Improvements in Electrical Measuring Instruments.
Year: 1891

page_text: Date of Application, 13th Jan., 1891-Accepted, 14th Feb., 1891
[Communicated from abroad by EDWARD WESTON, of Newark, New Jersey,
United States of America.]
Improvements in Electrical Measuring Instruments.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45, Southampton Buildings, in the County of Middlesex, 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 invention relates to an electrical measuring instrument more particularly
intended for use in measuring difference of potential between terminals of an electric
circuit.
The accompanying drawings show four modifications of the said instrument, the
essential features in all being the same but with certain differences in construction
hereinafter to be pointed out.
Figs. 1 and 2 illustrate the first form in which Fig. 1 is a vertical section on the
line XX of Fig. 2, and Fig. 2 is a plan view.
Figs. 3 and 4 illustrate the second form in which Fig. 3 is a vertical section and
Fig. 4 a plan view on the line X X of Fig. 3.
Fig. 5 is a vertical section of the instrument of the third form.
Figs. 6, 7, 8 and 9 illustrate the fourth form, and in said figures, Fig. 6 is a face
view, Fig. 7 a diagram illustrating the arrangement of the coils, Fig. 8 a vertical
section on the line X X of Fig. 6 and Fig. 9 a detail view showing the mode of
attachment of the spiral springs to the movable coil.
In all of said figures similar numbers and letters of reference indicate like
parts.
Referring first to Figs. 1 and 2, A. is a base board, B the enclosing case of
the instrument, C a permanent magnet having four bent radial arms which receive
the flanged ring or pole piece D. E is a cylinder of magnetic material secured to
said magnet and forming the other pole piece. The cylinder D and ring G are
concentric, and there is, therefore, an annular space between them in which there
is a very intense magnetic field. G is a grooved ring of copper or other diamagnetic
material, upon which is wound a coil of insulated wire. Said ring is disposed in
the annular space between the poles of the magnet, and is provided with a bail H
to which is attached the short rod I. Rod I is secured to the lower end of a spiral
spring J, which spring is fastened to a short rod K attached to the fixed arm L.
The rod I passes freely through the scale plate M of the instrument, and carries
an index or pointer N which moves over said scale plate. The scale plate is
suitably marked to indicate units of electrical pressure. The coil or ring G is
connected in circuit with the binding posts 1 and 2. When a current circulates
through the coil said coil tends to move bodily in the annular space between the
poles of the magnet, and is caused to travel over a distance bearing a relation to
the difference of potential between the binding posts 1 and 2. As said coil moves
it also rotates by reason of the construction of the suspending spring J; and as it
rotates it moves the needle N over the scale. The scale being marked suitably as
above described, the extent of movement of the coil will be shown on said scale and
translated into suitable units of electrical pressure.
Referring now to Figs. 3 and 4, 1 is a circular case forming the base of the
instrument and containing the scale-plate 2 which is visible through a glass covered
opening 3 in the cover 4. 5 is a cylindrical case provided with a head 6 to which,
by the tubular screw bolt 7, is secured a core 8. Also secured to said case is a
ring 9. The ring 9, case 5, cover 6 and core 8 constitute a magnet in which the
ring 9 and core 8 are the pole pieces. Between said pole pieces there is an annular

page_text: magnetic field. Surrounding the core 8 is a spool 10 of non-magnetic material
which carries a coil 11 of insulated wire. In the annular field between the pole
pieces is disposed a ring 12 of brass or other non-magnetic material closed on its
lower side by a diaphragm 13. Extending through the core 8 is an axial opening
in which is disposed a spiral spring 14. This spring is connected at its upper end
to a threaded rod 15. which passes through a Hanged sleeve 16 supported in the
hollow bolt 7, and is secured in place by a nut 17. The spring is connected to a
rod 18 which is fastened to a pin 19 secured at the centre of the diaphragm 13. In
the lower portion of the opening extending through the core 8, is a flanged sleeve 20
having partitions 21 and 22 provided with jewels through which the rod 18 passes.
In this way transverse motion of the suspension device is prevented. The index
needle 23 is suspended from the lower side of the diaphragm 13, extends over the
scale 2, and is held in a horizontal position by a spring 24. Surrounding the ring 12
is a coil 25 of insulated wire which is connected in series with the coil 11. When a
current passes through the coils, its effect in accordance with well-known laws, is
to cause the coil 25, and hence its supporting ring 12 to be moved longitudinally
upward or downward in the annular space between the pole pieces. The ring 12 at
the same time is caused to rotate by the action of the spring 14. The extent of
rotation is proportional to, and hence measures, the movement of said ring, and this
movement has a relation to the magnetic force due to the difference of potential
between terminals at which the current, enters and leaves the instrument. The
rotation of the ring causes the needle 23 to move over the scale 2 which is suitably
marked.
Referring next to the form shown in Fig. 5, the lower case or standard of the
instrument is here shown enlarged and the vertical case 5 is set for some distance
into it. The rod 18 as in Figs. 3 and 4, enters the opening in the core and passes
through jewelled bearings 21 and 22. To the diaphragm 13 is pivoted a link 26
communicating with a bell crank lever 27 pivoted to fulcrum 28. Bell crank
lever 27 carries a forked piece 29 to which is attached spiral spring 14.
The other
end of the spiral spring is fastened to a short threaded rod 29* which is received in
the collar 30. Another spiral spring 14* is provided with a threaded rod 31
entering collar 30; and at its opposite end is fastened to a rod 32 which is secured
by nut 33. The needle 34 is supported on collar 30 and is counterweighted at 35.
It extends through an opening in cover 4 and between the two plates of glass 36
and 37 secured in a circular frame 35. On one of these plates as 37, is inscribed a
scale marking. Resting on the cover of the instrument, is an incandescent electric
lamp 36 connected with any independent source of electricity. When a current
is passed through the coils 11 and 25, motion of the ring 12 occurs, in the direction
of its axis, and this motion is transmitted through the link 26 and bell crank
lever 27 to the springs 14, 14*. These springs rotate the sleeve 30 and so causes
the needle 34 to move over the scale, and to indicate the difference of potential
between the terminals of the instrument. The object of the electric lamp 36* is to
cause light to be transmitted through the glass scale-plates, so that the indication
of the instrument may be read at a considerable distance. One of the glass plates
may be clear and the other partly opaque or semitranslucent.
Referring now to Figs. 6, 7, 8 and 9, 38 is the case of the instrument having
heads 39 and 40 of magnetic material. These heads support pole pieces 41, 42.
Surrounding said pole pieces within the case is a ring 43. The pole pieces 41 and 42
are of like magnetism and the ring 43 of opposite magnetism. Supported on spools
upon the pole pieces 41 and 42, are coils 44, 45 of insulated wire. Surrounding the
extremities of both pole pieces 41 and 42 and disposed in the annular space between
said pole pieces and the ring 43, is a ring of brass or other noninductive material
around which is wonnd a coil 47 of fine wire. The ring 46 is supported by spiral
springs 48 and 49, which springs have at each extremity threaded rods, as 50, 51.
Extending across the ring 46 is a diaphragm 52 having a central aperture which
receives a projection 53 on the flanged boss 54. The threaded extremity 50 of the
spring 48 enters said boss on one side of said diaphragm. The boss 54 is secured

page_text: in place by the collar 55 and nut 56 which is received on the threaded end 51 of
spring 49.
Passing through the heads 39 and 40 are hollow screw bolts 57 and 58, each
having a bushing 59, 60, which receive the threaded rods 61 and 62. By setting
up. the nut 63 which secures said rods, more or less, the diaphragm 52 may be
adjusted midway between the pole pieces 41 and 42, and the springs regulated.
The outer ends of the springs are covered by caps 64. On the case 38 is a frame 65
containing glass plates 66 and 67, on one of which is inscribed a scale marking, as
already described in connection with the instrument shown in Figs. 3, 4, 5. The index
needle is fastened to the ring 46 and moves over the scale, and the case 38 is supported
on a standard 69. Fig. 7 illustrates the circuit connections in the instrument.
The circuit proceeds by wire a from one terminal through the coil 45, by wire b
to spiral spring 49, to the coil 47 on ring 46, spring 48, wire c, fixed coil 44 and
finally by wire d to the other terminal. As the poles 41 and 42 are of like name,
it follows that the ring 46 will be moved bodily in the manner already described
in connection with the preceding forms of instrument, and also given a rotary motion
by the springs 48 and 49 so as to cause a movement of the needle 68 over the
scale; and in the manner already described, the extent of rotation of the coil, and
hence difference of potential between the terminals of the instrument will be thus
visually indicated.
Having now fully ascertained the nature of the said invention and in what manner
the same is to be performed, as communicated to me by my foreign correspondent,
I declare that what I claim is:-
1. An electrical measuring instrument embodying a magnet having one pole
surrounding the other, provided with a coil disposed in the annular space between
said poles and supported so as to move axially and also to rotate on its axis on the
establishment of the current; and with a device for indicating the extent of rotation
of the said coil.
2. An electrical measuring instrument embodying a movable coil and a fixed
coil in circuit having their axes in prolongation, and disposed in inductive
proximity, the movable coil being axially movable and also rotary on its axis on
the establishment of the current, and a device for indicating the extent of rotation
of said movable coil.
3. An electrical measuring instrument embodying two fixed coils and a movable
coil in circuit having their axes in prolongation and disposed in inductive proximity,
the movable coil being supported between the fixed coils so as to be axially movable
and also rotary on its axis on the establishment of the current, and a device for
indicating the extent of rotation of said movable coil.
4. An electrical measuring instrument embodying an electro magnet having its
coil in circuit with an axially movable rotary coil surrounding its core and provided
with a device for guiding said coil in its axial movement and also a device for
indicating the extent of rotation of said rotary coil.
5. An electrical measuring instrument embodying two electro magnets having
like polar ends of their coils facing and having their coils in circuit with an axially
movable rotary coil surrounding.said polar ends and itself surrounded by a ring
pole common to both magnets, and a device for indicating the extent of rotation of
said rotary coil.
Dated this 12th den of Ian 1801
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.