Improvements in Apparatus for Measuring and Regulating Electric Currents.
Year: 1889

page_text: Date of Application, 21st Nov., 1889
Complete Specification Left, 21st Aug., 1890-Accepted, 11th Oct., 1890
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Measuring and Regulating
Electric Currents.
JOHN PERRY of 10 Penywern Road S.W. Fellow of the Royal Society, CHARLES
EDWARD HOLLAND of 4 Redington Road Hampstead London N.W., and HENRY
BLECKLY BOURNE of 41 Priory Road, Bedford Park, London W. Electrical
Engineers do hereby declare the nature of this invention to be as follows:
When an electric current is passed through a wire or other conductor, the wire
or other conductor is heated and a thermometer placed near the wire in a fixed
position relatively to the wire will by its indications of temperature really serve
as an indicator or measurer of current. For more exact work both conductor &
thermometer ought to be placed inside a metallic case and the thermometer ought
to be one which only indicates difference of temperature from that of the case, else
two readings must be taken, one of the thermometer itself and another which
gives the temperature of the case. We find that, when a current is passed through
the conductor, some metallic thermometers reach a steady final state sufficiently
quickly to be more valuable than others to electricians; particularly a stretched
wire of metal which indicates its temperature by altering in length, this altera-
tion in length being magnified in any of the well known ways of magnification of
small motions known to instrument makers.
Again, one of us, with Professor Ayrton has patented the use of a stretched
twisted strip of metal as a thermometer, since a pointer attached to the strip
rotates when change of temperature occurs. Again, a double strip consisting of
two strips of different metals attached side by side to one another, coiled into a
spiral is known to act well as a thermometer on account of the different rates of
expansion of the two metals.
Now we do not pass the electric current to be measured through these metallic
thermometers we pass the electric current through a neighbouring conductor
and we prefer to have the conductor, whether metallic or of carbon as a spiral of
wire or of strip partly surrounding the thermometer, or as a tube partly surround-
ing the thermometer. Almost any thermometer may be used, however, such as an
air thermometer whose case is metallic. Again Dr. Siemens used the change of
resistance which occurs in a wire to indicate change of temperature and such a
wire would serve as the thermometer of our invention. By contrivances which are
well known to clectricians such a change of resistance may be employed for
various purposes of regulation in electrical distribution. Instead of using tho
thermometer in the measurement of currents we may let the thermometer, by its
behaviour, regulate contrivances; thus if the current were too great, the thermo-
meter might introduce resistance into a circuit or break a circuit or perform any
other governing or regulating function.
We never use the well known mercury thermometer as the thermometer of our
invention, when merely wanting to measure electric currents; but we do use it as
an indicator & regulator, platinum wires passing through the glass making con-
tacts with the mercury when the current and therefore the temperature becomes
great enough:
Again, an air or other thermometer which is part of a pendulum of a clock &
which is such that when it is heated there is a raising or a lowering of the centre
of gravity of the pendulum, acts as a thermometer by giving a loss or gain of

page_text: rate of going to the clock. Such thermometers as these may in certain cases be
used in the indication or measurement of current.
Dated this 20th day of November 1889.
JOHN PERRY,
CHARLES EDWARD HOLLAND,
HENRY BLECKLY BOURNE.
Improvements in Apparatus for Measuring and Regulating
Electric Currents.
We, JoHN PERRY of 10 Penywern Road, London S.W. Fellow of the Royal
Society, CHARLES EDWARD HOLLAND of 4 Redington Road, Hampstead, Electrical
Engineer and HENRY BLECKLY BOURNE of 41 Priory Road, Bedford Park,
London W. Electrical Engineer, 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:-
When an electric current is passed through a wire or other conductor, the wire
or other conductor is heated and a thermometer placed near the wire in a fixed
position relatively to the wire will by its indications of temperature really serve
as an indicator or measurer of current. For ntore exact work both conductor &
thermometer ought to be placed inside a metallic case & the thermometer ought
to be one which only indicates difference of temperature from that of the case, elso
two readings must be taken, one of the thermometer itself. & another which gives
the temperature of the case.
We find that when a current is passed through the conductor, some metallic
thermometers reach a steady final state sufficiently quickly to be more valuable
than others to electricians; particularly a stretched wire of metal which indicates
its temperature-by altering in length, this alteration in length being magnified
in any of the well known ways of magnification of small motions known to instru-
ment makers.
Again, one of us, with Professor Ayrton, has patented the use of a stretched
twisted strip of metal as a thermometer, since à pointer attached to the strip
rotates when change of temperature occurs. Again, a double strip consisting of
two strips of different metals attached side by side to one another, coiled into a
spiral, is known to act well as a thermometer on account of the different rates of
expansion of the two metals.
Now we do not pass the electric current to be measured through these metallic
thermometers we pass the electric current through a neighbouring conductor
and we prefer to have the conductor, whether metallic or of carbon as a spiral of
wire or of strip partly surrounding the thermometer or as a tube partly sur-
rounding the thermometer.
Almost any thermometer may be used, however, such as an air thermometer
whose case is metallic. Again Dr. Siemens used the change of resistance which
occurs in a wire to indicate change of temperature & such a wire would serve as
the thermometer of our invention. By contrivances, which are well known to
electricians, such a change of resistance may be employed for various purposes
of regulation in electrical distribution.
Instead of using the thermometer in the measurement of currents we may let it
by its behaviour, regulate contrivances; thus if the current were too great, the
thermometer might introduce resistance into a circuit or break a circuit, or per-
form any other governing function.
We do not care to use the well-known mercury thermometer as the thermometer
of our invention when merely wanting to measure electric currents, because it is
too sluggish; but we do use it as an indicator & regulator, platinum wires

page_text: passing through the glass making contact with the mercury when the current
and therefore the temperature reach limiting values.
Again, an air or other thermometer which is part of the pendulum of a clock
and which is such that when it is heated there is a rising or lowering of the centre
of gravity of the pendulum, acts as a thermometer by giving a loss or gain of rate
of going to the clock. Such thermometers as these may in certain cases be used
in the indication or measurement of current.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:
1
1. The use of a thermometer in the neighbourhood of an electric conductor for
indicating or measuring current or for regulating purposes as described.
2. The use of a thermometer in the neighbourhood of an electrical conductor
which makes electric contacts or introduces resistance or breaks circuits for
indicating & regulating purposes.
3. The use of a thermometer in the neighbourhood of an electric conductor
which alters the position of the centre of gravity of part of the regulator of a
clock when the temperature alters & so produces a loss or gain of rate of going.
4. The use as the thermometer of our combination of a stretched wire which
alters in length when its temperature is altered.
5. The use as the thermometer of our combination of a stretched twisted strip
of material which twists or untwists when its temperature is altered.
Dated this 15th day of August 1890.
JOHN PERRY,
CHARLES EDWARD HOLLAND,
HENRY BLECKLY BOURNE.