IMPROVEMENTS IN ELECTRIC MEASURING, RECORDING, AND REGULATING APPARATUS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Stephen Henry Emmens at the Office
of the Commissioners of Patents on the 25th August 1882.
STEPHEN HENRY EMMENS, of Argyll-Street, in the County of Middlesex,
Actuary, "IMPROVEMENTS IN ELECTRIC MEASURING, RECORDING, AND REGULATING
APPARATUS,"
My invention relates to apparatus designed to measure the quantity and intensity
of an electric current, and the resistance of a circuit, for recording the quantity of
electricity traversing a circuit, and for regulating the production of an electric
current in proportion to the resistance to be overcome.
My apparatus consists essentially of two solenoids, the movable cores of which
are attached to a centrally pivotted crossbar. A needle or indicator upon this
crossbar indicates upon a suitably graduated dial, any relative change of position
of the two solenoid cores.
I make the two solenoids of unequal magnetic capacity and electrical resistance,
and I so arrange the terminals that the coils can be joined up in short circuit or
can be connected by any desired intermediate circuit. I further attach suitable
springs to keep the free extremities of the cores at the medium planes of the
solenoids when the standard current is passing.
The operation of my apparatus depends mainly upon two factors viz:-the
strength of the current, and the fall of potential between the points at which the
current respectively enters and leaves. This causes a differential variation in the
magnetic powers of the two solenoids and a corresponding and proportional
movement of the indicator actuated by their moving cores. I prefer to adjust the
capacities of the two solenoids, so that the indicator shall be normal when a
standard current of one ampére traverses a circuit of one thin resistance between
the solenoids; but it is obvious that no particular normal position is essential.
This apparatus may be used as an ohm meter, as an amperometer, as a volt
meter, as an electric supply meter, and as an electro regulator.
For use as an ohm meter I graduate, by interposing standard resistance coils
between the solenoids and marking off the various portions by the indicator when
a current is passed through the successive resistances.
For use as an amperometer I short circuit, and mark off the various positions by
the indicator, when currents of known quantities are successively passed through.

page_text: For use as a volt meter I determine the resistance when in short circuit and
mark off the ampére with the corresponding number of volts.
For use as an electric supply meter I interpose the service circuit between the
solenoids and fit the indicator with a pencil, or other suitable working instrument,
to mark on a tape caused to advance at a regular speed by clockwork actuated by
the working current. A record is thus made of the time during which the current
is flowing and of the work performed by it
For use as an electro regulator, I interpose the service circuit between the
solenoids, and by suitable means connect any part of the cross bar or moving parts
with the governing gear of the engine or generator.
This connection is so arranged that any differential movement of the solenoid
cores causes an increase or diminution of the electric supply proportionate to the
increased or diminished resistance of the circuit.