Improvements in Apparatus for Measuring Electric Currents.
Year: 1885

page_text: :
Improvements in Apparatus for Measuring Electric Currents.
1
A...
ROBERT DANIEL SMILLIE Electrical Engineer, residing at 139 West Bridge End
Dumbarton I do hereby declare the nature of my Invention for THE MEASURE-
MENT OF ELECTRIC CURRENTS to be as follows:-
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Improvements in apparatus for measuring electric currents whither of the
continuous, alternating or interrupted kind, free from induction errors, by means
of the curvature produced on a metalic bar, rod, or ribbond having a slight initial
curvature and bearing between two ridgid supports, when expanded by the heat
generated by a current passing through the said bar, rod or ribbon. The variation
of curvature due to the variation of current being communicated to the index by a
system of levers, wheels, pullies, or a barrel with cord. or chain, or combinations
thereof.
"
.
此
The frame or bed-plate being made of metal having, a similar co-efficient of
expansion to the said bar rod or ribbon in order to compensate the error due to
variation of atmospheric temperature...
..

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Measuring Electric Currents."
ROBERT DANIEL SMILLIE, Electrical Engineer residing at 139 West Bridge End
Dumbarton I do hereby declare the nature of my invention for MEASUREMENT
OF ELECTRIC CURRENTS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
I propose to utilise the curvature produced on a metalic conductor of bar, rod or
ribbon form, which is expanded by heat due to an electric current being passed
through it when its ends are bearing against, pivoted on, or fastened to ridgid
supports, but free to move latterally between those supports; a slight initial
curvature being, given to the said metalic conductor in the direction in which it is
intended to move.
:
The metalic conductor on being heated by the current will have a leaneal
expansion but not being free to move in the direction of its length will be forced
to assume a curved form.
This curvature, will of necessity, vary with the temperature of the conductor and
the temperature will vary with the quantity of current; consequently the curvature
produced will be a measure of the current.
This heating effect is produced alike with alternating, continuous or intermittent
currents and it is therefor suitable to be used with either..
To correct for variations of atmospheric temperature in a simple form of the
instrument, the ridgid supports, which in this case may be made of a non-conducting
body such as slate, are carried on a bed-plate constructed of metal of a similar
expansibility to that of the metalic conductor.
The instrument is placed in circuit through two flexible conductors which are
Becured to the metalic conductor.
In that point of the metalic conductor where the greatest movement takes place
is fixed an insulated stud to which is secured a light chain which takes a turn
round a small drum revolving on pivots, to one end of which is fixed an index;
and a recoil spring is also fixed to the drum or pivot which serves to recover the
index and keep the chain taut against the pull of the curved metalic conductor.
In Figs. Nos. 1 & 2 the following are the reference letters to the various parts.
A Metalic Conductor.
B Base Plate

page_text: Having now particularly described and ascertained the nature of any said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
An improved instrument for the measuring of currents of electricity, in which a
current of electricity heats a conductor fixed between two ridgid supports and
causes it to assume a curved form greater or less according to the quantity of
current flowing through the said conductor and this curving of the conductor in
turn causes movement of an index as substantially described.
Dated this twenty ninth day of September 1886.