USRE15469E - Thermionic voltmeter - Google Patents

Description

' R. A. HEISING. THERMIONIC VOLTMETER. APPLICATION FILED JULY 30. {519K Reissued Oct. 17, 1922; r 1 5 ,469.

hue/avianfig/mand A f/e/is/h M A/Vj/ Reissuea Oct. 17, 1922.

UNITED STATES-PATENT OFFICE.

RAYMOND A. EEISING, OF EAST ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- MEN'IS, 'IO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

.THERMIONIC VOLTMETER.

Original 110. 1,282,919, dated July 10, 1917, Serial No. 49,253, filed September 7, 1915. Applieatiortor reissue filed July 30, 1919. Serial No. 314,384.

To all whom. it may concern:

Be it. known that I, RAYMOND A. HEISING, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Thermionic Voltmeters, of which the followin is a full, clear, concise, and exact description.

This invention relates to apparatus for the measurement of voltage.

Its object is to measure. the voltage between two points of an electrical network without taking power from that network and without introducing frequency errors. A further object is to measure a direct or alternating voltage without the necessity for previous calibration of the instrument, which calibration in the case of high frequency measurements is often unsatisfactory and diflicult.

These objects are accomplished by con necting the input circuit of a thermionic rectifier between the net work terminals across which the voltage is to be measured, and allowing the resulting rectified current in the output circuit to actuate an indicating instrument. a

The nature of thisinvention and its method of use will be more fully explained in connection with the drawing, which represents the circuit arrangement of the invention.

In the drawing, 1 represents a source of voltage to be measured and 2 is a thermionic rectifier of the audion type upon which is impressed the voltage which it is desired to measure. This rectifier consists of a heated v electron-emitting cathode 3, a cool anode 5 and auxiliary electrode 4 usually located between the cathode and the anode. These elements are sealed in a vessel which is 'exhausted as thoroughly as possible so as to remove practically all the gas. The hot cathode gives ofi electrons, which, due to the electric field set up between anode and cathode by means of battery 7, are driven across the evacuated space and strike the anode. A current of electrons therefore flows between these two elements and its circuit is completed externally through the battery and the current indicating instrument 6. This circuit is called the output circuit of the rectifier, and since electrons can pass only from cathode 3 to anode 5 and not in the reverse direction, the current .to change the number of the electrons passing to anode 5, and, therefore, the intensity of the current in the output circuit; further, if the grid is maintained at a lower potential than the cathode, no electrons can flow to the grid and consequently no current can flow in the input circuit which comprises the electrical path 1, 13

(lower), .10, 3, 4, 13 (upper), 1. Under these conditions the input circuit requires practically no power to produce changes in the output current. To maintain the grid at a potential lower than that of the cahode is one function of the battery 8, which in combination with the resistance 9 and contact maker, 10 supplies an adjustable voltage across the input terminals of the rectifier. The intensity of current in the output circuit is determined completely by the voltage impressed upon its input terminals so long as the grid potentialis maintained negative; in particular, if the voltage across the input circuit is made sufficiently large, so as to force a sufliciently large negative charge upon the grid 4, the current in the output circuit may be reduced to zero and thus no indication will appear upon the instrument 6.

These facts furnish the basis of a method for measuring an unknown voltage, either alternatin or direct, without previous calibration o the instrument in terms of a known voltage of the same type. The method of use for this purpose is as follows: The switch 11 is thrown to the. position 12, 12, in which position the input circuit is closed through the conductor 14. The contact 10 is now adjusted until the voltage over the input circuit is just suflicient to reduce the current in the output circuit to zero as indicated by the instrument 6. The switch 11 is next thrown to the position 13, 13, in which position a source 1 of voltage to be measured is connected into the input will, therefore, cause a unidrectionalcurrent to flow in the output circuit once'every cycle and the average value of this current will be indicated by 6. The contact 10 is now moved to some other position 10'. in which 'the outv ut current again falls to zero be'- lcauseo the increase in negative voltage mpresed from battery 8 in the new position of I contact 10. In other words, the increase in I it voltage impressed from battery 8 is just sufli-.

' cient to make. the resultant maximum negaof potential over t tive input voltage the same as inthe case when t the maximum value of the alternating volt.-

' age to be measured. In the practical-use of the device, the resistance 9 should .be marked .ofi in terms of the fall of potential alon its length as in any potentiometer system 0 measurement. 'If a direct voltage is to be measured instead of an alternating one, the

only precaution to be observed is that they are that measurements, 0 alternating volt- ..ages maybemade by a direct current poten- "tiometer 'method, which is of-considerable value in measurements of alternating voltages of high frequency, that the device takes practically no power for its operation, and also that voltages of widely difi'erent frequencies may be measured with the same accuracy. ThlS last statement is sup orted by v the fact that thermionic amplifiers ave been found to ive no noticeable distortion when used in te ephonyor, in radio operation.

-the output circuit of said rectifier, an adjustable source of electromotive force in the input circuit of said rectifier, and terminals for impressing upon said linput circuit a volta e-to be measured.

I 2. n combination, a thermionic rectifier comprising a hot cathode, a cool anode and an auxiliary electrodein an evacuated vessel, a current indicating instrument and a battery connected in series between said anode and said cathode, terminals in the input circuit of said rectifier to which terminals may be a plied a voltage to be measured, and an' a justable source of electromotive force connected, in series with said terminals, between said cathode and said auxiliary electrode.

3. A voltmeter comprising a vacuum tube having input and output circuits, a current indicating instrument in the output circuit of-said vacuum tube, an adjustable source of electromotive force in the input circuit e 'source 1 was not in circuit. Thisincrease in voltage 'measured by the fall.

he resistance 9 between thepoints 10 and 10', is thereforeequal to of said vacuum tube and for'im- I I 4. An" electrical measuring instrument comprising a vacuum tube device havin .a cathode, an anode, a control electrode an a source of space current, means for connecting an electrical source of unknown value to certain of said electrodes, a measuri instrument connected to said device,-aiid means formaking the potential of-said control' electrode suchas to reduce the space current between anode and cathode subpon said input circuit a voltage to bemeasured.

stantially to zero while measurements are I beingkmade whereby substantially no power is ta enf from the unknown source at that time] 5. A voltmeter comprising an electron v discharge device having input and, output circuits, a current indicating instrument in said output circuit, an adjustable source of electromotive force in said input circuit, and

terminals for timpressin on one of said circuits an alternating 'vo tage the peakvalue of which is to be measured."

6 The method of measurin voltage which comgeises applying said vo tage'to a vacuum tu device having a control electrode and an output circuit, applying a known voltage to the control electrode of said device, measuring the combined effect of said voltages in the output circuit of said device, and comparin known voltage and'said efl'ect .witlia previously determined characteristic of said 100 devic 7. The method of measurin voltage the values of said 1 vacuum tube having an output circuit, an

input circuit and aplurality of sources of same efi'ect in said output circuit both when the operation of the tube is influenced and when not influenced by the voltage to. be measured.

8. The method of measuring volta ewhich comprises comparin the grid vo tages necessary to produce t e same effect in the output circuit of a vacuum tube both when the operation of the tube is influenced and when not influenced bythe electrical voltage to be measured;

9. he method of measuring voltage which comprises applying said voltage to a vacuum tube device avlng a cathode, an anode, a control electrode, and a source of space current, and making the potential of said control electrode such as to reduce the.

potential, and comparing the volta es nec- -essary in said input circuit to pro uce the tentials to the input and output circuits of a vacuum tube, noting an electrical efl'ect in said output circuit, applyingsaid alternating current voltage to one of said circuits and comparing an effect produced thereby in said output circuit with said firstmentioned effect. n

11. The method of determining the magnitude of a voltage of an alternating current, which comprises applying steady po- 10 tentials to the input'and output circuits of a vacuum tube, noting an electrical effect in said output circuit, applying said alternating current voltage to said input circuit and comparing an effect produced thereby in 15 said output circuit with said first mentioned efi'ect.

RAYMOND A. HEISING.

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