MEASURING AND RECORDING QUANTITY OF ELECTRICITY AND IN THE MEANS
Year: 1882

page_text: LETTERS PATENT to John Hopkinson, of Westminster Chambers, in the
IMPROVEMENTS IN
County of Middlesex, F.R.S., for an Invention of
MEASURING AND RECORDING QUANTITY OF ELECTRICITY AND IN THE MEANS
PROVISIONAL SPECIFICATION left by the said John Hopkinson at the
Office of the Commissioners of Patents on the 4th January 1882.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN MEASURING AND RECORDING QUANTITY OF ELECTRICITY AND
IN THE MEANS OR APPARATUS EMPLOYED THEREFOR."
My Improvements relate to methods of measuring the whole quantity of electricity
which passes through a conductor. For this purpose I make use of a centrifugal
governor or centrifugal apparatus and control its velocity by electrical or electro
magnetic apparatus. The centrifugal force of the governor may be opposed by the
attraction or repulsion of one conductor conveying electricity on another conductor
conveying electricity, of an electro-magnet for its armature or of a solenoid for its
corc. Or the centrifugal force may move one contact piece or its equivalent and
the electrical apparatus a second contact piece in such wise that as the speed of tho
governor increases the former piece or its equivalent is moved from the second
whilst as the electrical force increases the second piece follows up the first. When
the centrifugal force is mechanically opposed to the electrical force the governor
may act by bringing a friction brake into action or it may act by making and
breaking an electrical contact. The govornor may be driven by a small dynamo-
electric machine or in the case of using a brake the governor may be driven by
clockwork. In order to prevent the force due to the electro-magnet or its equivalent
from putting undue pressure on the bearings of the centrifugal governor I find it
advantageous to arrange the electro-magnet symmetrically about the axis of the
governor. When the governor and electro-magnet or its equivalent carry electrical
contact pieces the ordinary mechanism of the governor may be replaced by a heavy
fluid such as mercury the surface of the mercury being one of the moveable contacts.
The electro-magnet or its equivalent wire may either carry the whole current to be
measured or may be a shunt carrying part only of that current. The number of
revolutions of the governor may be counted and recorded by clock work or other
suitable mechanism,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Hopkinson in the Great Seal Patent Office on the 4th July
1882.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN MEASURING AND RECORDING QUANTITY OF ELECTRICITY AND
IN THE MEANS OR APPARATUS EMPLOYED THEREFOR."
core.
My improvements relate to methods of measuring the whole quantity of electricity
which passes through a conductor. For this purpose I make use of a centrifugal
governor or centrifugal apparatus and control its velocity by electrical or electro-
magnetic apparatus. The centrifugal force of the governor may be opposed by the
attraction or repulsion of one conductor conveying electricity on another conductor
conveying electricity of an electro-magnet for its armature or of a solenoid for its
Or the centrifugal force may move one contact piece or its equivalent and
the electrical apparatus a second contact piece in such wise that as the speed of the
governor increases the former piece or its equivalent is moved from the second;
whilst, as the electrical force increases the second piece follows up the first. When
the centrifugal force is mechanically opposed to the electrical force, the governor may
act by bringing a friction brake into action or it may act by making and breaking
an electrical contact. The governor may be driven by a small dynamo-electric
machine or in the case of using a brake the governor may be driven by clockwork.
In order to prevent the force due to the electro-magnet, or its equivalent from
putting undue pressure on the bearings of the centrifugal governor I find it
advantageous to arrange the electro magnet symmetrically about the axis of the
governor. When the governor and electro-magnet or its equivalent carry electrical
contact pieces the ordinary mechanism of the governor may be replaced by a heavy
fluid such as mercury the surface of the mercury being one of the moveable contacts.
The electro-magnet or its equivalent wire may either carry the whole current to
be measured or may be a shunt carrying part only of that current. The number
of revolutions of the governor may be counted and recorded by clockwork or other
suitable mechanism.
And in order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several Figures on the annexed Sheet of Drawings the same letters of reference
indicating corresponding parts in all the Figures.
Figures 1, 2, 3 and 4 show one arrangement of current meter constructed
according to my Invention. Figure 1 being a side elevation, Figure 2 a front
elevation, Figure 3 a back elevation with part in section and Figure 4 a sectional
plan.
a a are the magnets of a small dynamo-electric machine to be used as a motor;
bis the armature of the same. This dynamo-electric machine is arranged with fine
wire as a shunt to the current to be measured; this derived current passes first
round the electro-magnets aa then by the brush e to the armature thence by the
brushes and c to the insulated ring f through the wire g (see Figure 3) to an
insulated ring here the circuit may be either made or broken according as the
moveable piece or core i is lowered or raised if this piece be lowered the circuit is
thus completed to the metal work of the instrument; jis a coil of wire through
which the current to be measured passes it is surrounded by an iron tube / sup-
ported by the frame of the instrument; / is a shaft driven by the electro-motor,
carrying an iron core m fixed to the shaft; n n are governor balls which by levers
and links o o raise or tend to raise the iron core i which revolves with the shaft /

page_text: and can slide upon it the revolutions of the shaft are counted by means of the
worm and worm wheel q the pinions and wheels and the dials s; springs t
take the weight of the core i and are so adjusted that when no current passes
through the coil j contact is broken with the insulated ring but that a very sinall
current through this coil will make the contact and cause the electro-motor to
begin to revolve. When a current passes through the coil j it causes attraction
between the fixed tube and the flanges of the moving cores m and i also between
the cores m and i the magnetic force upon i is vertically downwards and is pro-
portional within limits to the square of the current in the coil.
When the governor
is revolving the centrifugal force on the governor balls is proportional to the square
of the speed of revolution and tends to lift the core i in opposition to the magnetic
force. These forces will exactly balance one another for if the speed be too great
the circuit of the electro-motor will be broken and the speed will fall if it be too
small the electro-motor will work and the speed will increase. The result is that
the system will revolve with a velocity proportional to the current through the
coil. It will be remarked that owing to the symmetrical arrangement of the cores
the electro-magnetic forces are balanced so far as the shaft is concerned and that
they do not tend to put any pressure upon the bearings.
Figure 5 shows another arrangement of the controlling mechanism: the coil j
tube and cores m and i may be the same as before, so also may the governor ;
but as in all the apparatus various forms of governor may be employed, a different
form is shown in Figure 5 the system is driven by suitable clockwork and the
speed is controlled by the flange of the core i coming in contact when it rises with
the brake screws u u instead of by breaking an electric circuit.
Figure shows a modified arrangement of governor and electro-magnet the
object being to get rid of all joints and sliding surfaces of the mechanism. The
iron pieces vv are suspended by springs ww and are attracted in opposition to
centrifugal force by the core i which in this case is fixed to the shaft. The circuit
of a driving electro-motor is made or broken at xx.
Instead of balancing centrifugal force against electro-magnetic force the centri-
fugal force may move one contact piece or its equivalent and the electrical apparatus
a second contact piece so that as the speed of the governor increases the former is
moved from the latter whilst as the electrical force increases the latter follows up
the former. This may be done in several ways one is shown in Figures 7 and 8.
A is a vertical shaft driven by a suitable electro-motor and carrying three or more
vertical tubes B B and C connected with each other, and containing mercury; D is
a contact piece making contact with the mercury unless the mercury is caused to
descend in the tube C by the action of centrifugal force; E is a fixed coil of wire
through which the current to be measured passes; F is a moveable coil carrying by
an arm the contact piece D; the current to be measured also passes through F.
The passage of the current causes the coil F' to turn on its bearings G G and to
depress the contact piece D by a distance proportional to the square of the current.
The centrifugal force on the other hand depresses the surface of the mercury in the
tube C to an extent proportional to the square of the speed. The revolutions of
shaft A may be counted by any suitable mechanism.
Having now described and particularly ascertained the nature of my said Inven-
tion and the manner in which the same is or may be used or carried into effect I
would observe in conclusion that I do not limit myself to the precise details
illustrated in the accompanying Drawings as the same may be varied without
departing from the nature of my Invention, but what I claim is :-
First: In an electric measuring apparatus the use of a centrifugal governor
the speed of which is electro-magnetically controlled substantially as hereinbefore
described with reference to the accompanying Drawings.
Second-In an electric measuring apparatus the use of a centrifugal governor
in which the centrifugal force is mechanically opposed by the attraction or repulsion
of an electro-magnet or of one conducting wire for another conducting wire
substantially as described with reference to the accompanying Drawings.

page_text: Third In an electric measuring apparatus the combination of the centrifugal
governor and a dynamo-electric machine, the circuit of which is opened or closed by
the action of the governor substantially as hereinbefore described with reference to
the accompanying Drawings.
Fourth In an electric measuring apparatus the arrangement of magnet and
governor for the purpose of avoiding pressure on the bearing substantially as
herein before described and illustrated in Figures 1 to 6 of the accompanying
Drawings.
Fifth In an electric measuring apparatus the use of a mercurial or other fluid
governor in combination with an electro-magnetic arrangement substantially as
hereinbefore described with reference to Figures 7 and 8 of the accompanying
Drawings.
In witness whereof I the said John Hopkinson have to this my Specification
set my hand and seal this Sixteenth day of June One thousand eight
hundred and eighty two,
JOHN HOPKINSON. (L.S.)