Improvements in Electrical Measuring Instruments.
Year: 1896

page_text: Date of Application, 8th Aug., 1896
Complete Specification Left, 6th May, 1897-Accepted, 12th June, 1897
PROVISIONAL SPECIFICATION.
Improvements in Electrical Measuring Instruments.
I GEORGE KEITH BULLER ELPHINSTONE of 101 St. Martin's Lane London
Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
This invention is designed for the indication and recording by suitable means, of
intensities of current strengths and variations of electrical pressures. The instru-
ment consists of a magnetic system, which can either be made of permanent steel
magnets having suitably disposed pole pieces; or by means of an electro-magnet
suitably wound. Soft iron pole pieces are attached to the poles of the magnet system;
& threaded over one of these pole pieces a small coil moves in the space left
between them. This coil is attached to a light lever, which in turn is connected
to the axle and moving system of the instrument. Where the instrument is
required to be dead beat a continuous metallic circuit is used to form the frame
upon which such coil is wound. The axle which carries the indicating pointer or
arm carrying the recording pen, is suitably mounted between jewelled bearings in
a light frame; and either springs or a small weight may be used to oppose the
attracting force exerted between the magnet and the coil.
When the instrument is used for making records the arm is provided with a
pen or other suitable marking device, and this pen is preferably made in the
shape of a very light lever mounted on two little pivots, which while the arm
remains rigid allows of the point of the pen being in constant and equal
contact with the surface of the paper, in spite of variations of thickness and
surface of the latter. The paper may be moved under this recording pen by any
of the well-known methods, but prefer to use an arrangement consisting of a
toothed wheel having small pointed teeth, which engage in holes suitably punched
beforehand in a paper strip at regular intervals. These pins can be placed round
the periphery of a drum enclosing a clock; or they can be placed round the edge of
a wheel driven by a clock fixed to the frame work of the instrument; these pins
may be arranged at such intervals as to give points corresponding to any desired
interval of time.
By suitably winding the bobbins of the electro-magnet when such an
arrangement appears more advisable than the employment of a permanent magnet,
matters can so be arranged that the variation of current strength passing through
the wire round these coils, can be varied within very wide limits without causing
alteration in the intensity of the field between the poles to anything like a
corresponding extent. To secure this end, the space between the poles is kept
as small as possible so that the magnet system may be nearly saturated. The moving
coil has connected in series with it an idle resistance of suitable amount, and
this can be connected either in parallel with the coils on the electro magnet, or two
separate sources of electricity can be employed to supply current to them. As
an instance, when it is desired to use such an instrument for recording variations of
electrical pressure occurring at a considerable distance from the observing station; a
very small pair of pilot wires will be sufficient to supply enough current to the
moving coil, while the coils on the electro-magnet system are supplied from any
convenient source.
Dated this Seve
oust 1896
:

page_text: Improvements in Electrical Measuring Instruments.
I, GEORGE KEITH BULLER ELPHINSTONE of 101 St. Martin's Lane in the
County of London Electrical Engineer 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 object of this invention is to provide a reliable and satisfactory instrument
for the indicating and recording by suitable means intensities of current strength
and variation of electrical pressures and so arranging the constructional details as
to allow of the instrument being used at a considerable distance from the source of
current to be indicated or recorded by connecting the source with the indicating or
recording instrument by means of a small pair of pilot wires.
In the accompanying drawings the electromagnet system is shown in Figs. 4 & 5.
Fig. 4 is a front elevation, and Fig. 5 a plan. The magnetizing coil is wound
on the bobbins A and B. C represents the yoke of the magnet, and D
and E the limbs. F and G are the soft iron pole pieces. The pole piece G
has its end of a shape as shown at H (Fig. 4). This part H is embraced by the
moving coil K (Fig. 9).
Figs. 6 and 7 show the arrangement of a permanent magnet 20 (Figs. 6 and 7)
which may replace the electromagnet system in Figs. 4 and 5. The soft iron pole
pieces 22 and 23 (Figs. 6 and 7) inay be of the same shape as F and G (Figs. 4 and 5).
A plug 24 (Figs. 6 and 7) may be used as a back stop for the swinging coil K (Fig. 9).
The plug 24 can be removed and placed in the hole 25 (Figs. 6 and 7) clamping the
swinging coil K against the pin 26 (Figs. 6 and 7) for travelling purposes. The
same arrangement for clamping the coil K can be used in the electromagnet system
shown in Figs. 4 and 5.
The arrangements of the moving coil and axle are shown in Figs. 8, 9 and 12.
The moving coil K (Fig. 9) may be wound on a copper tube L, (Figs. 8 and 9)
of rectangular section. The ends of the copper tube I may be fixed to two
light levers M and N (Figs. 8 and 9). The other ends of the levers M and N
are screwed to the collar or sleeve P, (Figs. 8 and 9) which is rigidly fixed to the
staff or axle R (Figs. 8 and 9). To the collar P is fixed the balance weight W.
(Figs. 8 and 9), if a balance weight is used, or it may be operated by a spring
control. The axle R is supported by two bearings jewelled in the ordinary way.
Sections of these bearings are shown at I and J (Fig. 8). The bearings I and J
are screwed to the base O of the instrument (Figs. 2 and 3), and insulated from
the base and from one another. A spiral spring X (Figs. 8 and 12) has its inside
end rigidly fixed to the staff or axle R and insulated from the axle by the disc
of ivory or other insulating material. The outside end is fixed to an adjusting
lever V (Fig. 8), which is in metallic connection with the bearing I. The
lever U (Fig. 8) is in metallic connection with the inside end of the spring X. An
exactly similar spring is fixed on the other end of the axle R with its inside end in
metallic connection with the lever S and outside end in metallic connection with the
bearing J. The two ends of the coil K are connected by spirals of copper wire to
the levers U and S. The bearings I and J may be connected to the terminals of
the instrument.
It will thus be seen that there is a continuous metallic circuit between one
terminal of the instrument through the moving coil K to the other terminal of
- the instrument.
The collar P has a projecting pin Y (Figs. 8 and 9), to which an arm Z

page_text: (Figs. 8 and 10) of aluminium or other light material is attached.". To the
end of the arm Z (Fig. 10) is fixed a pen 2 (Figs. 10 and 11). The arrange
ments of the pen 2 are shown in Figs. 10 and 11. The pen 2 is fixed at its
upper end to a small axle 4, which drops into the slots in the small piece 3.
The piece 3 is pinned to the lower end.of.the arm. Z. The pen 2 thus rests
on the paper strip with a light, even pressure due to its weight, and is rigidly
fixed to the arm Z in the plane of the motion of the arm Z (and therefore of the
coil K)..
The paper strip 6 (Figs. 1 and 2) has at its right hand edge holes perforated a
certain equal distance apart. These holes slip over pius fixed on the circumference
of the drum or wheel 8 (Figs. 2 and 3).
The drum 8 is caused to revolve by the clock 9 (Figs. 2 and 3) at a regular rate.
The paper strip 6 is coiled round a spindle 10 (Figs. 2 and 3) which is easily
removable for renewing the strip 6. It will be seen that as the drum 8
revolves, the pins on its circumference engaging in the holes in the strip 6
will carry the strip along at a certain regular rate, and that the distance
between the holes will represent a definite time. The holes in the paper strip
can thus indicate time. After leaving the drum 8, the paper strip 6 passes
under fixed guides 11 and 12 and coils itself up in the lower part of the case of
the instrument.
To the lower part of the guides 11 and 12 is pivotted a brass piece 13 (Figs. 1, 2
and 3) which is held off the paper strip 6 by a spring 14 (Figs. 1, 2 and 3). When
the piece 13 is pressed down on to the strip 6 the strip can be torn across and the
piece in the lower part of the case removed for inspection.
By suitably winding the bobbins of the electromagnet the instrument can be
so arranged that the variation of current strength passing through the wire round
these coils can be varied within very wide limits without causing alteration
in the intensity of the field between the poles to anything like a corresponding
extent. To secure this end the space between the poles is kept as small as
possible so that the magnet system may be nearly saturated. The moving coil
has connected in series with it an idle resistance of suitable amount and this can
be connected either in parallel with the coils of the electro-magnet, or two sources
of electricity can be employed to supply current to them. For instance, when it is
desired to use such an instrument for indicating or recording variation of electrical
pressure occurring at a considerable distance from the observing station, a very
small pair of pilot wires will be sufficient to supply enough current to the moving
coils, while the coils on the electro-magnet system are supplied from any convenient
source.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electrical indicating or recording instrument the special form of pole
pieces and coil substantially as described and illustrated.
2. In an electrical indicating or recording instrument the arrangement of
levers, springs and balance weight or spring, substantially as described and
illustrated.
3. In an electrical indicating or recording instrument the combination of the
special form of pole pieces and coil with the arrangement of levers, springs and
balance weight or spring, substantially as described and illustrated.
4. In an electrical recording instrument the pen working on a hinge to insure
constant pressure on the paper substantially as described and illustrated.
5. In an electrical recording instrument the method of passing the paper by
means of wheel with pins engaging in perforations at definite distances or intervals
of time substantially as described and illustrated.
6. In an electrical indicating or recording instrument the use of two distinct

page_text: circuits having for its object the use of such instrument on long pilot wires
substantially as described.
7. An electrical indicating or recording instrument with its combination of parts
substantially as described and illustrated.
G. K. B. ELPHINSTONE.