Year: 1886

page_text: Date of Application, 31st May, 1886.
Complete Left, 28th Mar., 1887.
Complete Accepted, 24th May, 1887.
I, MORITZ IMMISCH, of 119 Torriano Avenue, Camden Town, London, in the County
of Middlesex, Electrician, do hereby declare the nature of this invention to be as
follows:-
:―
This invention relates to an apparatus for measuring heat. It is well known that
the electrical conductivity of different substances is affected by changes of temperature
in such conductors. I make use of this well known effect and employ it in conjunction
with the Wheatstone bridge arrangement, by subjecting one or more arms of the
bridge (which I will call the active arm or arms) to the source of heat to be measured,
and arrange the remaining bridge arms (which I will call the passive arms) in such a
way as to cause the changes of resistance in the latter, which are necessary to establish
a balance, to be indicative of the degree of heat acting on the former. The choice of
conducting substances depends upon the use for which the apparatus is intended.
In the case of very high degrees of heat to be measured, such as is found in furnaces
for metallurgical operations, I prefer to make the active arms one of carbon and the
other of platinum. It is well known that the resistance of carbon decreases while
that of platinum increases with an increase of temperature, and any heat applied will
disturb the existing relation of resistances. The use of the Wheatstone bridge
principle enables me to be independent of the resistance per se and of the current
passing at any particular time. The calibration is performed empirically by moving a
sliding contact in one of the passive arms along till a balance is obtained; the extent
of such movement is the measure of heat acting on the active arm or arins, and is
indicated by a pointer on a suitably divided dial.
An apparatus such as this can also be used for clinical purposes.
The great advantage is that the indication can be observed away from the source of
heat, while the active arm or arms are subjected to it.
ALLISON BROS.,
Agents for the Applicant.

page_text: I, MORITZ IMMISCH, of 119 Torriano Avenue, Camden Town, London, in the County
of Middlesex, Electrician, 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 :-
This invention relates to an apparatus for measuring heat. It is well known that
the electrical conductivity of different substances is affected by changes of temperature
in such conductors. I am aware that this effect has been already utilized for
measuring heat, but my invention consists in making use of such well known effect
in conjunction with a Wheatstone bridge arrangement in which the arms are made of
.carbon and of metal, whereby the effect produced by the changes of temperature to
which the apparatus is subjected is increased or multiplied, and the resistance which it
is necessary to insert or withdraw in order to reestablish the balance of the bridge and
bring the galvanometer back to the zero position, will be indicative of the degree of
heat to be measured.
The choice of conducting substances depends upon the use for which the apparatus
is intended. In the case of very high degrees of heat to be measured, such as is
found in furnaces for metallurgical operations, I prefer to make the arms of the bridge
of carbon and of platinum, but where the heat to be measured is not so intense (such
as when applying the invention to apparatus for clinical purposes), I prefer to use
silver or copper in place of platinum.
It is well known that the resistance of carbon decreases while that of silver, copper
and platinum increases with an increase of temperature, and any heat applied will
disturb the existing relation of resistances. The use of the Wheatstone bridge
principle enables me to a large extent to be independent of the resistance per se and
of the current passing at any particular time. The calibration is performed empirically
by moving a sliding contact in one of the arms along till a balance is obtained; the
extent of such movement is the measure of heat acting on the apparatus, and is
indicated by a pointer on a suitably divided dial.
A suitable method of carrying my invention into effect is illustrated in the
accompanying drawing, which is a diagrammatic-view.
A, A', and C, C, represent the four arms of the bridge. A highly sensitive
galvanometer G is included in a circuit between the point of junction between the
arms A, A, and that of the arms C, C, and a battery B is included in a circuit
between the point of junction between arms A and C and that of arms A¹ and C.
The respective resistances of the arms are so arranged that at a given normal temperature
no current will pass through the galvanometer circuit, but above or below such
normal temperature a current will pass in one or other direction through such
galvanometer circuit.
A suitable variable resistance R is arranged in one of the arms, and is shown in the
drawing as applied to arm C, one-end-of-same being-connected by R' to C, while a

page_text: wire P¹ is also connected to such arm and to a pointer P capable of being moved
over resistance R, with which it is in contact.
Supposing arms A¹ and C to be subjected to the source of heat (one being of
carbon and the other of metal); and also supposing that I want to measure a
temperature of from 95 to 110 degrees, as would be requisite for clinical purposes,
I then arrange the resistances of the arms in such a way that at 95° no current shall
pass through the galvanometer G. Up to that point the current will pass through
the galvanometer G in one direction, and when the temperature of 95° is exceeded the
current will pass in the reverse direction. When the instrument has attained the
temperature of the source of heat, I move pointer P, along resistance R, until
a balance is reestablished. The position of the pointer P on the dial will then show
the temperature actually attained. As a matter of course the calibration of the
instrument is attained by submitting it to known temperatures and marking the dial
accordingly. It will be seen that pointer P serves both to reestablish the balance and
also to indicate the temperature on the dial.
It will also be readily understood that the sensitiveness of the instrument depends on
the ratio which resistance R bears to the whole resistance of the arm of which it forms
a. part.
By introducing into the arm C known resistances which can be either put in or
taken out at will, the same instrument may be used for indicating different ranges of
temperature.
Instruments of this description will be found very useful for clinical purposes, as the
whole may be made in a compact and portable form. As the parts to be exposed to
heat can be made slight and small without detriment to the efficiency of the instrument,
the indications are almost instantaneous, and readings may be taken without removing
the instrument from the patient, while for metallurgical and other purposes the
instrument will be found of great convenience in as much as readings may be taken
any distance away from the source of heat.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1. The apparatus for measuring heat consisting in a Wheatstone bridge arrange-
ment, in which carbon and metal forming different arms of the bridge are exposed to
the source of heat, while one of the arms is provided with means for introducing or
withdrawing resistance, so as to reestablish the balance which has been disturbed by
the heating effect changing the conductivity of the carbon and metal, all substantially
as specified.
2. In the heat measuring apparatus described in the preceding claim, the use of
pointer P serving both to vary the resistance of one of the arms of the Wheatstone
bridge arrangement, and to indicate the temperature on a graduated dial, substantially
as specified.
Data thin 28th day of Mar 1887
ALLISON BROS.,
Agents for the Applicant.