IMPROVEMENTS IN CONTRIVANCES FOR REGISTERING THE AMOUNT OF WORK GIVEN ELECTRICALLY TO ANY PART OF AN ELECTRIC CIRCUIT IN A GIVEN TIME
Year: 1882

page_text: ETTERS PATENT to William Edward Ayrton, Professor of Technical Physics
Fellow of the Royal Society, and John Perry Professor of Mechanical
Engineering and Applied Mathematics in the City & Guilds of London
Technical College Finsbury in the county of Middlesex for an invention
of IMPROVEMENTS IN CONTRIVANCES FOR REGISTERING THE AMOUNT OF
WORK GIVEN ELECTRICALLY TO ANY PART OF AN ELECTRIC CIRCUIT IN A
GIVEN TIME
PROVISIONAL SPECIFICATION left by the said William Edward Ayrton and
John Perry at the Office of the Commissioners of Patents on the 5th June
1882.
WILLIAM EDWARD AYRTON Professor of Technical Physics Fellow of the Royal
Society, and JOHN PERRY Professor of Mechanical Engineering & Applied
Mathematics in the City & Guilds of London Technical College Finsbury in
the County of Middlesex IMPROVEMENTS IN CONTRIVANCES FOR REGISTERING
THE AMOUNT OF WORK GIVEN ELECTRICALLY TO ANY PART OF AN
CIRCUIT IN A GIVEN TIME.
ELECTRIC
To measure Electrical energy given to a house or to any Motor or Lamp or other
contrivance during a given time it is at present necessary to use such an Instrument
as our Voltmeter to measure the difference of potential existing at any instant
between the two extremities of the portion of a circuit in which the expenditure
of energy occurs; at the same instant to measure with such an Instrument as our
Ammeter the current flowing. The product of these measurements multiplied by
a certain constant number gives the horse-power which is at that instant being
given electrically to the circuit; or the horse-power being expended at any moment
may be measured by an Instrument like our Electric Powermeter. If these
operations are repeated at equal intervals of time it is possible to calculate
approximately the electric energy given to the circuit during any time.

page_text: Our present invention is an Instrument which continually performs this
operation and shows by pointers on dials the total amount of energy which has
passed electrically into a circuit since any previous date. It consists of a small
machine shaped like a Dynamo Electric Machine. The movable armature of this
machine is wound with moderately thick wire. The fixed magnets are wound with
a wire whose resistance may be more than Two hundred ohms, or again the
moving part may have a conciderable resistance, and the fixed may have the
smaller resistance. The cores in both cases may be of very soft iron or other
magnetic matter, or they may be of nonmagnetic matter, so that they cannot
be come permanently magnetic, or of electrically nonconducting matter. The ends
of the bobbin of high resistance are connected with the extremities of the portion
of an electric circuit whose supply of energy we wish to measure, the main current
or any fractional portion of the main current being allowed to pass through the
coils of smaller resistance.
It is well known that the Torque or average force acting between the movable
& fixed parts is proportional to the product of the currents flowing in them, and
this is evidently proportional to the horse-power which is being expended
in the main circuit, hence the horse-power so expended multiplied by the velocity
with which the movable part is made to rotate, is proportional to the mechanical
power given out by the Motor. If now the only work done by the Motor is
done in overcoming fluid friction, or in causing magnets to revolve in front of
metallic plates, such as copper, as in Arago's disc experiments, the forces resisting
motion are proportional to the velocity, and it is obvious that the number of
revolutions made by the Motor in any time is proportional to the electrical
energy given to the circuit in that time. The only work therefore done by the
Motor is the moving of vanes in the liquid or in the relative motion of magnets
and conductors, with the exception of the small amount of work necessarily done
in overcoming the friction at the bearings of the machine.
The number of revolutions made by the motor in any time is determined in much
the same way as that employed in gas or water meters, and the electric energy given
to a house or a machine or a lamp, or any other contrivance or number of
contrivances during any period of time is represented by the difference of the
readings of the Instrument at the begining and end of the time in question, just as
in a gas or water meter the quantity of gas, or the quantity of water is measured.
Steel or cast iron must not be used either in the armature or fixed parts of the
machine, and indeed it is probably preferable not to use in the moving parts any
metallic core, as the induction currents give rise to a prejudicial resistance. In
some of our Instruments the armature coils have nonconducting cores.
In saying
that our Instrument is shaped like a Dynamo Machine we do not confine ourselves
to this shape.
The distinguishing characteristic of the Machine is that when it moves under the
action of electricity the average forces causing motion, are proportional to the
product of the current flowing in the fixed and movable parts, one of these currents
being proportional to the whole, or a fractional part of the main current and the
arrangment made for resisting motion may be any one in which the resistance is
proportional to the speed, so that the mechanical power wasted is proportional to
the square of the speed. Some constant frictional resistance will necessarily be
present, but it is reduced as much as possible and the correction for it is made
by adding to the reading a certain number multiplied by the time which has
elapsed.
Another method employed by us to register the energy given electrically to any
circuit is of the nature of an addition to a pendulum or balance or other regulator
of a clock or watch. On such vibrating regulators we place a coil of wire, and in
the neighbourhood, perfectly fixed in position we have another coil of wire. One
of these coils has great resistance and connects the two extremities of the part of
the circuit about which we wish to have a record, so that the current flowing in it
is proportional to the difference of potential,

page_text: Through the other coil passes the whole or any fractional part of the main
current. These coils are so placed that the attractions or repulsions between them
would, in the absence of gravity or of the forces of springs, cause a very slow
vibration of the regulator. The effect of their being added to the ordinary forces
is to slightly quicken or shorten the time of vibration of the regulator. If this
shortening or quickening is a small fraction of the whole time of vibration, we
have proved that the loss or gain of the time keeper from what the recorded time
would be if there were no electric current is proportional to the total energy given
to the circuit in any time. If, however, the shortening or quickening of time of
vibration is large compared with the whole time of vibration the loss or gain of
the timekeeper is no longer proportional to the total energy.
We are aware that Electro-Motors as well as electric clocks, have been employed
to measure the quantity of electricity that has passed through a circuit, but a
knowledge of the quantity of electricity that has passed gives no indication of the
work the electricity has done and our Instruments are not designed to record the
quantity of electricity that has passed, but instead, the electric energy previously
given to a circuit, that is they record the time integral of current into electro-
motive force.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Edward Ayrton and John Perry in the Great Seal
Patent Office on the 5th December 1882.
WILLIAM EDWARD AYRTON, Professor of Technical Physics, Fellow of the Royal
Society and JOHN PERRY Professor of Mechanical Engineering and Applied
Mathematics in the City and Guilds of London Technical College, Finsbury in
the County of Middlesex CONTRIVANCES FOR REGISTERING THE AMOUNT OF
WORK GIVEN ELECTRICALLY TO ANY PART OF AN ELECTRIC CIRCUIT IN A GIVEN
TIME
To measure Electrical energy given to a house or to any Motor or Lamp or
other contrivance during a given time it is at present necessary to us such an
instrument as our Voltmeter to measure the difference of potential existing at any
instant between the two extremities of the portion of a circuit in which the
expenditure of energy occurs and at the same instant to measure with such an
instrument as our Am-meter the current flowing. The product of these measure-
ments multiplied by a certain constant number tells the horse power which is at
that instant being given electrically to the circuit or the horse power being
expended at any moment may be measured by an Instrument like our Electric
Power Meter. If these operations are repeated at equal intervals of time it is
possible to calculate approximately the electric energy given to the circuit in any
time during which observations are constantly being made.
Our present invention is an Instrument which continually performs this operation
and shows by pointers on dials the total amount of energy which has passed
electrically into a circuit since any previous date. It consists of a small machine
shaped like a dynamo-electric machine. The moveable field magnet of this
machine is wound with moderately thick wire. The fixed armatures are wound
with a wire whose resistance may be more than Two Hundred Ohins, or again the
moving part may have a considerable resistance and the fixed may have the
smaller resistance. The cores in both cases may be of very soft iron, or other
magnetic matter, or they may be of non-magnetic matter so that they cannot
become permanently magnetic or of electrically non-conducting matter. The ends
of the bobbin of high resistance are connected with the extremities of the portion
of an electric circuit whose supply of energy we wish to measure; the main current
or any fractional portion of the main current being allowed to pass through the
coils of smaller resistance.
It is well known that the Torque or average force acting between the moveable
and fixed parts is proportional to the product of the currents flowing in them and
this is evidently proportional to the horse power which is being expended in the
main circuit, hence the horse power so expended multiplied by the velocity with
which the moveable part is made to rotate is proportional to the mechanical power
given out by the motor. If now the only work done by the motor is done in
overcoming fluid friction or in causing magnets to revolve in front of metallic
plates such as copper or as in Arago's disc experiments in all these cases the forces
resisting motion are proportional to the velocity, and it is obvious that the number
of revolutions made by the Motor in any time is proportional to the electrical
energy given to the circuit in that time. The only work therefore done by the
motor is the moving of vanes in the liquid or in the relative motion of magnets
and conductors with the exception of the small amount of work necessarily done
in overcoming the friction at the bearings of the machine, and in moving the
recording apparatus. The number of revolutions inade by the motor in any time is 5

page_text: determined in much the same way as that employed in gas or water meters and
the electric energy given to a house, or machine, or a lamp, or any other contrivance,
or number of contrivances during any period of time is represented by the
difference of the readings of the instrument at the beginning and end of the time
in question, just as in a gas or water meter the quantity of gas or the quantity of
water is measured. Steel or cast iron must not be used either in the armature or
fixed parts of this machine and indeed it is probably preferable not to use in the
moving part any metallic core, as the induction currents give rise to prejudicial
resistance. In some of our instruments the armature coils have non-conducting
cores.
In saying that our instrument is shaped like an electromotor we do not confine
ourselves to the shapes of existing electromotors the distinguishing characteristic
of the machine is that when it moves under the action of electricity the average
forces causing motion are proportional to the product of the currents flowing in the
fixed and moveable parts, one of these currents being proportional to the whole or
a fractional part of the electromotive force in the main circuit, and the other being
the whole or a fractional part of the main current. The arrangement made for
resisting motion may be any one in which the resistance is proportional to the
speed so that the mechanical power wasted is proportional to the square of the
speed. Some constant frictional resistance will necessarily be present, but it is
reduced as much as possible and the correction for it is made by adding to the
reading a certain number multiplied by the time which has elapsed. Another
method employed by us to register the energy given electrically to any circuit is of
the nature of an addition to a pendulum or balance, or other regulator of a clock or
watch. On such vibrating regulator we place a coil of wire, and in the neighbour-
hood perfectly fixed in position we have another coil of wire. One of these coils
has great resistance and connects the two extremities of the part of the circuit
about which we wish to have a record so that the current flowing in it is
proportional to the difference of potential. Through the other coil passes the
whole or any fractional part of the main current these coils are so placed that the
attractious or repulsions between them would in the absence of gravity or of the
forces of springs cause a very slow vibration of the regulator if displaced from the
mean position. The effect of their being added to the ordinary forces is to slightly
quicken or shorten the time of vibration of the regulator. If this shortening or
quickening is a small fraction of the whole time of vibration we have proved that
the loss or gain of the time keeper from what the recorded time would be if there
were no electric currents is proportional to the total energy given to the circuit in
any time. If however the shortening or quickening of time of vibration is large
compared with the whole time of vibration the loss or gain of the time keeper is no
longer proportional to the total energy. We are aware that electromotors as well
as clocks have been employed to measure the quantity of electricity that has passed
in a circuit, but a knowledge of the quantity of electricity that has passed give no
indication of the work the electricity has done and our instruments are not
designed to record the quantity of electricity that has passed but instead the
electric energy previously given to a circuit, that is they record the time integral
of current into electromotive force.
Having now described the nature of our invention and the manner in which it
may be practically carried out we beg to say that what we consider to be novel
and original, and therefore claim as the invention secured to us by the herein before
in part recited letters patent is: (1) In measuring the total amount of energy given
to an electrical circuit the use of an electromotor whose fixed and moveable parts
have soft iron or else non magnetic cores wound respectively with a coil or coils of
small resistance through which the main current of the circuit passes and a coil or
coils of bigh resistance through which passes a current proportional to the
difference of potentials at the ends of the circuit in question, the motion of the
motor being resisted by vanes immersed in a fluid or by any other resistance which
is proportional to the velocity substantially as described. (2) In measuring the

page_text: energy given to an electrical circuit the placing a coil or coils of wire of high
resistance on a pendulum bob or on the balance of a watch or in place of the
pendulum bob or balance through which a current is allowed to pass which is
proportional to the difference of potentials at the ends of the circuit in question;
this coil vibrating near a fixed coil or coils of small resistance through which the
main current of the circuit passes or placing the small resistance coil on, or in place
of, the bob of the pendulum of a clock or the balance of a watch and allowing it to
vibrate near the fixed high resistance coil in both cases the attractive or repulsive
electrical forces between the coils being small in comparison with the weight of the
pendulum bob or the force of the balance spring so that the gain or loss of time
due to electrical action is only a small fraction of the whole interval of time.
In witness whereof we the said William Edward Ayrton and John Perry
have hereunto set our hands and seals this fifth day of December in the
year of our Lord 1882
W. E. AYRTON. (L.S.)
JOHN PERRY. (L.S.)