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Dec. 24, 1946.
‘
H. WOLFSON ET AL
‘2,413,021
RESISTANCE TYPE DETECTOR
Filed April 17, 1943
F/G. 2
J2“) Inventor I
‘ Attorney_
arisen
Patented Bee. 24, 1946
um'rso STATES PATENT-QFFHCE
2,413,021
7
RESISTANCE TYPE nn'rno'ron ’
Henry Wolfson and Stanley Garden Shepard,
London, England, assignors, by mesne assign
ments, to International Standard Electric Cor
poration, New York, N. Y., a corporation of
Delaware
‘
Application April 17, 1943, Serial No. 483,522
In Great Britain May 22, 1942
2 Claims.
>
(C1. 250—-25)
1
2
trolling the thermistor are arranged as a dipole
antenna for receiving the short waves and ap
plying them directly to the thermistor. The
This invention relates to resistance elements
for electric circuits, and particularly to those ele
ments known as thermistors which have a very
arrangement provides, for example, a simple and
high temperature coe?‘lcient of resistance,
accurate means of measuring the ?eld strength,
or with a suitable type of resistance element,
could be adapted as a detector.
According to the invention there is provided a
thermistor for measuring and/or detecting ultra
Thermistors have been in use for some years
and are characterised by a temperature coe?i-‘
cient of resistance which may be either positive
or negative and which is moreover many times
the corresponding coe?icient for a pure metal
such as copper. This property renders thermis 10 high frequency electromagnetic Waves, compris
ing a resistance element having a high tempera
tors particularly suitable for a variety of special
ture coe?icient of resistance assembled inside an
applications in electric circuits.
elongated glass bulb, and a pair of straight con
Various di?erent materials are available for
ductors passing outside the bulb at opposite ends
the resistance element of a thermistor, these
various materials having di?erent properties in 15 for leading the waves to the thermistor, the said
conductors being arranged in a straight line to
other respects; as one example, a resistance ma
form a dipole antenna, the lengths of the conduc
terial having a high negative temperature coeffi
tors being adjusted in accordance with the in
cient of resistance comprises a mixture of man
coming wavelength.
ganese oxide and nickel oxide, with or Without
The invention will be more clearly understood
the addition of certain other metallic oxides, the
from the following detailed descriptionof two
mixture being suitably heat treated.
Thermistors have been employed in two differ
embodiments with reference to the accompany
ent forms: (a) known as a directly heated
thermistor and comprising‘ a, resistance element
of the thermally sensitive resistance material
provided with suitable lead-out conductors or ter
minals, and (1)) known as an indirectly heated
ing drawing in which:
the current ?owing through it. An indirectly
heated thermistor is chie?y designed to be heated
by a controlling current which flows through the
heating coil and which will usually, but not nec
essarily, be different from the current which flows
through the resistance element; but this type of
ance element are arranged in the same straight
Fig. 1 shows a directly heated thermistor; and
Fig. 2 shows an indirectly heated thermistor,
both according to the invention.
Fig. 3 is an enlarged view of the thermistor ele
ment of Fig. 2.
thermistor comprising the element (a) provided
The ?rst embodiment of the invention is shown
in addition with a heating coil electrically insu
lated from the element. A directly heated 30 in Fig. 1. It shows a directly heated thermistor
bead l assembled in a cylindrical glass bulb 2.
thermistor is primarily intended to be controlled
This bead may comprise, for example, a resistance
by the current which flows through it and which
element consisting of thermally sensitive mate
varies the temperature and also the resistance ac
rial mounted on ?ne wires 1 and 8 similar to
cordingly. Such a thermistor will also be a?ected
that shown in Fig. 1 of the speci?cation of United
by the temperature of its surroundings and may
States Patent No. 2,282,944, dated May 12, 1942.
therefore be used for thermostatic control and
The lead-out conductors 3 and 4 for the resist
like purposes with or without direct heating by
thermistor may also be subjected to either or
both of the types of control applicable to a di
rectly heated thermistor.
More detailed information on the properties of
thermistors will be found in an article by G. L.
Pearson in the Bell Laboratories’ Record Dec.
1940, page 106.
The present invention relates to the construc_
tion of directly or indirectly heated thermistcrs
suitable for use at ultra high frequencies where
the wave length is of the order of a few centi
meters. The leads carrying the currents for con
~10
line and are sealed through corresponding presses
5 and 6 at opposite ends of the bulb 2. The ?ne
wires ‘I and 8 are welded to the lead-out con
ductors 3 and 4 in the manner indicated so as to
support the bead I. This operation may be con,
veniently done with the help of a suitable jig
for holding the parts together in the proper posi
tions.
The bulb 2 may conveniently be made from a
short length of glass tubing and may be ar
ranged to be slipped over the bead assembly while
on the jig, and may be scaled down onto the
lead-out conductors 3 and 4 forming the cor
responding presses 5 and 6.
An indirectly heated thermistor arranged as a
dipole is shown in Fig. 2 and Fig. 3. The bead
H is in this case provided with a heating coil l6
2,413,021
3
4
and may, for example, be generally similar to
diameter. The heating coil in Fig. 2 might have
that shown and described in connection with
Figs. 1 and 2 of U. S. patent speci?cation No.
2,280,257 or in the speci?cation of patent in Great
appropriate choice of the thermally sensitive
a resistance say from 50 to 200 ohms, and by
material, the resistance of the element in either
Britain No. 449,352 ?led July 4, 1942. The bulb UK embodiment may be given any value within a
l2 which encloses the bead II is similar to the
wide range. This element might, for example,
bulb 2 shown in Fig. 1 but has a short side tube
be composed of a mixture containing manganese
symmetrically placed and provided with a press
xide and nickel oxide, such as that described
l3. In this case, the lead-out conductors 9 and
in British patent speci?cation No. 540,844, with
10
ID for the heating coil are arranged in line to
,or without the addition of certain other metallic
form the dipole antenna and pass out of the bulb
oxides, in which case it would have a negative
through the presses 5 and 6. The lead-out con
temperature co-ef?cient of resistance. These
ductors 3 and 4 from the resistance element are
details have been given merely as examples and
arranged parallel to one another and pass out
not as limitations, and it will be evident that
of the bulb through the press l3 at right angles .
such details will be appropriately chosen With
to the leads 9 and Ill. The parts will prefer
the requirements of each particular case.
ably be assembled in a, suitable jig by Welding or
What is claimed is:
otherwise ?xing the wires l4 and I5 of heating
1. A device for detecting ultra high frequency
coil IE to the leads 9 and I0, and then slipping
electromagnetic waves, including a resistance ele
the bulb l2 over them and sealing as described 20 ment having a high temperature co-ef?cient of
in connection with Fig. l. The resistance ele
resistance, an elongated bulb havving said ele
ment IT, as shown in Fig. 3 may then be mounted
ment located therewithin, lead Wires connected
on the conductors 3 and 4 by welding or otherwise
to said element and extending through the walls
?xing the wires 1 and 8 thereto and may be
of said bulb at one side thereof, also including
coated with a suitable liquid cement. It may be
a heating coil mechanically integral with said
then slipped through the side tube of the bulb
12 into the heating coil l6 so as to be correctly
placed, and the press 13 ?nally sealed down onto
the conductors 3 and 4.
,
In the case of either embodiment of Fig. 1
or 2, the bulb may be ?lled with an inert gas
before sealing, or if preferred, a small side tube
may be provided for exhausting the bulb in the
usual Way.
.
It will be noted that the‘ dipole antenna is
formed by the resistance element leads in the
case of Fig. 1 and by the heating coil leads
in the case of Fig. 2. In either case, of course,
these leads will be cut to a suitable ‘length
having regard to the wave length which it is
desired to employ.
As an illustration, the resistance element might
be 0.02 inch diameter and the ?ne supporting
Wires might be platinum wires about 0.002 inch
element but electrically discrete therefrom, a
pair of straight conductors forming leads to said
heating coil and passing outside the bulbat op~
posite ends thereof for leading the waves to the
device, said conductors being arranged in a
straight line to form a dipole antenna, the
lengths of the conductors being adjusted in ac
cordance with the incoming wavelength, whereby
electrical coupling between said lead Wires and
said pair of conductors is minimized.
2. A device according to claim 1, in which
said lead wires include a pair of parallel con
ductors arranged symmetrically at right-angles
to said straight conductors, including a press
located on one side of said bulb for the passage
therethrough of said parallel conductors.
HENRY VVOLE‘SON.
STANLEY GARDEN SHEPARD.
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