An Improved Indicator for Electric Potentials.
Year: 1891

page_text: Date of Application, 20th Jan. 1891
Complete Specification Left, 20th Oct., 1c91-Accepted, 21st N.v., 1891
PROVISIONAL SPECIFICATION
An Improved Indicator for Electric Potentials.
I, Sir WILLIAM THOMSON, Professor of Natural Philosophy in the University
of Glasgow, in the County of Lanark, North Britain, do hereby declare the
nature of this invention to be as follows:-
This invention relates to an improvement on the well-known pair of repelling
balls or gold leaves, or the like, for showing a difference of electric potential. The
object of the invention is to provide a convenient instrument by which several
different prescribed potentials can be ascertained. In carrying out my invention I
use a pair of gold leaves, or preferably, a single narrow ribbon of gold leaf hung
by its middle over a metal bar and gummed or preferably clamped to keep it in
that position. To adjust it to proper sensibility through the desired range of
potentials I place below it a portion of a metal cylinder, not necessarily of circular
form. This cylindrical surface is so shaped as to cause by its inductive action on
the leaves the desired degrees of divergence for several different prescribed
potentials.
A divided scale is either engraved on the cylindric surface or on the front or
back of the containing case, or on both, so as to facilitate the reading of the
indications of the instrument and avoiding parallax due to the position of the eye...
The improvement also includes protecting-guards to prevent damage under the
influence of too high potential, and a protecting sheath to render the instrument
portable.
Dated this 19th day of January 1891.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.
COMPLETE SPECIFICATION.
An Improved Indicator for Electric Potentials.
I, Sir WILLIAM THOMSON, Professor of Natural Philosophy in the 'University
of Glasgow, in the County of Lanark, North Britain, 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 :-
My invention relates to an improvement in the well known pair of repelling balls
or gold leaves, or the like for showing a difference of electric potential. The
object of the invention is to provide a convenient instrument by which electric
potentials can be approximately measured. In carrying out my invention I use a
pair of gold leaves, or preferably, a single narrow ribbon of gold leaf hung on a
metal bar and gummed or clamped to keep it in that position. To adjust it to
proper sensibility through the desired range of potentials I place below it a portion
of a metal cylinder not necessarily of circular form. This cylindrical surface is so
shaped as to cause by its inductive action on the gold leaf the desired degrees of
divergence for different potentials.
A divided scale is either engraved on the cylindric surface or on the front or
back of the containing case, or on both, so as to facilitate the reading of the
indications of the instrument and avoid parallax due to the position of the eye.
The improvement also includes protecting guards to prevent damage under the
influence of too high potential, and a protecting sheath to render the instrument
portable.

page_text: In order that my invention may be properly understood and readily carried into
effect I have hereunto appended an explanatory sheet of drawing which I will
now proceed to describe.
Figure 1 is an elevation of the instrument.
Figure 2 is a separate view of the metal plate with gold leaf attached.
a a is a metal plate, to which is attached at bb, Figure 2, the gold leaf c c. The
metallic. plate is carried by a vulcanite piece dd, which is let into the case of the
instrument. The vulcanite piece carries a terminal e which is metallically con-
nected to the metal plate a a. A framework fff is hinged to the metal plate,
which can be opened out from the plate, as shown at Figure 1, when it forms a
protecting guard to prevent damage to the gold leaf under the influence of too high
potential, or it may be folded down, as shown at Figure 2, when it forms a
protecting shield to prevent damage to the gold leaf when the instrument is being
carried about. The surrounding case is made up of two flat sides 9 and h h, and
one cylindrical side i i, all made of metal, forming, with the back which is also of
metal, an electrical shield. The front is of glass. A divided scale jj is fixed to
the glass front, and another to the back of the instrument to facilitate the reading
of its indications and to avoid parallax due to the position of the eye. A terminal k
is fixed to the metal shield of the instrument. The two wires whose difference of
potential is required are brought to the terminals e and k. The gold leaf is then
repelled from the metal plate a, and the difference of potential is read off by means
of the scales on the back and front of the instrument.
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 !
claim is
The gold leaf electroscope substantially as described provided with a case part
of which is formed of a portion of a metal cylinder approximately perpendicular to
the plane of motion of the gold leaf acting electrically on the gold leaf by induction
and attraction, and having a protecting guard to prevent damage during use and to
form a protecting sheath for carriage.
Dated this 19th day of October 1891
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.