US954619A - Instrument for detecting electric oscillations. - Google Patents

Description

J. A. FLEMING.

INSTRUMENT FOR DETECTING ELECTRIC OSGILLATIONS.

APPLICATION FILED JAN.2, 1909.

954,61 9, Patented Apr. 12, 1910.

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INSTRUMENT FOR DETECTING ELECTRIC OSQ ILLATIOIIS.

application filed January 5,1909. s riainonu'oaga To' all whom it may concern:

Be it known that I, J 01am AMBRosE FLEM- of lege, Gower Street, in the county of London, England, have invented new and useful Imrovements in Instruments for Detecting lectric Oscillations, of which the following is a specification.

My invention has reference to that type of electrical oscillationdetector described by me in the United States patent specification No. 808684 dated 7th November 1905.

In this specification I described an oscillation detector subsequently called an oscillation 'valve or glow lampdetector, which consists of an electric glow lam of the ordinary type, but having within t e glassbulb a metal plate or cylinder carried on an insulated terminal sealed through the glass. When-the filament is rendered incandescent by an electric current, it emits negative ions or corpuscles or electrons and these ionize the residual gas in the bulb, and give to the space a unilateral conductivity by which negative electricity can pass from the hot filament to the cold insulated plate or cylinder within the bulb, but not in the opposite direction. I employed this device as an electric wave detector in radiotelegraphy by connecting the insulated plate or cylinder to one terminal of an oscillation transformer inserted in the receiving circuit of the radiotelegraphic apparatus, and the other terminal of this oscillation transformer was connected through a galvanometer or telephone to the negative terminal of the filament. 7

I have discovered after many ex eriments that tungsten in various forms an particularly a form in which it is employed as the filament in a glow lamp is highly e cient for this purpose since the amount of negative.

ms doctor of science a subject of the King ireat Britain, resi ing at University Col- I specification 01!LettersIkatent. Patented Apr,-

they can be worked in ractice. I have also discovered that a cylinder of carbon acts better-as the cold conductor in the bulb than the metallic cylinders heretofore employed.

" perior tocarbon at-any temperature at which I construct such a metallic or semi-metallic filament glow lamp with a tubular glass bulb and a cyhnder of carbon sealed into the bulb,

and connected to a platinum"wire sealed throu h the glass. "Furthermore, I employ .this g ow lamp as an oscillation detector as follows :The' filament is rendered incandescent by an insulated battery having in series with it a rheostat or variable resistsurrounding but not touching th m K ance for controlling the current. Across the terminals of this battery -I place another high resistance having a sliding contact in it, so as to make contact with any desired point on this resistance.

In using this detector in wireless teleg- 7 raphy the receiving circuit must comprise a closed circuit having inductance and containing a condenser. If the telegraphy is conducted by electric waves it is necessary also to connect an antenna either directly ,or indirectly with this condenser circuit. I

then connect the insulated cylinder included within the bulb of the lamp with one plate of the condenser in the oscillation circuit, and I connect the othenplate of this 5 condenser with the sliding contact on the re sistance across the glow lam battery terminals. In this circuit I also include a telephone or current detecting instrument. A

the filament rendering it incandescent, and also in virtue of the-emissionof negative electricity from the filament a current flows from it through the vacuous space to the metal cylinder and through the telephone or I other current detector. The conductivity of this vacuous space or ionized rarefied gas is a function of the electromotive force acting to drive the current through it. I find that if the position of the sliding contact on the resistance across the terminals of the battery is so adjusted that corresponding thereto the conductivity curve of the ionized gas has a very sudden change in curvature,

the superppsition of an oscillatory potential difiere'nce between the filament and cylinder upon the steady potential diflerence causes I very sudden changes in the current strength current then flows from the battery through 90 I electric waves or magneto electric induction tion I place across the termina intelligence to a distance.

In the drawing accompanying and forming a part of this specification, I have illustrated one embodiment of my invention. Referring to this drawing it will be seen that in carrying my invention into efiect I employ a tubular form of glass bulbca which may be an inch or more in diameter and five or six inches in length. In this I insert a cylinder b of carbon which is sprung into the glass tube so as to fit the walls tightly. This cylinder has a platinum wire a twisted or welded to it which is sealed through the glass, so as to make an external electrical connection. The bulb a should have a good vacuum such as is usually employed with lamps having metallic filaments.

The metallic filament d is formed of tung-.

sten in the form used as a filament in ordi-' nary glow lamps and is connected to conductors 6 carried on a lass tubular stem 7 sealed into the bulb. T e filament (1 should be of such a length that it is entirely covered by the metal cylinder 6. It is convenient to have the filament of such length and thickness that the voltage required to bring it to incandescence at which its durationmay not be less than several hundred hours, is of the order of 18 volts or so.

In applying this glow lamp as a detector in radiotelegraphyl arrange it as follows A battery 9 o seconda cells is provided which may conveniently e a dozen or more cells, and wires h are brought from the terminals of thisbattery to the terminals e of the filament of the lamp, a variable resistance j'k being inserted in the circuit. It is convenient to divide this resistance into two,

one namely of from say 0 to. 120 ohms be-- ing for coarse adjustment and the other is of from sa O'to 5 ohms being for fine adjustment. means of these resistances the current of the lamp ma be adjusted to have any required value. X voltmeter I should also be placed across the terminalsof the filament to regulate the volta e. In addiof the battery g a high resistance m of the potenti: ometer type, that is to say, a resistance which may be two or three hundred ohms or more, the terminals of which are connected 'serted in a circuit possessing in to the terminals hot the batter A double high resistance telephone 12. (t ef resistance of each telephone being at least five or six hundred ohms) has one terminal connected to a slider 0 which can make contact with any required point on the resistance m and the other terminal connected to one late of a condenser 32. The other plate of t e condenser p is connected with the metal cylinder of the lamp. The condenser is indiictance, which is directly or inductively connected with a receiving antenna. As shown thecircuit connecting the two plates of the condenser p contains an adjustable -1nductance g and the secondary of the jigger r the primary of which is in the aerial .9. When electric waves fall upon the receiving antenna they excite oscillations in the condenser circuit and oscillations are thus imposed upon the telephone circuit connectin the metal cylinder or plate in the lamp with the sliding contact and high resistanceconnected across the terminals of the battery or other source of continuous electric current.

In operating the arrangement, the first step is to bring the filament to a high incandescence at which it would be working a proximately at one watt per candle and at w liich it will have such a temperature, approximately 2800 0., that it will diffuse into the vacuous space negative ions discharged from the incandescent filament. The filament having been rendered incandescent to this temperature,fthe observer applies the telephone to his ear and if electric wave trains are falling u on the receiving antenna 8, it'will be foun that on moving the slider 0 along the potentiometer resistance m from one end to the other, there is a certain point at which sounds will be heard in the telephone better than at any other point. The exact osition of the slider 0 must be determine by trial for it varies with every valve owing to slight dilferences in the vacuum and temperature of the filament. The detector above described is suitable as the receiver in radiotelephony, as well as for signals on the Morse or other a1 habetic code.

- atIclaim-is:-

1. A rectifienor valve for electric oscillations, having one electrode composed of tungsten.

2. A rectifier or valve for electric oscillations, having one electrode composed of tgungsten and one element composed of car- 3. A rectifier or valve for electric oscillations, comprising a metallic filament constituting one electrode, means for heating said filament, and a plate ofcarbon constituting another electrode thereof.

4. A rectifier 0r valve for electric oscilla tions, comprising a. metallic filament constiloo tuting one electrode, means for heating said filament, and a curved plate of carbon circumferentially situated. in relation to the longitudinal axis of said filament.

5. An oscillation valve in which the hot conductor is a filament of tungsten.

6. An oscillation valve com rising a heated electrode in combination with a cold electrode consisting of a mass of carbon.

7. An oscillation valve comprising a heated electrode in combination: with a cold electrode consisting of a cylinder of carbon.

8. An oscillation valve in which the hot conductor is a filament oftungsten and the cold conductor is a cylinder of carbon.

9. The combination of an oscillation valve, a source of electricity heating the filament of the valve, a resistance across the terminals of the source, a circuit connected atone end to the cold conductor of the valve and 10. In combination with an oscillation valve, a source of electric current for energizing the filament thereof, an oscillatory 1 circuit having one terminal connected wit one element of said oscillation valve, the other terminal of said oscillatory circuit be- .ing adjustably connected With a resistance hich is connected with op oslte terminals of another element of sai valve, and a translating device operatively connected with said circuits for indicating the presence of electric oscillations. 4

JOHN AMBROSE FLEMING. Witnesses:

Gno. J. B. FRANKLIN, I T. J. OSMAN.

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