MENTS IN MAGNETOMETERS
Year: 1886

page_text: Equivalents.
I ADAM MILLAR of number forty-five Montrose Street, Glasgow, in the County
of Lanark, Electrician do hereby declare the nature of my invention for IMPROVE-
MENTS IN MAGNETOMETERS and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
The essential principle of the invention is described as follows: One or more
small bars of soft iron are attached to an axis which is free to turn between
suitable bearings carried by a suitable frame work.
When the armatures on the axis are placed near to the pole of a magnet, and so
placed that the armatures point to the pole, the magnetic attraction holds the
armatures in that position with a considerable degree of force, the degree of force
will vary with the intensity of the magnetism produced by the magnet, and the
amount of force required to twist or rotate the axis carrying the armatures will be
an indication of the intensity of the magnetism produced by the magnet.
The invention is further described by the aid of the accompanying drawings,
Fig. 1, being a front view, and Figs. 2 & 3 end views of the instrument.
Five small bars of soft iron A, A, are attached to an axis B, which is free to
turn betwen the pivots C, C¹, carried by the end plates D, D¹, of the tubular case
or frame E, E, a cylindrical boss and a spiral spring F, are fastened to the axis at
the opposite end to that which carries the armatures.
The rear part of the pivot C¹, is made so as to act as a stud or fixed axis for a
toothed wheel G, which carries a disc H with a broad rim, a pinnion J, gears into
the toothed wheel and is actuated by the milled head J', on the outer side of the
end plate D¹.
From the disc H a short arm projects to which the outer end of the spiral spring
is fastened, the inner end being fastened to. the boss on the axis B. A scale is
formed on the broad rim of the disc H, a pointer is attached to the end plate D¹,
and another pointer is attached to the axis B, both pointers point to the zero of
the scale. An opening of considerable size is made in the tubular case E¹, so as to
allow of the scale and pointers to be easily seen.

page_text: In using the instrument the armature end is placed between the poles of the
magnet, with the armatures pointing towards the poles. The milled head is then
turned until the wheel G carrying the disc H, has drawn the the spiral spring
round until the strain so produced is just sufficient to overcome the action of the
magnetism upon the armatures. This is shewn by the pointer attached to the
axis B moving away from its normal position facing the fixed pointer attached to
the end plate D¹.
The scale on the broad rim of the disc H, is formed to shew the strain required
for different degrees of magnetic intensity, and is read off, or indicated by, the
fixed, pointer attached to the end plate D¹.
The divisions and figures of the scale are not shewn in the drawing.
Other methods of applying a strain to the axis carrying the armatures, and
other methods of indicating the strain may be adopted..
The armature is also capable of modifications,-magnetised bars of steel may be
- used in place of bars of soft iron, or the iron bars may be formed into electro-
magnets, excited by a current of known strength.
The tubular form of the case or frame work of the instrument, has been adopted
to permit the armature end being inserted into comparatively narrow spaces, but
other forms, or proportions, of the case or framework of the instrument may be
adopted.
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 intensity of magnetism produced by Magnets,
Electromagnets, or their equivalents, the essential part of which instrument
consists of an armature attached to an axis to which axis various degrees of
strain or force may be applied, substantially as described.