US2536497A

US2536497A - Operating voltage supply arrangement for cathode-ray tube apparatus

Info

Publication number: US2536497A
Application number: US748430A
Authority: US
Inventors: Forbes Ian Stuart; Harrod Kenneth William George
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1946-05-20
Filing date: 1947-05-16
Publication date: 1951-01-02
Anticipated expiration: 1968-01-02
Also published as: GB614557A

Description

Jan. 2, 1951 Filed May 16, '1947 s. FORBES ET AL ,536,497 OPERATING VOLTAGE SUPPLY ARRANGEMENT FOR CATHODE-RAY TUBE APPARATUS 2 Sheets-Sheet 1 1 Tvm SUPPLY 1 Q 2a, JY/vc. M0701? GONIOML-IM SIGN/71. GEN.

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dllllF STABZ/ZED POWER 184 Y TUBE SUP/L Y milk INVENTOR.

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[an Saar! f'orbes S- AZmneib Wl/iam Gaol-ye flqz'rod ATTORNEY Patented Jan. 2, 1951 OPERATING VOLTAGE SUPPLY AR- RANGEMENT FOR TUBE APPARATUS CATHODE-RAY Ian Stuart Forbes, Chelmsiord, and Knneth William George Harrod, Little Baddow, England,

assignors,

by mesne assignments, to Radio Core poratlon of America, New York, N. Y., a corporation of Delaware Application May 16, 1947, Serial No. 748.430

' In Great Britain May 20, 1946 Claims. (Cl. 343*118) This invention relates to operating voltage supply arrangements for cathode ray tube apparatus and more particularly to such apparatus of the kind in which a cathode ray tube is employed in functional corelationship with a motordriven moving member, so'as to display, indicate or measure signals which are expected to vary as said member is moved. An example of this kind of apparatus is provided .by radio direction finders of the spinning radio goniometer or spinnin aerial type, wherein a motor driven directional aerial is continuously rotated and the signals derived therefrom displayed by means of a cathode ray tube subjected to deflection control by a time base circuit synchronised with the aerial rotation. Another example of apparatus of the kind referred to is provided by oscilloscope apparatus employed for taking heat engine indicator diagrams, against a base line which-should correspond to piston displacement. In such a case if the engine run at varying speed the diagram will not be of constant length a as is desired for ease of subsequent calculations. There are numerous other examples of cathode ray tube apparatus wherein the time deflection of the tube is required to be accurately co-related with the movement of a driving memher which in the case of the direction finder mentioned is the rotating aerial and in the case of an engine indicator diagram apparatus is a moving part of the engine.

The importance of maintaining constant operating voltages to cathode ray tubes employed in apparatus of the kind referred to is in general well recognised and it is common practice to provide stabilised voltage supplies to the various electrodes of the tube, as well as to amplifier deflection circuits and the like associated therewith. It has now been found, however, that despite the provision of careful stabilisation of voltage supply comparatively serious errors can occur by reason of variation in speed of the driving member due to variation in frequency of an alternating current supply employed to energise a motor driving said member. The magnitude and importance of the errors which may occur may be exemplified by taking the case of a radio direction finder of the spinnin radio goniometer type, wherein the aerial is rotated by an A. C. motor supplied from A. C. mains. If the frequency of the supply changes by 5%, the result of the consequent changes in the speed of the motor may produce a bearing error of the order of 9 degrees. The present invention 'seeks to obviate this type of diiiiculty and reduce the corresponding errors to small proportions.

According to this invention a cathode ray tube apparatus of the kind referred to is characterised in that the time base or deflection control of the tube is subjected to corrections in dependence upon departures from a predetermined value of the speed of a motor driving the associated moving member, so as to correct for or substantially reduce variations in indication or measurement which would otherwise result from said departures.

The invention is illustrated in the accompanying drawings which show two embodiments in block diagram form. The same references are used for like parts in both figures in which electrical energy supply paths are represented by single lines with arrow heads thereon and mechanical drives are represented by shafts with arrow heads adjacent them.

Referring to Fig. 1 which shows in block diagram form one embodiment of this invention as applied to a radio direction finder of the spinning radio goniometer type a mains or other A. C. supply connected at I is utilised to drive a motor 2, for example an induction or a synchronous motor, the shaft 2a of which mechanically drives the spinning directional aerial or radio goniometer unit 3 and also mechanically drives a source 4 of pulsed or other synchronising signals for the cathode ray tube. The unit 3 includes any well known suitable equipmentpreferably a radio-goniometer-giving an electrical output which varies with the position of the rotating parts, which variation it is required to observe. Since the motor 2 is of the synchronous or induction type its speed will be dependent on the Supply frequency, but substantially independent of the supply voltage. Electrical output from the synchroniser 4 is taken to a shaping circuit or converter 5 or other device which converts the said output into a wave shape suitable for application to a time base circuit 6. The converter 5 receives its electrical power supplies from a stabilised voltage source 1 fed from the main supply. This stabilised voltage source 1 also supplies electrical power to the time base circuit 6. The mains or other A. C. supply from I is also passed through a frequency discriminator circuit 8 which in turn feeds through a suitable voltage supply unit 9 to the time base circuit 6. The voltage supply to the time base circuit 6 through the channel 8-9 determines the velocity of the time base sweep and since the said channel includes the discriminator circuit 8 the voltage supplied therethrough' will vary according to the frequency. The supply unit 9 is such that its output varies according to its own input voltage,

but is substantially independent of its own input frequency and since this input voltage is caused by the discriminator circuit 8 to be a function of the frequency receive the required correctin voltage. The said time base circuit 6 supplies one input to the deflection amplifier circuits at H) which receive a second input from the spinning aerial, or radio goniometer unit 3. The output from unit I is fed to the deflection means (electrostatic plates or the like) of the cathode ray tube II. The deflection amplifier l0 receives stabilised power from-a unit l2 energised from the mains or other supply and the various cathode ray tube electrodes also receive stabilised power as required through a similar unit l3.

It has been found that with an arrangement as just described a variation in frequency of as much as 10%, even when combined with voltage changes of the same order in any combination,

do not produce bearing errors in excess of one degree.

In the modification shown in Fig. 2 the frequency discriminator 8 (which may be, as in Fig. 1 a fiux regulated stabilising transformer whose output is substantially independent of input voltage but dependent only on input frequency and which is arranged in known manner to provide an oulput which varies linearly with input frequency over a wide only to unit I but also to the units 9 and I3. The former unit 9 may be a rectifier providing D. C. supply at, for example, about 1000 volts, to the time base charging circuit 6 the actual voltage, of course, depending on the input frequency to unit 8. The said unit 9 also supplies'voltage to the deflecting amplifier circuits at I0 and to the tube at H. In this case the deflecting amplifiers are so designed that their sensitivity is substantially independent of supply voltage. The output from unit 1 which may, for example, be a rectifier giving a stabilised voltage of approximately 200 volts D. C. feeds units and 6 as in Fig. 1 am also supplies voltage to unit 10. In Fig. 2 an an. plifier I4 is shown interposed in the feed from unit 3 to unit "I.

The actual voltage values required will varyfrom case to case and depend upon design details. In general, however, about 2000 volts negative will be required for the cathode ray tube at H; about 1000 volts positive for the deflection amplifier circuits at ID, the final anode of the cathode ray tube at H and for the usual resistancecapacity circuits in the time base at 6; and additional supplies at about 250 volts and 500 volts positive for other operating potentials in the deflection and other amplifiers.

Although an important application of the invention is to radio direction finders this is not the only application and the said invention may be employed in any cathode ray app ratus of the kind referred to.

Having now particularly described and ascertained the nature of our said invention and in from I the time base 6 will range) provides input not what manner the same is to be performed we deby said shaft to provide further signals whose phase relationship to said timing signals is to be indicated, a cathode ray oscilloscope, means for deflecting the cathode ray beam of said oscilloscope along one axis in response to said further signals, a time base signal generator responsive to said timing signals to deflect said beam along another axis, and means responsive to the speed of said shaft to control the amplitude of the output of said time base signal generator.

2. The invention as set forth in claim 1, wherein said motor is an alternating current motor driven from an alternating current supp and the amplitude of said time base signal varies according to the departure of the frequency of said supply from a predetermined frequency.

3. A radio direction finder system including a goniometer, a motor coupled to said goniometer, and rotating at a speed which is nominally constant but is actually subject to variations, a cathode ray oscilloscope, means for deflecting the cathode ray beam of said oscilloscope in response to the output of said goniometer, a synchronizing system generator coupled to said motor and driven thereby to provide timing signals, a time base signal generator responsive to said timing signals to deflect said cathode ray beam along a second axis, and means responsive to the speed of said motor to control the amplitude of the output of said time base signal generator.

4. An indicator system including a shaft, an alternating current supply, and an alternating current motor rotating said shaft at a speed which is nominally constant but is, subject to variations owing to variations in the frequency of said supply, a device driven by said shaft to provide signals whose phase is to be indicated, a cathode ray oscilloscope, means for deflecting the cathode ray beam of said oscilloscope along one axis in response to said signals, a synchronizing signal generator providing timing signals whose frequency varies with variation in the frequency of said alternating current supp a time base signal generator responsive to said timing signals to deflect said cathode ray beam along another axis, and means responsive to the frequency of said alternating current supply to control the amplitude of the output of said time base signal generator.

5. The invention as set forth in claim 4, wherein said last-mentioned means includes a discriminator producing an, output voltage which depends upon the input frequency over a predetermined range and is substantially independent of input voltage over said range, and means supplying said output voltage to said time base signal generator.

IAN STUART FORBES. KENNETH WILLIAM GEORGE HARROD.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,180,365 Norton Nov. 21, 1939 2,170,847 Banks Aug; 29, 1939 2,222,943 George Nov. 26, 1940 2,233,374 Johnske et al Feb. 25, 1941 2,369,631 Zanarini Feb. 13, 1945 2,408,041 Busignies Sept. 24, 1946 FOREIGN PATENTS Number Country Date 577,795 Great Britain May 31,1946 601,655 Great Britain Mayll, 1948