Year: 1885

page_text: I JAMES BLYTH, M.A, of Anderson's College, Glasgow, in the County of Lanark,
North Britain, Professor of Natural Philosophy and Mathematics, do hereby
declare the nature of this invention to be as follows that is to say:-
My said Invention has for its object to improve the construction of galvano-
meters so as to obtain indications of the strengths of electric currents in a simple
form, and other advantages.
In one modification of my improved galvanometers two bundles of permanently
magnetised steel wires are made up in the form of cylinders having narrow axial
holes. These are fixed with their axes in the same vertical line, separated by a
narrow gap, and so that the north poles of the one set of magnets face the south
poles of the other. In this gap the magnetic field is sensibly uniform and the lines
of force vertical. Inserted in the gap is a thin circular disc of wood or vulcanite,
having a central mercury cup and a concentric circular mercury trough at a 'short
distance from it. A stout bruss rod is provided having a short thick copper wire
rigidly attached at right angles to its lower end. Its upper end passes freely through
the axial hole in the upper magnet, and is rigidly attached to the lower end of a long
fine torsion wire of steel or silver, whose upper end is fixed to a suitable support.
A fibre of whale bone or other suitable material may be substituted for the torsion
wire and a tube may be substituted for the brass rod the torsion wire or fibre being
passed down through the tube and attached to the lower end. The lower end of the
brass rod dips into the central mercury cup, and the outer end of the copper wire,
(hent down a little at right angles) dips into the concentric caual of inercury. Stont
copper wires are led from the ceutral cup and canal to binding-screws suitably
place so as to form the terminals of the instrument. The upper end of the brass
rod, which projects a little above the upper magnet, carries a long pointer, which
moves over a horizontal circular dise, graduated either to degrees or to show
amperes directly. This disc is fixed with the torsion wire passing freely through
its centre. The whole is so enclosed as to be free from air current.
The action of the instrument will be easily understood.-Suppose a current sent
through it. As is well known, the electromagnetic force acting on the radial
current will tend to make it rotate in a horizontal plane with a uniform force.
This rotation will go on tilfa certain angle is reached, when the moment due to the

page_text: electromagnetic force is balanced by the monent due to the torsion of the wire.
In this modification the current strength is proportional to the angle of deflection.
In a second modification the permanent magnets are replaced by similarly
placed electromagnetic coils, through which the current to be measured passes.
In this case the square of the current strength is proportional to the angle of
deflection.
In another modification the fixed magnets are dispensed with, and instead, a
cylindrical bundle of magnets is fixed coaxially to the brass rod, but insulated from
it, so that it rotates along with the rod and radial wire. In this case the radial
wire projects from the middle of the length of the magnet bundle, while the lower
end of the brass rod is prolonged so as to dip into a mercury cup at a consider-
able distance below the lower end of the bundle. Owing to the influence of the
exterior part of the circuit leading from the merenry canal to the cup, the equation
for this case is a little more complicated. With proper arrangements, however, the
deflection can be shown to be proportional to the current strength.
In the instruments constructed for practical use the mercury cup and canal are
so made on the unspillable ink-bottle principlé, as to preserve the mercury in case
of being knocked over or even inverted.
Dated this fourteenth day of Santamber 1885
EDMUND HUNT,
Applicant's Agent.
COMPLETE SPECIFICATION.
Improvements in Galvanometers.
I, JAMES BLYTH, M.A. of Anderson College, Glasgow, in the County of Lanark,
North Britain, Professor of Natural Philosophy and Mathematics 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, that
is to say:
-
My Invention consists in placing in the same vertical line two cylindrical
magnets having narrow axial holes and made up of bundles of permanently
magnetised steel wires and separated by a narrow gap in which gap the magnetic
field is sensibly uniform and the lines of force vertical. A stout brass rod is
suspended in the axis of the magnets by a fine torsion wire or fibre fixed at the
top. The brass rod has fixed to it a radial copper wire the outer end of which is
bent down and dips into a concentric annular mercury trough while the brass rod
itself dips into a central mercury cup. The trough and cup are connected with the

page_text: terminals of the instrument.
An index or pointer may be fixed to the brass rod
to move over a graduated disk or a graduated disk may be fixed to the rod and
may either show degrees or amperes directly.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append a sheet of explanatory drawings to
be hereinafter referred to and showing a convenient arrangement of my improved
galvanometer.
Figure, 1, is a plan; figure, 2, a side elevation; figure, 3, a horizontal section of
one compound magnet and figure, 4, a vertical section. In these drawings the
same reference numerals are used to mark the same or like parts wherever they
are repeated.
In carrying out my Invention two magnets, 5, 6, consisting of bundles of
permanently magnetised steel wires or rods are made up in the form of cylinders
having narrow axial holes. These are fixed with their axes in the vertical line
separated by a narrow gap, 7, so that the north poles of the one set of magnets
face the south poles of the other. The outer ends of each set of magnets wires or
rods, 5, 6, are fixed in flanged cups, 8, 9, of suitable iron and these cups, 8, 9, are
connected together by four iron rods, 10, the connecting of the parts in this way
greatly increasing the strength of the magnetic field. In the gap, 7, between each
set of magnets 5, 6, the magnetic field is sensibly uniform and the lines of force
vertical. The gap, 7, is enclosed and the inner ends of the wires of each set of
magnets 5, 6, are bound together by two rings, 11, 12, which may be made of
wood or vulcanite, the lower ring, 12, having a concentric annular mercury
through, 13, formed in its upper surface. A small bottle, 14, partly filled with
mercury is held by a wire, 15, the upper end of which is fixed to a small bracket
movable on one of the rods, 10, but fixed in any desired position by a small
pinching screw, 16. Connected to the bottom of the bottle, 14, is a flexible
tube, 17, the other end of which communicates through a small casing, 18, with
the concentric annular mercury trough, 13, and by raising or lowering the
bottle, 14, mercury can be run into or withdrawn from the trough, 13. Thus
when carrying the instrument from one place to another the bottle, 14, may be
lowered to receive the mercury and the communication can be closed by a valve, 19,
fitted to the casing, 18.
A brass rod, 20, passes freely through the axial hole in the lower magnet, 6, and
has rigidly attached to its upper end a fine torsion wire, 21, of steel or silver
whose upper end is adjustably fixed to a support, 22, made of wood or vulcanite
and fixed in the upper cup, 8. A fibre of whale bone or other suitable material
may be substituted for the torsion wire and a tube may be substituted for the
brass rod the torsion wire or fibre being being passed down through the tube and
attached to the lower end. The lower end of the brass rod, 20, dips into a central
mercury cup, 23, formed in a disk, 24, of wood or vulcanite and which disk also
serves as a stand for the instrument. A ring, 25, inclined downwards towards
the middle is placed a little above and round the mercury cup, 23, to prevent
the mercury froin escaping when the instrument is turned down or inverted, the
bottom of the space being inclined downwards to the cup so that the mercury may
run into the cup when the instrument
placed in the upright position. At or near
the upper end of the brass rod, 20,
is fixed a copper wire, 26, the outer end of
which is bent down at right angle dips into the concentric annular mercury
trough, 13. Stout copper wires, 27, are led from the central mercury cup, 23, and
from the concentric annular mercury trough, 13, to binding screws, 28, which form
the terminals of the instrument. The lower end of the brass rod, 20, has fixed to
it a circular disk, 29, the upper surface of which is graduated either to degrees or
to show amperes directly. This graduated disk, 29, is enclosed in the stand, 24, so
as to be free from air currents. A small sight hole, 30, is formed in the upper
surface of the stand, 24, over the graduated disk, 29, to allow of adjustinent and
of the indications being read. The stand, 24, is also provided with adjusting or
levelling screws, 31.

page_text: The action of the instrument will be easily understood. Suppose a current sent
through it.
As is well known, the electromagnetic force acting on the radial current.
will tend to make the wire, 26, rotate in a horizontal plane with a uniform force.
This rotation will go on until a certain angle is reached, when the moment due
to the electromagnetic force is balanced by the moment due to the torsion of
the wire.
In
In a second modification the permanent inaguets are replaced by similarly
placed electromagnetic coils through which the current to be measured pas es.
this case the square of the current strength is proportional to the angle of
deflection.
In another modification the fixed magnets are dispensed with and instead a
cylindrical bundle of magnets is fixed coaxially to the brass rod but insulated from
it so that it rotates along with the rod and the radial wire. In this case the
radial wire projects from the middle of the length of the magnet bundle while the
lower end of the brass rod is prolonged so as to dip into a mercury cup at a
considerable distance below the lower end of the bundle. Owing to the influence
of the exterior part of the circuit leading from the mercury canal to the cup the
equation for this case is a little more complicated. With proper arrangements
however the deflection can be shown to be proportional to the current strength.
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 improved construction of galvanometer in which a radial conductor for the
current to be measured and subjected to the rotational force due to the action of
the current and an annular magnetic field the lines of force of which are at right
angles to the plane of rotation, is suspended by a wire or fibre the torsional
resistance of which is shown by the extent of rotation of the radial conductor and
constitutes a measure of the current substantially as hereinbefore described.
Dated this eleventh day of June 1886.
EDMUND HUNT,
Applicant's Agent.

page_text: I JAMES BLYTH, M.A, of Anderson's College, Glasgow, in the County of Lanark,
North Britain, Professor of Natural Philosophy and Mathematics, do hereby
declare the nature of this invention to be as follows that is to say :-
My said Invention has for its object to improve the construction of galvano-
meters so as to obtain indications of the strengths of electric currents in a simple
form, and other advantages.
In one modification of my improved galvanometers two bundles of permanently
magnetised steel wires are made up in the form of cylinders having narrow axial
holes. These are fixed with their axes in the same vertical line, separated by a
narrow gap, and so that the north poles of the one set of magnets face the south
poles of the other. In this gap the magnetic field is sensib'y uniform and the lines
of force vertical. Inserted in the gap is a thin circular disc of wood or vulcanite,
having a central mercury cup and a concentric circular inercury trough at a short
distance from it. A stout brass rod is provided having a short thick copper wire
rigidly attached at right angles to its lower end. Its upper end passes freely through
the axial hole in the upper magnet, and is rigidly attached to the lower end of a long
fine torsion wire of steel or silver, whose upper end is fixed to a suitable support.
A fibre of whale bone or other suitable material may be substituted for the torsion
wire and a tube may be substituted for the brass rod the torsion wire or fibre being
passed down through the tube and attached to the lower end. The lower end of the
brass rod dips into the central mercury cup, and the outer end of the copper wire,
(bent down a little at right angles) dips into the concentric canal of mercury. Stout
copper wires are led from the central cup and canal to binding-screws; suitably
placed so as to form the terminals of the instrument. The upper end of the brass
rod, which projects a little above the upper magnet, carries a long pointer, which
moves over a horizontal circular disc, graduated either to degrees or to show
amperes directly. This disc is fixed with the torsion wire passing freely through
its centre. The whole is so enclosed as to be free from air current.
The action of the instrument will be easily understood.-Suppose a current sent
through it. As is well known, the electromagnetic force acting on the radial
current will tend to make it rotate in a horizontal plane with a uniform force..
This rotation will go on till a certain angle is reached, when the moment due to the
Emine 71

page_text: electromagnetic force is balanced by the moment due to the torsion of the wire.
In this modification the current strength is proportional to the angle of deflection.
In a second modification the permanent inagnets are replaced by similarly
placed electromagnetic coils, through which the current to be measured passes.
In this case the square of the current strength is proportional to the angle of
deflection.
In another modification the fixed magnets are dispensed with, and instead, a
cylindrical bundle of magnets is fixed coaxially to the brass rod, but insulated from
it, so that it rotates along with the rod and radial wire. In this case the radial
wire projects from the middle of the length of the magnet bundle, while the lower
end of the brass rod is prolonged so as to dip into a mercury cup at a consider-
able distance below the lower end of the bundle. Owing to the influence of the
⚫ exterior part of the circuit leading from the mercury canal to the cup, the equation
for this case is a little more complicated. With proper arrangements, however, the
deflection can be shown to be proportional to the current strength.
In the instruments constructed for practical use the mercury cup and canal are
so made on the unspillable ink-bottle principle, as to preserve the mercury in case
of being knocked over or even inverted.
Dated this fourteenth day of September 1885.
Improvements in Galvanometers.
I, JAMES BLYTH, M.A. of Anderson College, Glasgow, in the County of Lanark,
North Britain, Professor of Natural Philosophy and Mathematics 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, that
is to say:
My Invention consists in placing in the same vertical line two cylindrical
magnets having narrow axial holes and made up of bundles of permanently
magnetised steel wires and separated by a narrow gap in which gap the magnetic
field is sensibly uniform and the lines of force vertical. A stout brass rod is
suspended in the axis of the magnets by a fine torsion wire or fibre fixed at the
top. The brass rod has fixed to it a radial copper wire the outer end of which is
bent down and dips into a concentric annular mercury trough while the brass rod
itself dips into a central mercury cup. The trough and cup are connected with the

page_text: terminals of the Instrument.
An index or pointer may be fixed to the brass rod
to move over a graduated disk or a graduated disk may be fixed to the rod and
may either show degrees or amperes directly.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append a sheet of explanatory drawings to
be hereinafter referred to and showing a convenient arrangement of my improved
galvanometer.
Figure, 1, is a plan; figure, 2, a side elevation; figure, 3, a horizontal section of
one compound magnet and figure, 4, a vertical section. In these drawings the
same reference numerals are used to mark the same or like parts wherever they
are repeated.
In carrying out my Invention two magnets, 5, 6, consisting of bundles of
permanently magnetised steel wires or rods are made up in the form of cylinders
having narrow axial holes. These are fixed with their axes in the vertical line
separated by a narrow gap, 7, so that the north poles of the one set of magnets
face the south poles of the other. The outer ends of each set of magnets wires or
rods, 5, 6, are fixed in flanged cups, 8, 9, of suitable iron and these cups, 8, 9, are
connected together by four iron rods, 10, the connecting of the parts in this way
greatly increasing the strength of the magnetic field. In the gap, 7, between each
set of magnets 5, 6, the magnetic field is sensibly uniform and the lines of force
vertical. The gap, 7, is enclosed and the inner ends of the wires of each set of
magnets 5, 6, are bound together by two rings, 11, 12, which may be made of
wood or vulcanite, the lower ring, 12, having a concentric annular mercury
through, 13, formed in its upper surface. A small bottle, 14, partly filled with
mercury is held by a wire, 15, the upper end of which is fixed to a small bracket
movable on one of the rods, 10, but fixed in any desired position by a small
pinching screw, 16. Connected to the bottom of the bottle, 14, is a flexible
tube, 17, the other end of which communicates through a small casing, 18, with
the concentric annular mercury trough, 13, and by raising or lowering the
bottle, 14, mercury can be run into or withdrawn from the trough, 13. Thus
when carrying the instrument from one place to another the bottle, 14, may be
lowered to receive the mercury and the communication can be closed by a valve, 19,
fitted to the casing, 18.
A brass rod, 20, passes freely through the axial hole in the lower magnet, 6, and
has rigidly attached to its upper end a fine torsion wire, 21, of steel or silver
whose upper end is adjustably fixed to a support, 22, made of wood or vulcanite
and fixed in the upper cup, 8. A fibre of whale bone or other suitable material
may be substituted for the torsion wire and a tube may be substituted for the
brass rod, the torsion wire or fibre being being passed down through the tube and
attached to the lower end. The lower end of the brass rod, 20, dips into a central
mercury cup, 23, formed in a disk, 24, of wood or vulcanite and which disk also
serves as a stand for the instrument. A ring, 25, inclined downwards towards
the middle is placed a little above and round the mercury cup, 23, to prevent
the mercury from escaping when the instrument is turned down or inverted, the
bottom of the space being inclined downwards to the cup so that the mercury may
run into the cup when the instrument is placed in the upright position. At or near
the upper end of the brass rod, 20, there is fixed a copper wire, 26, the outer end of
which is bent down at right angles and dips into the concentric annular mercury
trough, 13. Stout copper wires, 27, are led from the central mercury cup, 23, and
from the concentric annular mercury trough, 13, to binding screws, 28, which form
the terminals of the instrument. The lower end of the brass rod, 20, has fixed to
it a circular disk, 29, the upper surface of which is graduated either to degrees or
to show amperes directly. This graduated disk, 29, is enclosed in the stand, 24, so
as to be free from air currents. A small sight hole, 30, is formed in the upper
surface of the stand, 24, over the graduated disk, 29, to allow of adjustment and
of the indications being read. The stand, 24, is also provided with adjusting or
levelling screws, 31,

page_text: The action of the instrument will be easily understood. Suppose a current 'sent
through it. As is well known, the electromagnetic force acting on the radial current
will tend to make the wire, 26, rotate in a horizontal plane with a uniforin force.
This rotation will go on until a certain angle is reached, when the moment due
to the electromagnetic force is balanced by the moment due to the torsion of
the wire.
In a second modification the permanent magnets are replaced by similarly
placed electromagnetic coils through which the current to be measured passes. In
this case the square of the current strength is proportional to the angle of
deflection.
.
In another modification the fixed magnets are dispensed with and instead a
cylindrical bundle of magnets is fixed coaxially to the brass rod but insulated from
it so that it rotates along with the rod and the radial wire. In this case the
radial wire projects from the middle of the length of the magnet bundle while the
lower end of the brass rod is prolonged so as to dip into a. mercury cup at a
considerable distance below the lower end of the bundle. Owing to the influence
of the exterior part of the circuit leading from the mercury canal to the cup the
equation for this case is a little more complicated. With proper arrangements
however the deflection can be shown to be proportional to the current strength.
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 improved construction of galvanometer in which a radial conductor for the
current to be measured and subjected to the rotational force due to the action of
the current and an annular magnetic field the lines of force of which are at right
angles to the plane of rotation, is suspended by a wire or. fibre the torsional
resistance of which is shown by the extent of rotation of the radial conductor and
constitutes a measure of the current substantially as herein before described.
Dated this eleventh day of June 1886
EDMUND HUNT,
Applicant's Agent.