Improvements in Electric Thermometers and Thermographs.
Year: 1890

page_text: Date of Application, 15th July, 1890
Complete Specification Left, 14th Apr., 1891-Accepted, 16th May, 1891
PROVISIONAL SPECIFICATION.
Improvements in Electric Thermometers and Thermographs.
We, JAMES WYARD GOOCH of High Street, Windsor, Berks, Surgeon,
CHARLES ASHMORE BAKER of 58 Bread Street, in the County of London,
Electrical Engineer and WILLIAM WHITE of 58 Bread Street, in the County
of London, Electrical Engineer, do hereby declare the nature of this invention to
be as follows:-
Our invention relates to thermometers and thermographs in which the difference of
electrical resistance produced in different conductors by variations of temperature
is utilised for indicating these variations of temperature. In an electric thermometer
according to our invention a current from a battery or other source of electricity is
divided into two parts which pass through wire coils of different metals such, for
instance as iron and German silver, the electrical resistance of the one being
increased or diminished by change of temperature to a greater extent than that of
the other. Conductors from these coils will lead to opposite ends of a galvanometer
coil and also to opposite ends of a stretched wire along which a contact can be slid,
this contact having a return wire extending from it to the battery.
In the conducting lines resistances are adjusted so that at a certain normal
temperature the sliding contact being at the middle of the stretched wire the
galvanometer shall stand at zero. When the temperature changes, the resistance of
the one line of conductor becomes greater or less than that of the other, causing the
galvanometer needle to be deflected to the one side or the other. By sliding
the contact along the wire until the resistance in the two lines becomes equalised,
the galvanometer can be brought back to zero, and the distance which the contact
has thus been moved from the middle position will give an indication of the
temperature. In applying this principle to a thermograph by which the variations
of temperature are recorded, we provide suitable clockwork driving a paper drum
or other recipient surface and a spindle having on it two bevil wheels either of which
can be slid into gear with a bevil wheel on a screw spindle. The galvanometer
needle, when it is deflected to the one side or the other in consequence of a change
of temperature makes a contact whereby the one or the other of the two electro-
magnets is brought into circuit. An armature between them is thus attracted to
the one side or the other and it moves the bevil wheels on the spindle above
mentioned sliding the one or the other into gear with the bevil wheel on the screw
spindle which is thus caused to revolve in the one direction or the other. This
revolution of the screw spindle moves the sliding contact along the stretched wire
until the resistances of the two lines of conductor are equalised and the galvano-
meter needle returns to zero, opening the circuit of the electro magnet so that the
armature is brought back to middle position by a spring disengaging the bevil gear
and stopping the screw spindle. The sliding contact moves with it a tracer
which marks on the paper drum a line corresponding to the movement of the contact
and therefore indicative of the temperature.
Instead of employing a sliding contact to equalise the resistances of the two lines
of conductor as above described the galvanometer needle may be free to be
deflected over a considerable range, its end moving over the revolving paper
drum, and having a marker which at regular intervals of time is depressed so as
to make dots or marks on the paper indicative of the temperatures at those
times.
Dated this 15th day of July 1800
ABEL & IMRAY,
Agents for the Applicants.

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Thermometers and Thermographs.
We, JAMES WYARD GOOCH of High Street, Windsor, Berks, Surgeon,
CHARLES ASHMORE BAKER of 58, Bread Street, in the County of London,
Electrical Engineer, and WILLIAM WHITE of 58, Bread Street, in the County
of London, 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 :-
Our invention relates to thermometers and thermographs in which the difference
of electrical resistance produced in different conductors by variations of temperature
is utilised for indicating these variations of temperature. In an electric thermometer
according to our invention a current from a battery or other source of electricity is
divided into two parts, which pass through wire coils of different metals such, for
instance as iron and German silver, the electrical resistance of the one being
increased or diminished by change of temperature to a greater extent than that of
the other. Conductors from these coils will lead to opposite ends of a galvano-
meter coil and also to opposite ends of a stretched wire along which a contact
can be slid, this contact having a return wire extending from it to the battery.
In the conducting lines resistances are adjusted so that at a certain normal
temperature the sliding contact being at the middle of the stretched wire the
galvanometer shall stand at zero. When the temperature changes, the resistance
of the one line of conductor becomes greater, or less than that of the other, causing
the galvanometer needle to be deflected to the one side or the other. By sliding
the contact along the wire until the resistance in the two lines becomes equalised, the
galvanometer can be brought back to zero, and the distance which the contact has
thus been moved from the middle position will give an indication of the temperature.
In applying this principle to a thermograph by which the variations of temperature
are recorded, we provide suitable clockwork driving a paper drum or other recipient
surface and a spindle having on it two bevil wheels either of which can be slid into
gear with a bevil wheel on a screw spindle. The galvanometer needle, when it is
deflected to the one side or the other in consequence of a change of temperature
makes a contact whereby the one or the other of the two electro-magnets is brought
into circuit. An armature between them is thus attracted to the one side or the
other and it moves the bevil wheels on the spindle above mentioned sliding the one
or the other into gear with the bevil wheel on the screw spindle which is thus caused
to revolve in the one direction or the other. This revolution of the screw spindle
moves the sliding contact along the stretched wire until the resistances of the two
lines of conductor are equalised and the galvanometer needle returns to zero,
opening the circuit of the clectro magnet. The sliding contact moves with it a
tracer which marks on the paper drum a line corresponding to the movement of the
contact and therefore indicative of the temperature.
Instead of employing a sliding contact to equalise the resistances of the two lines
of conductor as above described the galvanometer needle may be free to be deflected
over a considerable range, its end moving over the revolving paper drum, and
having a marker which at regular intervals of time is depressed so as to make dots
or marks on the paper indicative of the temperatures at these times.
Figure 1 of the accompanying drawings is a diagram illustrating the electrical
connections for a recording thermograph according to our invention, a plan of which
is shewn by Figure 2.
Referring first to Figure 1, B is a battery from one terminal of which a con-
ductor 6 leads the current which divides itself through two coils C¹ C³ of different
metals, the two portions of the current passing thence by conductors c c to
points where they are connected with adjusted resistances R' R' at the ends
of a stretched wire w and also by conductors gg2 to the coils of a galvanometer G

page_text: A contact slides connected to the other terminal of the battery B can be slid
along the wire W until the galvanometer G is brought to zero. Another battery L
is connected through either of two contacts n¹ n' made by the galvanometer
needle N. with either of two electro magnets E' E', which, as will presently be
explained, determine the movement of the sliding contact S along the wire W. At
the ends of the stroke of S there are spring contacts in the circuits of the
magnets E' E' which circuits are opened when the sliding contact S has made its
full stroke in each direction.
In Fig. 2, A indicates clockwork which drives the recording drum D on which a
tracer T marks the movement of the sliding contact S along the wire W. The
contact S is moved by the rotation of a screw F in the one direction or the other
as determined by the reversing bevil gear fon a spindle worked by clockwork H,
this spindle being moved longitudinally by the armature e when it is attracted by
the one or the other of the two electro-magnets E' E². The clockwork H at
certain recurring intervals, such as once every five seconds, moves a lever h which
pushes down an arm on a rocking spindle K, another arm of which is immediately
over an arm N extending from the needle of the galvanometer G. According as
the end of the arm N when it is pushed down is over the one or the other of two
contacts n' n³, the current from the local battery L (Fig. 1) is made to excite the
one or the other of the two magnets E' or E', so that the armature e is attracted to
the one or the other shifting the bevil pinions of and so determining the direction
in which the screw F rotates, and consequently the direction in which the contact S
moves along the wire W.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is :-
1. The herein described method of indicating variations of temperature by
connecting the ends of a stretched wire to a source of electricity through coils of
two metals having their electrical resistance differently affected by temperature,
and sliding a contact along that wire until a galvanometer which is also connected
to its ends indicates equality of resistance in both circuits.
2. The construction of thermograph wherein the sliding of the contact along the
wire above referred to is effected by clockwork and has its direction determined by
the one or the other of two electro-magnets brought into circuit by the galvano-
meter, the movement of the contact being traced on a revolving drum, substantially
as described.
Deted this 14th day of April 1891
ABEL & IMRAY,
Agents for the Applicants.