Improvements in Electrical Measuring Instruments.
Year: 1890

page_text: Date of Application, 2nd Sept., 1890-Accepted, 4th Oct., 1890
COMPLETE SPECIFICATION.
Improvements in Electrical Measuring Instruments.
I, GEORGE WASHINGTON WALKER, of No. 50 Broadway, in the City, County
and State of New York, Inventor, do hereby declare the nature of my invention
for IMPROVEMENTS IN ELECTRICAL MEASURING INSTRUMENTS, and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :—
My improvements in electrical measuring instruments, relate more particularly to
the means for moving or vibrating the needle or other indicating portion thereof, and
has for its main object to provide a construction whereby the deflections or move-
ments of the indicating device may be proportional, or substantially so, to the
strength of the electric current employed, in order that an equally-divided or
graduated scale may be employed, and in order that uniform deflections and readings
may be obtained.
To this end and object my invention consists in the various features of construction
and combination of devices hereinafter more fully described and particularly pointed
out in the appended claims.
In the accompanying drawings,
Figure 1 is a front elevation partly in section of a meter embodying my
improvements.
Figure 2 is also a front elevation embodying a modification of my invention.
In the several views, the same part will be found designated by the same letter of
roference.
A, represents a solenoid magnet of arc-shape secured in position upon or against a
suitable support by means of screws a.
B, designates a circular core or armature provided with a radius-bar b, pivoted at c
centrally of the core and serving as the axis of motion of the core.
C₁
C, represents a needle or indicating means, secured at one end at the axis and
extending outward beyond the core.
D, designates an uru also secured at the axis c and threaded to receive a nut-like
weight E, by means of which the core may be balanced or adjusted to have the free
ond of the device C stand normally at the desired position; for instance, at the zero
or starting point of an ampere scale F.
The solenoid A is composed essentially of the curved non-magnetic tube d and
helix of insulated wire e, which is wound in a right handed direction about said tube,
and is included in the circuit whose current is to be measured or indicated. The
wire is so wound or arranged upon the tube or support as that the coil or helix tapers
or decreases in diameter from one end to the other, preferably in steps as shown.
The core is made of wire of comparatively small diameter, and of iron preferably
slightly harder than soft iron. It may however be made of soft iron or of steel.
The ends fund g of the core are preferably both arranged to stand within the coil
during the normal condition of the apparatus. The end g may however be arranged
to stand without the coil yet within the field of repulsion of the magnet. The end f
preferably stands within the coil for about one-half its length.
The scale F is arc-shaped and equally divided or graduated.
In the normal condition, the index or pointer rests at the extreme left or at zero.
During the passage of the current through the coil, the core is acted upon by the
magnetism developed, and is oscillated and the pointer vibrated along the scale to
stenneth of the current emploved

page_text: Owing to the variable or taper winding of the coil, the magnetism produced therein
decreases in the direction of the movement of the core, and the coro is influenced
directly as the strength of the current increases, moving equal distances in the coil
for each additional ampere of current or fraction thereof, and moving the index or
pointor correspondingly, thus making it possible to employ an equally-divided
scale.
Immediately the current is caused to pass through the coil the end is attracted
and drawn into the coil more or less according to the strength of the current and the
endy is repelled or drawn out or partially out of the coil.
By using a core or small diameter it may be saturated by a slight percentage of the
current used in the moter.
By using a small iron core which is harder than soft-iron, it may retain a small
amount of residual magnetism, which is of advantage.
Instead of having the end of the core arranged noriually within the coil, it may
be located exteriorly thereof, but I prefer to live”it near enough thereto to be within
the repellant influence of the magnet.
In lieu of having the ends fand g of the core wholly disconnected as shown, they
may be united to complete the ring by a piece of brass or other non-magnetic
substance, or the core may be made of brass faced or provided with a strip of iron or
steel.
The variable winding of the magnet is governed somewhat of course, by the weight E
which increases in power as the core and needlo advance and which acts upon the
same in a direction contrary to that in which said devices move undor the attractive
influence of the magnet.
The indicating devico C, may be made of plato-like form as shown at Figure 2,
perforated as ath to pass over a slot i, as shown in the Letters Patent of Great
Britain No. 11,341, dated July 15, 1889, to George Washington Walker and William
Bracken, whereby the deflections or movements of said device may be photographed
ns set forth in said patent. The scale F may be omitted in this construction. The
indicating device, like that shown at Figure 1, is adapted to move equal distances for
each unit of current, and hence uniform readings of the photographic record may be
obtained.
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. Tho combination of a curved solenoid magnat baving its coil tapering or of
varying diameter, a curved or circular pivoted core, and a needle or indicator.
2. The combination of a curved solenoid magnot having its coil tapering or of
varying dininoter, a curved or circular pivoted core, a needle or indicator, and a
counter-weight.
3. The combination of a curved solenoid magnet having its coil tapering or of
varying diameter, a curved or circular pivoted core, a needle or indicator, a counter-
weight, and a scale provided with equal divisions.
4. The combination of a curved solenoid magnet having its coil tapering or of
varying diameter, a curved or circular pivoted core of small diameter, and a noodle
or indicator.
5. The combination of a curved solenoid magnet having its coil tapering or of
varying diameter, a curved or circular pivoted core of small diameter and of a degree
of hardness greater than that of soft-iron and a needle or indicator.
6. The combination of a curved solenoid magnet having its coil tapering or of
varying diameter, a curved or circular pivoted core of small diamotor, a needle or
indicator, a counter-weight, and an equally-divided scale.
7. The combination of a curved solenoid magnot having its coil taporing or of
varying diameter, a needle or indicator, and a curved or circular pivoted coro having

page_text: one end well enclosed within the coil to be within its attractive influence, and the
other end also enclosed within the coil or near enough thereto to be within its repellant
influence.
Dated this 2nd day of September 1890.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.