Improvements in Electric Measuring Instruments.
Year: 1893

page_text: Date of Application, 20th July, 1893-Accepted, 2nd Sept., 1893
COMPLETE SPECIFICATION.
[Communicated from abroad by ARAKELYAN HARRY ARMEN, of No. 15, City
Hall Square, Lynn, in the County of Essex and State of Massachusetts,
United States of America, Electrician.]
Improvements in Electric 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 object of this invention is to provide an improved instrument for measuring
the electro-motive force of electric currents, and to so arrange the graduated
index or gauge of such instrument that equal linear spaces thereon shall indicate
an equal number of volts as the oscillating hand or pointer traverses the face of
the gauge.
The first novel feature of the said instrument is the dial or face thereof having,
in contra-distinction to the ordinary graduation in the form of an arc of a circle, a
graduated index or gauge line subdivided into equal spaces and formed either in a
straight line or in a descending geometrical curve, drooping centrally toward the
axis of the pointer and being in any case a line other than the arc of a circle.
The shape of the instrument, is also novel and advantageous, having a flat
bottom or base and an horizontal projecting platform extending to the front and a
back at right angles thereto, so that it may stand firmly on any level surface or hang
against a vertical wall.
Another feature of the said invention consists in pivoting the pointer on an axis
at right angles to that of the coil, and connecting it with an armature of iron or
steel counterbalanced and working within the coil while the pointer projects
therefrom and traverses the face of the index plate. In some cases, I combine
with the flattened spool, enclosed iron or steel piece, and pointer, a magnet
external to the coil and acting through the same on the armature and pointer.
In the accompanying drawings,
Figures 1 and 2 are front and side elevations respectively of one form of the
improved instrument.
Figure 3 is a front view with the front plate removed, showing the interior.
Figure 4 is a sectional plan shewing the flattened spool and coil and the
counterbalanced piece to which the pointer is connected.
Figure 5 is a front view showing a modification of the apparatus, in which the
pointer works horizontally, a part of the front being represented as removed, and
showing the straight index line.
Figure 6 is an underside view of the flattened coil and magnet shown in
Figures 5 and 7 and
Figure 7 is a modification similar to that shown in Figure 5 but with the index
arranged horizontally.
The case A of the instrument, Figures 1, 2, 3 and 4, has a flat bottom with a
base or foot a projecting in front, and a flat vertical back as seen in Figure 2 so
that it will stand steadily on a level surface or fit firmly against a wall. The
front plate B is made removable, in order to give access to the armature K,
the coil C and other interior parts, as shown in Fig. 3. The upper portion 6 of the
plate B seen in Figure 1, is shown distinct from the lower portion, leaving an open
space between them showing a part of the dial D and the graduated index
peculiar to the said invention formed thereon.

page_text: The index or gauge line E which characterizes the said instrument, is shown in
Figures 1 and 3 and is formed in a descending geometrical curve, such as a
parabola or hyperbola, and being a line other than the arc of a circle drooping
toward the axis of the pointer F. This parabolic curved line E is graduated in
equal subdivisions, and the hand or pointer F traverses the face of the dial as it is
actuated by the current through the coil C.
In the use of this instrument, the armature K and its counter-balance k moving
with the pointer F come gradually nearer to the middle of the coil C, and the
attraction varies with the square of the distance in accordance with the well
known law. The pointer traversing unequal distances when the index or gauge is
in the form of an ascending arc of a circle, but with my descending index line it
moves over equal spaces by equal increments of electricity.
In the form of instrument shown in Figures 5, 6 and 7, a magnet M, external to
the coil C is provided, and connected to the axis of the pointer F is a steel
needle N which is influenced by the attraction of magnet M and which tends to
keep the pointer at the zero point, acting thus somewhat after the nature of a
spring. The electric current through the coil C causes the pointer to traverse the
face of the dial, the index indicating the force of this current.
The straight index line O, represented in Figures 5 and 7, is employed in cases
where the magnet M is used in place of a weight or spring to restore the pointer
to its normal position.
I do not limit myself to the exact construction of the instruments as herein
shown, since it is obvious that the index lines as described may be employed on
instruments differing in their mechanical details, and also on ammeters.
Having now particularly described and ascertained the nature of the said inven-
tion 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. In a volt meter, the hand or pointer F actuated by the electric current, in
combination with a dial having an index or gauge line formed thereon as described,
such line being other than the arc of a circle and graduated in equal subdivisions,
substantially as set forth.
2. In a volt meter, the case A, having a flat back and bottom, and a face
plate B partially covering the front thereof, in combination with the armature
and eccentrically mounted pointer and a drooping parabolic index or gauge,
substantially as set forth.
3. In an instrument for measuring electric currents, a coil through which the
current passes, and a pointer pivoted on an axis at right angles to the axis of said
coil, in combination with an armature connected to said pointer and working
within said coil while the pointer traverses the face of the dial, substantially as
set forth.
4. In an instrument for measuring electric currents, a coil through which the
current passes, and a magnet, external thereto, in combination with a vibrating
pointer connected at its pivot with a needle influenced by said magnet, and with a
straight index line graduated to denote the force or intensity of the electric
current, substantially as set forth.
Dated this 20th day of July 1893
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.