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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.