Year: 1885

page_text: I ADAM MILLAR of 176 Ingram Street, Glasgow, in the County of Lanark,
Electrician, do hereby declare the nature of this invention to be as follows :-
The purpose of the instrument is to measure the magnetic intensity of magnets
and electro-magnets, and the principle on which the instrument acts is by shewing
the force of the attraction which a magnet exerts upon an armature of soft iron,
placed at a small distance from the magnet.
In the accompanying sheet of drawings Figure 1, shews a front elevation, and
Figure 2, a side elevation of the instrument.
A brass tube A forms a jacket or body for a second brass tube B to slide within
it in telescope fashion, its movement being produced by the pinion P carried by
the outer tube A, and the rack R carried by the inner tube B.
The inner tube B has a cap or cover C in which an adjusting screw D works, the
lower end of the screw carries a spiral spring E. of brass or other non-magnetic
metal, and at the lower end of the spring a light armature F. is attached. The
armature is made of soft iron, in the form of a hollow cylinder.
An opening is made in the front of the tubes A. and B., so as to allow the upper
half of the armature to be readily seen.
A plate G is fixed in the tube A, to act as a guide to keep the armature in the
centre of the tube, an opening being made in the plate through which the
armature passes freely.
The front edge of the plate G is filed away so as to present two narrow flat
surfaces H, H, with a space between them which is filled up by the cylindrical
surface of the armature.
A reading line or mark is cut upon the surfaces H, H, and a circular line is cut
upon the cylindrical surface of the armature. When the armature is in the normal
position, the circular line should be exactly opposite the line or mark on the
surfaces H, H.
The tube A carries a base piece J, and the base piece should be so adjusted that
the distance between the lower end of the armature and the lower side of the base
piece should be a definite distance,-say for example, five milimetres.
In using the instrument, it is placed with its base resting on the pole of the
magnet to be measured, the attractive action of the magnet will draw the armature
downwards against the upward pull of the spiral spring. The tube B which carries

page_text: the spiral spring is then to be raised by turning the pinion P. until the upward
pull of the spring is just sufficient to bring the armature back to its normal
position.
The distance which the spring has to be stretched, as shewn by the distance
which the tube B has to be raised, to produce the equilibrium of the magnet and
spring, is the measure of the attractive force of the magnet upon the armature at
the distance of five milimetres.
As the attractive action of the magnet upon the armature increases rapidly as
the distance between them is lessened, it is of advantage that stops should be
formed so as to limit the movement of the armature to a very small distance on
each side of the normal position.
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A graduated scale is formed on the tube B, each degree representing the attractive
force of magnets of known intensities, from zero to complete saturation, or, the
scale may be formed on the basis of gravity as the unit, each division of the
scale representing the pull of a known weight in addition to the weight of
the armature.
Other methods may be adopted for indicating the force of the pull of the magnet
upon the armature, for instance, a small balance of the ordinary form, or, of the
form known as a steelyard, but the spring balance as described is to be preferred on
account of its compactness, and freedom from any error arising from friction.

page_text: I, ADAM MILLAR of Number One hundred and seventy six Ingram Street,
Glasgow, in the County of Lanark, Electrician do hereby declare the nature of
my invention for AN IMPROVED MAGNETOMETER and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:-
The purpose of the instrument is to measure the magnetic intensity of. Magnets
and Electro-magnets, and the principle on which the instrument acts is by shewing
the force of the attraction which a magnet exerts upon an armature of soft iron,
placed at a small distance from the magnet.
In the accompanying sheet of drawings Fig. 1, shews a front elevation, and
Fig. 2. a side elevation of the instrument.
A brass tube A forms a jacket or body for a second brass tube B to slide within
it in telescope fashion, its movement being produced by the pinion P, carried by
the outer tube A, and the rack R carried by the inner tube B.
The inner tube B has a cap or cover C, in which an adjusting screw D works, the
lower end of the screw carries a spiral spring E, of brass or other non-magnetic
metal, and at the lower end of the spring a light armature F is attached.
The armature is made of soft iron in the form of a hollow cylinder.
An opening is made in the front of the tubes A and B, so as to allow the upper
half of the armature to be readily seen.
A plate G is fixed in the tube A to serve as a guide to keep the armature in the
centre of the tube, a circular opening is made in the centre of the plate through
which the armature passes freely.
The front part of the plate G is filed away so as to form two narrow flat
surfaces H, H, with a space between them in which the cylindrical surface of the
armature appears.
A reading line or mark is cut upon the surfaces H, H, and a circular line is
formed on the cylindrical surface of the armature. When the armature is in its
normal position, the circular line on the armature should be exactly opposite the
reading line or mark on the surfaces H, H.
The tube A carries a base piece J, and the base should be so adjusted that the
distance between the lower end of the armature, and the lower side of the base
piece should be a known and definite distance, say for example five milimetres.
In using the instrument, it is placed with its base resting upon the pole of the
magnet which is to be measured, when the attractive action of the magnet will
draw the armature downwards against the upward pull of the spiral spring. The
tube B which carries the spring is then raised by turning the pinion P, until the
upward pull of the spring is just sufficient to bring the armature back to its normal
position.
The distance which the tube B, has to be raised to produce this equilibrium is
the measure of the attractive force of the magnet upon the armature at the distance
of five milimetres.

page_text: As the attractive action of the magnet upon the armature increases rapidly as
the distance is lessened, it is of advantage that stops should be inserted so as to
limit the movement of the armature to a very small distance above and below the
normal position.
A graduated scale is formed on the tube B, each degree representing the attractive
force of magnets of known magnetic intensity, from zero to complete saturation, or
the scale may be formed on the basis of gravity as the unit, each division of the
scale representing the pull of a known weight in addition to the weight of the
armature.
Other methods may be adopted for indicating the force of the pull of the magnet
upon the armature, for instance a small balance of the ordinary form, or, of the
form known as a steel-yard, but the spring balance as described is to be preferred
on account of its compactness.
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:
An Instrument for indicating the magnetic intensity of Magnets and Electro-
magnets, which acts by measuring the attractive force which a magnet exerts
upon a small armature placed near to the pole of the magnet, substantially as
described.