal coils will move or tend to move at right angles
both to the lines of force of the external field and to the length of the shielded
(also external) wires. From the measurements of these forces, the
magnetic properties of the iron or other magnetic metal under test can be
determined, when the strength of the electric current is known, and, on the
other hand, the electric current may be measured when the magnetic properties
of the iron or other magnetic metal used, are known.
I mention that the force exerted by the tube or rectangle is equal and opposite
to the force exerted by the internal coil or coils. I may also find it necessary
or convenient to measure the force of the external wires plus the force of the
shielded wires and I may do this by measuring the force of rotation when at
least one (if more are used) of the internal coils is formed into a "couple." In
the event of my adopting one or a few turns of insulated wire for the internal
coil or coils, it would be necessary to have an additional coil or coils of many
turns in all respects similar to the internal coils only they would be fixed relative
both to the tube or rectangle and the external field. These fixed coils I shall
call the magnetising coils and they would also require to be so constructed
that they would allow the necessary freedom of motion of the internal coils

page_text: already described. The magnetising coils might be wound directly on the tube
or rectangle or otherwise.
This arrangement of additional magnetising coils would preclude the use
of the tube or rectangle from being a movable part of the instrument, i.e. it
could not be attached to the balance beam or otherwise as an alternative. I
have described the use of solenoids for the production of the external field, but
it must not be understood to imply that I might not use either permanent steel
magnets or electro-magnets, for the production of the external field. It must
also be understood that my use of the words electric current" must not be held
to imply that I might not use alternating electric currents in any or all of the
instruments. The above description applies generally to all the instruments, and
in particular I wish to point out that the introduction of the magnetising coils
in conjunction with the internal coil or coils or otherwise (and that with or
without the additional motion forming a rotating "couple "- thus giving the
internal coil a double possible motion) may form and in all probability will
form an important modification or important modifications of any or all of the
instruments for the measurement of magnetic properties of iron, &c., now to
be described.
Instrument A. This instrument may weigh the force exerted by either the
tube or rectangle or the internal coils if either the tube or rectangle or the in-
ternal coils be fixed at one end of a balance beam, suitably and delicately hung;
or if the parts are duplicated, at both ends of the balance beam. If the internal
coils are fixed to the beam at one end, or in the case of the duplication of the
parts at both ends of the balance beam, I will adopt some method by which
the electric current can be introduced into the internal coils whether it be by
means of mercury connections, or by silver or other wires fixed and adjusted
in such a way that they would serve the double purpose of carrying the electric
current and delicately and suitably hanging the balance beam. Or this instru-
ment may measure the force by means of a torsion wire or other suitable fibre
and the usual torsion head arrangement. In either case from one or a series of
weighings or measurements of the forces, the magnetic properties of the iron etc.
can be determined.
Instrument B. This instrument is similar to instrument A only it is essen-
tial that the parts be duplicated and that one of the tubes or rectangles be a
standard tube or rectangle with which the tube or rectangle under test can be
compared. This instrument must be so connected up electrically that the forces
exerted on opposite sides of the beam, oppose each other. It is therefore a
difference of two forces that is weighed or measured, from which can be deter-
mined by one or a series of observations the magnetic properties of the iron etc.
under test.
Instrument C. One side of this instrument remains the same as in instru-
ment A in which either tube or rectangle or internal coils are fixed to one end
of the balance beam. On the other side of the beam however I fix a coil of
insulated wire of any suitable number of turns, while one or more stationary
but adjustable coils of insulated wire are placed, one above or below (if only one
stationary-adjustable-coil be used) or one above and the other below (if two
stationary-adjustable-coils be used). The planes of these coils will be approxi-
mately horizontal if the balance beam alternative be used, or approximately
perpendicular if the torsion wire alternative be adopted. I shall call these
coils the balance coils. The internal coils and balance coils being connected
in series, I adjust, or approximate to such an adjustment the forces on the
opposite sides of the beam in such a way that the one would balance the other,
when the external field is supposed to be totally shielded from the central or
shielded wires. In this instrument therefore I measure the difference of two
opposing forces from which can be determined by one or a series of observatious
the magnetic properties of the iron or other magnetic metal under test.
These instruments may also be employed for the measurement of the electric

page_text: current (amperes), electric pressure (volts), and electric power (Watts) and that
on an alternating current circuit, although not to the exclusion of the uni-
directional current. For this purpose I utilise the arrangements generally
and the principles involved in a tube or rectangle shielding the central wire
or wires from an external magnetic field which have already been described.
Instruments B and C are obviously entirely unsuited for the purposes of measuring
the electric current. Instrument A, however, would measure the electric current
and the instrument could be designed to measure amperes, volts, or Watts
according to the known principles involved in the construction of these instru-
ments. My definition of the words "tube or rectangle" applies to these
instruments for measuring the electric current. The material used will in all
probability be soft iron. Great alterations are however made when necessary
in reducing the size and weight of the tube or rectangle, especially for delicate
instruments. The tube or rectangle may either be single or duplicated in which
case it may form a rotating or deflecting "couple." The internal coil or coils
may also consist of one, few, or many turns and I specify that the words "internal
coil" must not be held to imply that I might not use that part of a coil of a
single turn from which the external wire has been removed; in other words,
I distinctly specify that I may use a single wire, which however must correspond
to the central wire and must be shielded to a greater or less extent by the iron
ring or rectangle from the external field. The external solenoid or solenoids
may also consist of one, few, or many turns of insulated wire and it may also
consist only of a part of a single turn or may consist of two semicircular wires
through which a uni-directional current would flow in parallel or it may con-
sist of an arrangement of wires where the magnetic fields are two of opposite
polarity when exerted by a uni-directional electric current.
66
When the tube or rectangle is duplicated it may form a rotating or deflecting
'couple" and I can attain this end either by placing each tube or rectangle in
external fields of opposite polarity, if at the same time the electric current in
the shielded wire or wires is flowing in the same direction (relative to space);
or by having the electric current in the shielded wire or wires flowing in opposite
directions relative to space (i.e., radially to or from a point between the two
tubes or rectangles) if at the same time both tubes or rectangles are placed in
the same magnetic field. In this last sentence it may be noted that although
I have spoken as if the current were a uni-directional one, it has only been for
the sake of clearness or convenience because, as before stated, these instruments
are intended primarily for use in alternating electric current circuits.
In addition to the balance and torsion methods of suspension and measurement,
I may use all the known and approved methods of suspension and control-from
the most delicate form of reflecting mirror instrument with uni-filar or bi-filar
suspensions or otherwise to these methods more adapted for commercial
instruments, I may use the zero method of measurements, or I may make thein
direct reading instruments.
In order that my invention may be properly understood and readily carried
into effect I have hereunto appended two sheets of drawings, of which,
Instrument A. Figure 1 shews side elevation.
Figure 2 section through the line x, y (Figure 1).
Figure 3 end elevation as seen from (Figure 1).
Let coils AA, AA, of insulated wire be constructed, by preference two and
by preference of approximately rectangular section and if two coils be used let
them be formed into a rigid system and fixed in any suitable framework DD.
in such a way that one side or portion of each coil is near to one side or portion
of the other coil. The wires of these sides or portions of the coil will form the
central or shielded wires and will be approximately parallel if rectangular coils
be used. These coils I shall call the internal coil or coils, and they may consist
of any number of turns of insulated wire and must be connected in series in such
a way that a unidirectional electric current flowing through them will be in

page_text: the same direction in the central wires and consequently in the opposite direction
in all the external or return wires of the internal coils. Let the central wires
be surrounded in whole or in part by the iron or steel &c., the magnetic properties
of which are to be measured or determined. For the purposes of convenient
introduction into the instrument I prefer to use two pieces of iron each bent
approximately into the form of the letter and of sufficiently long sides so that
they may overlap to some extent and thus diminish the air reluctance of the
magnetic circuit. These pieces of sheet iron are shewn separately in Figure 4,
a being the end elevation as seen from (Figure 1) and b the side elevation.
(Each of these bent pieces of iron however may be composed of more than one piece.)
Between the sides of these two pieces of iron I prefer to insert thin pieces of sheet
ebonite marked P or other suitable non-magnetic material, shown in Figure 2
instead of having the pieces in contact. They may however be in
contact. Each piece of iron is slipped into a light rigid frame-
work G G, the one piece from above and the other piece from below and they
are held in position by wedge shaped pieces H H or fixed by any other
suitable and convenient means. The framework GG is in its turn connected
with the balance beam FF FF which is rigidly constructed and free to turn
about its centre being suspended on the usual knife edges or any other mode of
suspension such as silk fibres or ribands, and capable of adjustment so that the
framework GG and consequently the iron under test and now called the shield
may move freely in or about the axis of the internal coils. The balance beam is
provided with divided scale or divided scales and riders by means of which the
force experienced by the iron is weighed, and the beam is calibrated to give
readings at all current strengths.
This combined arrangement of internal coils and iron shield I place in a
magnetic field, by preference a uniform magnetic field or as nearly so as con-
venient structural arrangements will allow, which magnetic field I shall call
the external field in such a way that the central wires of the internal coils shall
be as nearly as possible at right angles to the lines of force of this external field;
while the direction of possible motion of the shield is as nearly as possible at
right angles both to the lines of force of the external field and to the central
wires.
For the production of this external field I use by preference, two coils of
insulated wire, to be called the external coils BB BB, wound upon a suitable
framework CC, which may be used to support the internal coils, all as shown.
The block L L firmly fixed to the base board MM supports the framework CC
and the supports from or on which the balance beam is suspended. When a
current of electricity is sent through both the internal and external
coils of the instrument, these coils being either in series or excited by inde-
pendent electric currents, the shield moves or tends to move at
right angles both to the lines of force of the external field and
to the length of the central wires, and this in the balance form of the instru-
ment is up or down according to the relative direction of the currents in the
external and the internal coils. This force, which is proportional to the shield-
ing, being weighed at all stages of current strength and consequently at all
stages of magnetisation of the iron within the limits determined by the number
of turns of the coils and the maximum current strength used, I determine the
magnetic properties of the iron forming the shield.
To conveniently take the iron through all stages of magnetisation I arrange
commutators and current reversers by preference on the base board of the
instrument by means of which I can reverse the current from a positive maximum
to a negative maximum or from a positive maximum to any less current of the
same sign or from a positive maximum to any less current of the opposite sign
or vice versa. For the more exact manipulation of the instrument, I prefer to
wind all the coils double in such a way that each coil consists of two distinct
coils on which the electric current may flow in the same or in opposite directions,

page_text: in which latter case no available magnetic fields are created. This is arranged
by means of commutators by preference also on the baseboard of the instrument
so that the magnetic field either of the internal or external coils can be con-
veniently cut out separately without altering the resistance of the circuits and
consequently without altering the current strength in use at the time. These
arrangements allow zero corrections to be made. None of the commutators are
shewn in the drawings, as they are constructed and arranged on well known
principles, which are or may be in common use.
A modification of this instrument is shewn in Figure 5, and consists in
arranging the external or return wires of the internal coils at some little distance
or any required distance away from the shield, the balance beam being also
modified to suit the altered arrangements. In this manner a greater force is
experienced by the shield relative to the current strength employed, especially
at the earlier stages of megnetisation. The permeability of the iron being less
quickly reduced the shielding is more perfect.
The external coils BBBB shewn in Figures 1, 2 and 3 can be replaced by
one or two circular coils, so arranged that the points of suspension of the balance
beam K be in the axis of these coils. Figure 6 is a plan and Figure 7 is a
section on line x, y, shewing this method adopted for a smaller form of instru-
ment where the force experienced by the shield is measured by the torsion of a
wire M or spring and the usual pointer R and torsion head arrangements such
as are used in Siemen's Electro Dynamometer and other zero instruments, and
is consequently not shewn in the drawings. The arrangements of internal
coils and shield may be similar to that adopted in Figures 1, 2, and 3 or in
Figure 5. I have however adopted another arrangement for the internal coil
in which one or many straight insulated conductors A A confined by preference
in a tube, form a diameter of the external coils BBB B. If more than one
wire be used (as the wires AA) they are connected in series (by preference
beyond the external coils BBB B) by means of other wires in such a way that
a unidirectional current flowing through them is in the same direction in all
the straight insulated conductors A A. Surrounding these conductors is a brass
or other tube L connected by means of the torsion wire M with the usual torsion
head arrangement already mentioned. This tube of circular or other section
must be of sufficient internal diameter or section to allow sufficient freedom of
motion for the measurement of the forces experienced when surrounded in whole
or part by the shield. The shield may be in two pieces bent as in Figure 4
and slipped on to the carrying tube L from opposite sides, being held in position
by any convenient arrangement which is sufficiently obvious and need not be
detailed, or it may be in one piece, bent round the carrying tube L. If iron or
steel wire is to be tested it may be wound round the carrying tube and is shewn
in Figures 6 and 7, NN.
Instruments B are similar to instruments A only it is essential that in
Figures 1, 2, 3, and 5, the parts be duplicated, thereby making the arrangements
of external coils, internal coils and shield, similar on opposite ends of the balance
beam. A standard shield is introduced into the one side of the instrument,
similar and equal to the iron under test on the opposite side and the electric
currents in the coils are so arranged that the forces oppose each other. It is
therefore a difference of forces which is weighed or measured from which can
be determined by one or a series of observations the magnetic properties of the
iron under test. The instruments shewn in Figures 6 and 7 can be used in this
way without any alteration further than that, carrying tube L would have a
shield on both sides of the point of suspension. When a second shield be placed
or wound on the right side of the carrying tube, the forces necessarily oppose
each other and as above the difference of two forces is measured.
I also use instruments A for the measurement of the electric current but for
this purpose I prefer to use a shield of soft iron which does not constitute a
closed or practically closed magnetic circuit, but has been split lengthways

page_text: parallel to its axis at several places and without overlapping of parts. The
iron parts which now constitute the shield may be fixed directly to the frame-
work G or they may be mounted on two light frames, which can slip into the
framework G in the place of the iron shields and pieces of sheet ebonite hitherto
described. The iron parts constituting the shield may be still further, reduced
to two or more sides or arcs of the original shield and this is shewn in Figure VIII
where the moving part of instruments 6 and 7 is utilised for the support of the
arcs. Figure 8, a shews the end view while b shews the top view.
When the coils of these instruments are in series the readings will be propor-
tional to the square of the current within the limits for which the instruments
have been arranged. When they are used as Wattmeters I prefer that the ampere
current excites the external coils and the voltage current the shielded wires.
I now shew an instrument for the measurement of large currents. Figure IX
shews the top view, Figure X the side elevation, and Figure XI the front eleva-
tion. In this arrangement the electric current flows through the instrument
in multiple arc in such a way that the moving part forms a rotating "couple."
as will afterwards appear. The copper conductors are shewn of rectangular
section. C and D are the terminals of the instrument and if the electric current
enters by the terminal C it will pass along the conductor EE till it reaches the
top part of the conductor where it will divide, one half of the current flowing
through A to the semicircular conductor BB hence by means of A¹ to the lower
semicircular conductor B¹ and so to the bottom of the instrument A", while
the other half of the current will follow the course as indicated by the sequence
of the following letters A B A B A¹, the currents again joining and
flowing to the terminal D by means of the conductor F and so completing the
circuit of the instrument. The direction of the current is also shewn by the
arrows and it will be observed that it flows in one direction round the two top
semicircular conductors B, B" and in the opposite direction round the two
lower semicircular conductors B¹, B¹¹. This creates a radial magnetic
field between the upper and lower systems of conductors and it is a practically
uniform field in so far as the motion of the moving part carrying the shield is
concerned. This field corresponds to the external magnetic field. It will also
be observed that the conductors A, A¹ A and A1 Ain All constitute prac-
tically two linear currents in multiple arc, which correspond to the internal
or shielded wires. It is therefore evident that if those portions of the linear
currents lettered A¹ and A be surrounded in whole or in part by shield of
soft iron as shewn in Figures VIII and connected by a light arm free to rotate
in centre L which is in the axis of the system of circular conductors, this moving
part will form a rotating "couple" the forces experienced by the shields supple-
menting each other. I measure this force by the usual pointer fixed to the
moving part, torsion wire and the well known torsion head arrangement which
have already been mentioned, more particularly in connection with Figures 6
and 7 or otherwise.
I have shewn however an arrangement whereby the instrument is made a
direct reading one by using only an iron shield H & H at one side of the con-
ductors A and A, and I place these two shields at the side of these conduc-
tors at which there is apparent repulsion. Q is the pointer in connection with
the moving part and P the divided scale. The moving part is suspended by a
fine torsion wire which also forms the control: This arrangement is shewn
separately in Figure XII. The torsion wire is fixed by means of adjustable
caps at the top and bottom of a long tube SS and the lower part of the tube
may be expanded so as to form a well T for oil in which a vane V in rigid con-
nection with the moving part is immersed. The middle part of the tube must
be sufficiently cut away on opposite sides in such a manner that the moving
part is free to rotate through an angle of about 90°. This arrangement must
be so constructed that it can be readily introduced into the system of conductors
and may either be fixed directly to but insulated from the conductors at P and P

page_text: where semicircular grooves have been left for the purpose; or both systems can
be fixed to the framework of the instrument. In adjusting the zero of the
instrument it is necessary that the shields H H be not too near the conduc-
tors AA, otherwise they will be attracted to the conductors although with
a less force than if there had been no shielding.
The moving part may also be suspended in any approved manner such as fine
points working in jewelled cups and the control may be springs or gravity
control. In this latter case Figure XI will become the top view of the instru-
ment, Figure IX the end elevation and Figure X the side elevation. As these
modes of suspension and control are well known to makers of electrical and
other delicate instruments these alternative methods are not shewn in the
drawings as they do not constitute any special features of the instruments. It
is essential however, that the moving part may be delicately suspended and
balanced. The framework has in like manner not been shewn.
For zero instruments the shield H shewn in Figures 9, 10, 11, and 12. may
be extended so as to nearly fill up the semicircular spaces between B and B¹
and B and B. In this case the iron shield would be cut up in sections radially
or built up of iron, wire or otherwise.
A zero wattmeter for large currents is constructed by reducing the size of the
instrument shewn in Figures and 7 and reducing the number of turns in the
coils B to one or a few turns each. The wires A A would be in series with a
non-inductive resistance and would carry the voltage current.
The moving
(
part could also be in duplicate in which case the voltage wires A A would remain
as shewn but the coils for the creation of the external field and which carry the
ampere current would be so arranged that the moving part, now forming a
couple" would be in fields of opposite polarity. These coils could either be
in series or in mutiple arc and this latter arrangement is shewn in Figure XIII,
which shews the top view. A A are the wires carrying the voltage current,
BB the conductor forming the coils in multiple arc, which are in duplicate one
above and the other below the moving part, C and D are their terminals. NNNN
are the iron oblates carried by the movable part and Q the zero pointer. The
control may either be a torsion wire or delicate spring and the torsion head
arrangement the same as in Siemen's Electro Dynamometer and is consequently
not shewn.
The above instruments, where the "couple" is free to rotate in magnetic fields
of opposite polarity, are independent of the earth's magnetic field and I have
consequently only shown drawings of these forms and not of the alternative
forms of couple," which may be constructed when there is only one external
magnetic field.
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 method of determining the magnetic properties of iron &c., by utilising
the effect which iron, steel, &c. exercises in shielding a conductor or system of
conductors from a magnetic fleld, substantially as described and illustrated on
the accompanying sheets of drawings.
2. The method of measuring electric currents by utilising the effect which
iron, steel, &c., exercises in shielding a conductor or system of conductors from
a magnetic field, substantially as described and illustrated on the accompanying
sheets of drawings.
Dated this 14th day of June 1898
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow,
Applicant's Patent Agents.