Improvements in Electrical Measuring Instruments.
Year: 1889

page_text: Date of Application, 21st Feb., 1889
Complete Specification Left, 21st Nov., 1889-Accepted, 11th Jan.. 1890
PROVISIONAL SPECIFICATION.
Improvements in Electrical Measuring Instruments.
WALTER HIBBERT 8 St. Dunstans Road, West Kensington S.W. London do
hereby declare the nature of this invention to be as follows:-
My instrument may be termed a permanent magnet inductor, or field measurer.
In electrical measurements, it is often necessary to obtain magneto-electric impulses
of known value. This is generally done by means of the earths magnetic field and a
coil of large area & many convolutions.
In my invention, permanent magnets are employed to produce a strong magnetic
field, so strong that one convolution of a small coil will give as great a magneto-electric
impulse as many turns of the large coil used in the earth inductor. This enables me
to arrange the convolutions so as to obtain a wide range of effect.
The magnetic system consists of a set of two or more hard steel magnets,
arranged so as to form a nearly closed magnetic circuit, the air space being not more
than about one sixteenth of an inch. With this special magnetic system, I provide a
framework on which is wound a number of convolutions of very thin insulated wire.
By means of suitable connecting studs and a switch, one or more of these con-
volutions can be put into action, as may best suit the exigencies of the measurements
to be made.
The framework and wire are so thin on one side that they can be thrust through
the air space between the permanent magnets. Or, as it is important to have as
narrow an air space as possible, the framework may be cut away from that particular
part of the wire which has to pass through. When one side of the coil passes in this
way through the air space, the coil encloses the magnetic field lines, & a transient
current will flow during the passage.
As, by conforming to the necessary conditions, the field can be made to include a
large number of lines in a small space, and as the number of wires on the frame can
be made to vary through a wide range, the instrument can be made to discharge
through any circuit a large variety of transient currents. The quantity of electricity
in these is known from the known constant value of the field, and the electrical
resistances of the circuit.
Dated this 21st day of February 1880
ᎳᎪᏞᎢᎬᎡ Ꮋ ᏴᏴᎬᎡᎢ.
COMPLETE SPECIFICATION.
Improvements in Electrical Measuring Instruments.
I, WALTER HIBBERT, of 8 St. Dundas Road, West Kensington, London, S.W.
Scientific Chemist, 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 :-
The instrument in accordance with my present Invention may be termed a
permanent magnet inductor or field measurer. In electrical measurements, it is
often necessary to obtain magneto-electric impulses of known value. This is
generally done by means of the earth's field and a coil of large area and many
convolutions.
Occasionally the impulses are obtained by the action of one coil (carrying an
electric current) on another.
In my Invention, permanent magnets are employed to produce a strong magnetic
field, so strong, that one convolution of a small coil will give as great a magneto-
electric impulse as many turns of the large coil used in the earth inductor.

page_text: This enables me to arrange the convolutions so as to obtain a wide range of
effect.
In order that my Invention may be the better understool I have appended
the accompanying three sheets of explanatory drawings, illustrative of my said
Invention, in which like letters of reference denote corresponding parts or members
in each.
The arrangement illustrated at Figures 1 to 4 is typical of an electrical measuring
instrument according to my Invention in its primary form wherein two permanent
magnets with a sliding induction coil are employed, Figure 1 being a side elevation
and Figure 2 a horizontal section on line A B; Figures 3 and showing detached
elevational views drawn to enlarged scale of the construction of the framework
and arrangement of convolutions of insulated wire thereon constituting the induction
coil hereinafter particularly described.
Figures 5 and 6 represent front and end elevational views respectively of the
measuring instrument arranged in a simplified form with one magnet only.
Figures 7 and 8 illustrate by sectional elevation and plan views respectively a
slightly modified form to that shown in the preceding Figures above referred to,
consisting of two hemispherical shells within which the magnet is disposed, the frame-
work on which the wire is wound-constituting the induction coil-sliding horizontally
on suitable slides or supports through the narrow air space or gap forined between
the edges of the divided sphere or circular shell aforesaid.
Figure 9 is a plan and Figures 10 and 11 elevational views, shown detached and
drawn to enlarged scale, of the induction coil or wire wound framework employed in
connection with the last above referred to construction.
Figures 12, 13, and 14, represent the form assumed by my improved electrical
measuring instrument when the construction is necessarily varied owing to the
alternative shape or arrangement given to the magnetic field or circuit.
It will be understood that constructions other than those shown in the drawings
may be employed without departing from the characteristic or principle features of
the Invention.
In every instance however a narrow gap or air space of tolerably large sectional
area is arranged in the magnetic field, within which, an induction coil is moved so as
to enclose a larger or smaller number of lines of magnetic force as desired, said
sliding coil being retained in the requisite positions in said gap between the pole
pieces either by friction as shown in Figures 1 to 6 and at Figure 12; by sliding
upon suitable supports or slides, Figures 7 to 11; or, by partially rotating on an axis,
Figures 13 and 14.
The magnetic system according to my Invention, in its primary form Figures 1 to 4,
consists of two steel magnets A A', let into the cast iron hole pieces B, B' as shown,
the adjacent faces of the latter approaching within about one sixteenth of an inch
from one another so as to leave an air gap or space there between thus forming a
nearly closed magnetic circuit or field. One of the faces marked n. n, of the pole
pieces B, B' will be a north pole; the other, marked s. s, will be a south pole;
the
poles of the magnets A, A¹ being denoted by the letters n, s.
To obtain constancy and also to obtain a maximum number of lines of magnetic
force it is as well not only to make this gap as narrow as possible but also to give it a
fair area.
Two zinc plates C, C, are secured by screws a to the projections on the
pole pieces B, B1, so as to retain the magnets A, A', in their sockets or recesses
formed in the pole pieces. Each of the magnets is magnetized in situ by means of
a coil of wire 1), D₁. These coils are slipped over the magnets and their adjacent
zinc plates, and may after magnetizing the field be removed if so desired. Care must
be taken to send the same current through both these magnetizing coils at the same
time, and to see that the magnets have their similar poles at the same side of the
instrument as shown. After passing a current of electricity through these magnetizing
coils for a minute or so, they may be removed, if thought desirable. The magnetic
system is now nearly ready. After a little time, varying with the arrangement and

page_text: the material, but usually not lasting more than a week or two, the field is practically
constant.
To obtain electro-magnetic impulses from the instrument constructed as above
described, I provide a sliding induction coil,-shown detached and enlarged at
Figures 3 and 4-that is to say a suitably constructed framework carrying a pre-
determined number of convolutions of insulated wire each series of convolutions being
of known value and having its ends connected to a pair of the terminals provided for
the purpose.
This sliding induction coil, which is of a thickness sufficient to allow of its passing
with friction and of its being retained, between the adjacent faces of the pole
pieces B, B', comprises, as shown, more particularly at Figures 3, and 4, a thin sheet
or sheets of vulcanite E.
Around a groove formed in the edge or between the edges of which latter is wound
a series of fine insulated wire W, of the required number of convolutions; the
convolutions or windings of the wire being calculated and divided into fractions of
known value, the terminals of each series being connected respectively to the binding
screws, b, b, in the ordinary manner. The movement of the sliding coil through the
gap is limited by stops c mounted on brass plates attached to the vulcanite frame-
work E, Figures 3 and 4, which meet the brass stops d screwed into the pole pieces, a
spring e attached to one or both of the pole pieces hearing against the framework in
order to further ensure that the latter shall work with friction between the faces of
the pole pieces.
Thus it will be seen, that with an apparatus constructed as above described it is
possible to put a known number of magnetic lines of force through any circuit by
simply connecting the terminals b, b. of the sliding coil with the circuit and pushing
the coil between the faces of the pole pieces.
In
Figures 5 and 6 show an instrument in which only one magnet is employed.
this arrangement the sliding coil is inserted and slides vertically between the opposing
faces of the pole pieces B, B', its travel being restricted by the stops c. d. and by the
brass plates f which latter is screwed in position beneath the adjacent faces of the pole
pieces.
In Figures 7 and 8 the steel magnet A is disposed centrally and preferably
vertically within the hemispherical shells B, B¹ constituting the cast iron pole pieces
of the magnetic system, said shells which are preferably, say half an inch in thickness
being suspended between the two standards. The ends n. s of the magnet A are
received within the projecting bosses formed on the inner surface of the shell
castings B, B', the magnet being retained in the position shown by the iron screw h.
inserted at the upper end of the shell.
The system is magnetized "in situ" by a coil D wound on the steel-rod or magnet A,
the ends of this coil being led through a small hole in the upper hemispherical
shell B, and connected to the terminals Figure 8. As in the preceding cases this
magnetizing coil may be dispensed with when the system has been once
magnetized.
In the last above described arrangement the induction or sliding coil which
passes through the air gap or space formed by the two hemispherical shells is
divided in two parts and is carried on a brass frame G moving on horizontal
slides or supports H attached to the standard. This sliding coil which is shown
in the plan view Figure 8 and in the detached enlarged views Figures 9, 10 and 11,
consists of vulcanite frame pieces E cut to the shape shown, a groove formed round
the three outer edges of which is arranged for the reception of the series of con-
volutions of fine insulated wire W, the remaining edge or side nearest the
hemispherical shells being cut away as shown so that the coiled wire on this side
is unsupported save only by the tension put upon same during winding. The ends
of the series of each of the two coils are connected to the binding screws shown
on the left side of the frame, being duly insulated from one another and the brass
of the frame. When the sliding frame just described is put in position on the
supports or slides H and secured by the adjustable screw block k so as to work

page_text: freely thereon Figure 10-the standards and supports. or slides: being shown in
section in this Figure-it can be pushed forward or backward. In the former
operation lines of force will be entering the nearer coil and be leaving the more
remote coil. By suitably joining the ends of the coils to any circuit these two
impulses produced can be added together or not as desired. The edges c; of the
vulcanite frame E come in contact with the standards F and so limit the motion of the
frame in both directions.
The arrangements shown Figures 12 to 14 represent in outline alternative forms
of the magnetic circuit, the details of construction being understood from the preceding
description.
In Figure 12, the magnetic system consists of a steel cylinder A divided or split
longitudinally; B, B¹, are the cast iron pole pieces having an air space therebetween,
D being the magnetizing coil, the whole being supported on suitable standards. The
sliding coil employed with this arrangement which would be similar to that described
in reference to Figures 1 to 6 enters between the two pole pieces as shown by the
arrow.
In Figure 13 A represents a bent steel magnet on which the magnetizing coil D is
wound, a second steel magnet A' lying between the ends of A being supported on the
standards F so that the poles of opposite names shall be near together. In this case
the inductor coil is pivoted at the centre j, the exposed portion of the wire W that
is the portion extending from one side of the frame to the other passing between the
opposing faces of the two magnets in the direction shown by the arrows.
Figure 14 represents an arrangement somewhat similar to that last described in
reference to Figure 13. The device here shown consists of an iron dumb bell or H
armature pivoted at its centre j so that it can partially rotate. A coil or coils is or
are wound on this armature in the well known manner so that the lines of magnetic
force of the field can be thrust through the coil or taken out by simply rotating the
armature through 90° or 180°.
The ends of the wound wire on this armature would be connected to their binding
screws attached to the supporting standards similar to Figure 13.
The strength of the field in the above instruments can be ascertained by methods
already understood and can then be used as a standard. When thus known any other
field can be measured by galvanometric comparison. Thus, the inductor coil of one
of the instruments is formed in a simple series circuit with a suitable galvanometer
and any other coil which can be made to enclose the lines in the field the strength of
which is to be ascertained. Now by taking an electro magnetic impulse first from
my inductor, and then from the other field, the relative values of the two are shown
by the elongation or "throw" of the galvanometer needle.
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 :
:
First In electrical measuring instruments the method of and means employed as
herein described, whereby permanent magnets in combination with sliding or partially
rotating induction coils are arranged in such a manner as to give electro magnetic
impulses of known value substantially as and for the purposes specified.
Second The improvements in electrical measuring instruments substantially as
herein described and shown from Figures 1 to 14 inclusive of the accompanying
drawings.
.
JAMES STEVENSON,
Gray's Inn Chambers, 20, High Holborn, W.C., Agent for Applicant.