US2124740A - Electronic indicating device - Google Patents

Description

y 26, 1933- c. N. KIMBALL ET AL ELECTRONIC INDICATING DEVICE Filed Oct. 27, 1957 RESON CE INDICATOR o u o l n o o.

VOLTAGES To 2 BE COMPAR i PM d m Sm, %%////W%//// F Patented July 26, 1938 UNITED STATES PATENT OFFICE ELECTRONIC INDICATING DEVICE of Delaware Application October 27, 1937, Serial No. 171,254

6 Claims.

Our invention relates to electron discharge devices, more particularly to such devices useful as visual indicators of voltage and having a fluorescent electrode which is rendered luminous and has the appearance of a pattern of light which changes in response to the change in the magnitude of the applied voltages, a device of this character being particularly suitable for indicating resonance of apparatus responsive to radio frequency currents and voltages. The present application is a continuation in part of our application, Serial No. 112,462, filed November 24, 1936 and assigned to the Radio Corporation of America.

There has been disclosed, and claimed, in U. S.

Patent 2,051,189 of H. M. Wagner, patented August 18, 1936, an electron ray indicator tube con- Qventionally described as the 6E5 type. Briefly, such a tube comprises an envelope having within it a cathode provided with two emission sections. One of the emission sections is surrounded'by amplifier electrodes comprising a grid and anode and the other is surrounded by the tuning indicator elements. The indicator elements comprise a control electrode and a dish-shaped anode coated on its inner surface with fluorescent material. The control electrode is connected to the amplifier anode, and the amplifier section input electrode or grid is connected to a source of sigrial-derived direct current voltage. When maximum signal is tuned in, the luminous portion of the plate, or target, is of a maximum width. With minimum, or no signal the electronic shadow cast by the control electrode on the coated anode or target is a maximum. In a receiving system equipped with automatic volume control (AVC) the grid of the indicator tube amplifier section is connected to the AVG voltage source.

Such a 6E5 type tube is satisfactory when used in signalling systems producing direct current voltages for the indicator tube input grid which are not in excess of 8 volts. This is due to the sharp cut-off characteristic of the amplifier section of the indicator tube, the amplifier section having a high mu. Hence, when the value of the AVG bias applied to the input grid of a 6E5 tube is in excess of 8 volts, the shadow angle on the target remains closed. There is no further indication of approach to the desired resonance condition of the receiver. To solve this problem the 6G5 type tube was provided. This tube differs from the 6E5 type only in that it is provided with a remote cut-ofi input grid. However, while permitting the tube to be used in receiving circuits with AVC voltages in excess of 8 volts, the change in shadow angle with grid bias is small at low AVC voltages.

A tube of this same type would be desirable as a balance indicator or as a comparison device for 5 comparing the voltage or current conditions in two different circuits. Previous balance indicators have usually required the use of two separate meters or indicators connected in different circuits requiring duplication of instruments and 10 circuits. In such an arrangement, due to the bulk of the measuring instruments, vision must be shifted from one indicating device to another, increasing the possibility of errors of comparison.

Accordingly, it is one of the principal objects 15 of this invention to provide an electron discharge device of the type described capable of functioning as a reliable indicator of a wide range of input direct current voltages.

More specifically an object of the invention is 20 to improve electron discharge devices of the type adapted to produce an electron shadow of varying width as the magnitude of the direct current voltage input varies; the improvement comprising independent high mu and low mu amplifier 25 sections constructed and arranged to produce opposed shadows on the target, and which shadows successively become narrow as the input voltage varies over a wide range of values.

Another object of my invention is to provide an 30 electron discharge device of the'type described which can function as a comparison device or balance indicator for indicating variations of current or voltage in two circuits to be compared, the improvement comprising independent electrode structures arranged to produce opposed shadows on the target, the difierence in the shadows or the absence or presence of shadows indicating balance or unbalance of the circuits being compared. 40

Other objects of the invention are to improve generally the eificiency and utility of electron discharge devices of the type described.

The novel fwtures which we believe to be characteristic of our invention are set forth in par- 45 ticularity in the appended claims; the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in-which we have 50 indicated diagrammatically a circuit organization whereby our invention may be carried into efiect.

In the drawing:

Figure l is a circuit'diagram of a portion of a receiving circuit and schematic diagram of an 5 electron discharge device embodying the invention.

Figures 2a, b, c and 11 show the successive appearance of the indicator face of the target as the AVG voltage varies in magnitude.

Figure 3 is a schematic section of a modifiication of an electron discharge device made in accordance with my invention, and

Figures 4a, b and 0 show the appearance of the indicator face of the target under difierent conditions when used as a balance indicator or comparison device.

In the circuit shown in Figure 1 a diode detector, or rectifier, i has its anode 2 and cathode 3 connected to opposite sides of the secondary winding 5 of the double tuned transformer 5. The primary circuit 6, as well as the secondary circuit 5, is tuned to the operating I. F., assuming the detector is used in a superheterodyne receiver. The usual networks are employed in the latter, 1. e., a tunable radio amplifier, a tunable first detector, a tunable local oscillator and one, or more, I. F. amplifiers. The customary uni-control tuning adjusting means will be used for varying the rotors of the variable tuning condensers, and the circuit 6 is to be understood as being in the plate circuit of the last I. F. amplifier tube. These networks are not shown since those skilled in the art are fully aware of the construction thereof.

The diode circuit includes resistor I, shunted by I. F. bypass condenser 8. The grounded cathode 3 is connected to the low alternating potential side of input circuit Q through the resistor i. The audio voltage component of detected 1. F. current is impressed on one, or more, audio amplifiers by means of the adjustable tap 9 and audio coupling condenser ID. A reproducer of any desired type follows the last audio amplifier. The direct current voltage component of detected I. F. current is employed for automatic volume control (AVC) of the pre-second detector stages. as, for example, the radio and I. F. amplifiers. The AVC lead is connected to the anode side of resistor i through filter resistor H, and bypass condenser l2 to ground. The network Hl2 is given the proper time constant to permit the AVG circuit to compensate for carrier fading efiects.

In the embodiment of my invention shown in Figure 1, the tuning indicator tube comprises an envelope 13 within which are disposed the electrodes of the indicator section, and the high and low mu direct current amplifier sections. The tube is schematically represented since its detailed constructional features are shown in the Wagner patent referred to above. Those skilled in the art will readily be able to construct a tube embodying the present invention by modifying the tube of said Wagner patent in the light of the present teachings.

The tube is provided with a cathode l3 of the conventional, indirectly-heated, equipotential type; a grid It is concentric, and almost co-extensive, with and surrounds the cathode. A pair of anodes l5 and I6, of the same diameter, are co-axially arranged in spaced relation and surround the grid Hi. The anodes I5 and I6 are substantially co-extensive with the cathode H3. The portion of grid It lying between cathode l3 and anode l6 has at least one turn less than the grid portion between anode l5 and cathode l3. By way of illustration it will be seen that there are five grid turns between anode l5 and cathode i3, whereas only four grid turns are provided hetween cathode i3 and anode it. The control grid it is wound with a continuous pitch, turns being removed from one end to impart a lower mu to that section of the grid. Hence, it will be seen that a pair of triode sections are provided, one having a higher 'mu than the other.

The cathode i3 is extended upwardly and provided with a second emitting section H. A second separate cathode unit could be used. A pair of similar control electrodes I8 and it are disposed on opposite sides of emission section ii. The electrodes iii-48' may be rods, or vaneshaped sheet material placed edgewise to the cathode H. Surrounding and concentric with the emission section H is an anode i9 shaped like a dishpan having a coating 2t on its inner inclined face; the coating material being fluorescent under electron bombardment. An aperture is provided in the base of the anode or target 89 to permit the emission section I! and electrodes l8|8' to be positioned at the axis of the anode.

The electrode [8 is connected by lead 2! to plate l5, while electrode It is connected to plate 46 by lead 22. Electrons emitted from section II, and striking coating 26 with sufiicient velocity, cause it to fluoresce. A cap (not shown) is usually provided over the top end of cathode section I! to confine electron action, and to act as 'an electrostatic shield against stray charges on the glass envelope. The electrons travel radiall outwardly from the cathode I! to the coating 20 in a wide beam. The extent of the anode surface reached by the beam is determined by the direct current voltages on control electrodes Ill-I8. Two separate luminescent portions will be obtained when the receiver is oil tune. The pattern of light will extend around the entire circumference of anode l9 when the receiver is tuned to resonance.

The control electrodes l8l8' are at positive potentials with respect to cathode II. This is accomplished by connecting plates l5 and Hi to a source of positive direct current voltage; resistor 23 connecting plate IE to the positive terminal of the voltage source, and resistor 26 connecting plate IE to the said terminal. The cathodes l3 and I! are at ground potential, and fluorescent anode i9 is connected to the positiveterminal of,the direct current voltage source. A direct current connection establishes control grid l4 at the potential of the anode side of resistor I. Thus, the AVG bias varies the potential control grid I 4, and hence the potentials of control electrodes l8--l8'.

In the absence of received signals there is no AVC bias produced, since the detector I does not produce detected signal currents. In that case, the control grid 14 will be substantially at the potential of cathode l3, and the current flow through the high and low mu sections will be a mwmum. This means that the voltage drops across resistors 23 and 24 will be a maximum,

and, therefore, control electrodes l8 and I8 will be at minimum positive potential with respect to grounded cathode Ii. As a result of this low positive bias on both control electrodes, electrons will be repelled from the latter, and the pattern shown in Figure 2a will be formed on the coating 20.

The shaded areas in Figure 2a represent the luminous areas, while the blank areas denote shadows. Electrode l8 produces the so-called high mu shadow since this electrode varies in bias with space current variation in the high mu triode section of the tube; electrode it produces the "low mu shadow since it responds in bias to the space current change in the low mu triode section. Figure 2a, further, shows the appearance of anode I! when viewed from the right side oi. the tube in Figure 1. The dark, or shadow, spaces are depended upon to indicate resonance conditions of the receiver.

Assume, now. that weak signals are received, and a small amount of AVG bias is generated. The space current flowing through the high mu section of grid will be reduced immediately. The shadow angle of the high mu shadow on anode l9 begins to close. At some low bias (-5 to 8 volts) determined by the pitch of the high mu grid, the shadow angle becomes zero. This condition is shown in Figure 2b. Up to this point only a small change in the angle of the low mu 7 shadow has" taken place.

Further increase in AVC bias causes the shadow angle of the low mu section to close. Figure 2c shows the appearance of the anode l9 when the low mu shadow is near cut-off. The bias at which the low mu shadow angle is zero can be made equal to -30 to -40 volts depending upon the maximum AVC voltage available. Figure 2d shows the latter condition. Accordingly, it will be seen that the indicator tube of the present invention is capable of responding to a relatively wide range of AVG voltages,-and that this is done with a single tube construction.

By proper choice of the structural dimensions of the tube and triode section plate loads, conditions can be adjusted so as to cause the two shadows to respond to any reasonable AVC voltage ranges. Of course, Figure 2a shows the appearance of the tube when ofi tune, or when very weak carrier is being received. Figure 2d, on the other hand, shows the tuning indicators appearance when the receiver is exactly tunedto a strong incoming carrier. Intermediate conditions are shown by Figures 2b and 20.

In Figure 3 the electron discharge device is provided with the two-section cathode i3 surrounded by anodes I5 and i6 axially displaced along one emitting section of the cathode and connected to the control electrodes l8 and I8 positioned between the other section of the oathode l3 and the fluorescent target or anode IS. The indicator and amplifier sections could be made as separate units each having its own cathode. In accordance with my invention each of the anodes l5 and it has positioned between it and the cathode a separate control grid 25 and 26. Difierence in potential between the control electrodes i8 and i8 and the fluorescent anode is produced in the same manner as in the device shown in Figure 1 by means of the drop in the resistors 23 and. The grids 25 and 26 may have the same pitch, or, if desired, different pitch.

The voltage sources to be compared are connected to the leads 21 and 28 connected to the separate grids 25 and 26. The tube functions in substantially the same way as that shown in Figure 1. The difference in the circuits being compared is indicated by a. difference in the shadows formed on the fluorescent target by the control electrodes l8 and 18'.

The applications of a tube of this type are numerous. In use as a balance indicator. the tube is'operated'with both grids biased to cut-ofl at balance. The whole target under this condition fluoresces. The change in bias on either of the two grids and the formation and size of which the balance is off. One specific applicathe proper polarity to the grids of the tube. Thus,

when the plane is on the course no shadow appears. This condition is shown in Figure 4a. If the planedrifts to the left a shadow appears as indicated in 4b on the left hand side of 'the target, and if it drifts to the right a shadow appears on the right hand side of the target as indicated in lo, the size of the shadow being proportional to the amount the plane is off its course.

While we have indicated and described a systern for carrying our invention into effect, it will be apparent to one skilled in the art that our invention is by no means limited to the particular organization shown and described, but that many modifications may be made without departing from the scope of our invention, as set forth in the appended claims.

What we claim as new is:

1. An electron discharge device having an envelope, a cathode within said envelope for supplying electrons, a dish-shaped anode surrounding" the cathode and having its interior surface coated with a fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a plurality of control electrodes positioned between the anode and the cathode to determine the area of the fluorescent surface of the anode reached by the electrons, a second cathode in said envelope, a plurality of plates surrounding said second cathode,

said plates being axially spaced along said second cathode, and control means between the second cathode and said plates and a conductor connected between each of the control electrodes and a different one of said plates.

2. An electron discharge device having an envelope, a cathode within said envelope for supplying electrons, a dish-shaped anode surrounding the cathode and having its interior surface coated with fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a pair of oppositely disposed control rods positioned between the coated anode and the cathode to determine the area of the fluorescent surface of the anode reached by the electrons, a second cathode, a pair of plates surrounding the second cathode and axially spaced with respect to each other, control means positioned between the plates and the second cathode, each of said plates being connected to a difierent one of said control rods.

3. An electron discharge tube having an envelope, a cathode within the envelope for supplying electrons, a dish-shaped anode surrounding the cathode and having its interior surface coated with a fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a control electrode positioned between the anode and the cathode to determine the area of the fluorescent surface of the anode reached by the electrons, a second control electrode positioned on the opposite side of the cathode, a second cathode, a grid surrounding the second cathode, a pair of plates surrounding the grid, the plates being of the same diameter and being coaxially spaced, the grid portion between one of the plates and the second cathode having a lesser number of nuns than its other portion, and independent direct current connections between the two control electrodes and said plates.

4. An electron discharge device having an envelope, a cathode within said envelope for supplying electrons, a dish-shaped anode surrounding the cathode and having its interior surface coated with fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a plurality of control electrodes positioned between the anode and the cathode to determine the area of fluorescent surface of the anode reached by the electrons, a second cathode, a plurality of separate grids axially spaced with respectto each other and surrounding said second cathode, a plate electrode surrounding each of said grids and independent direct current connections between each of the plates and a diflerent one of said control electrodes.

5. An electron discharge device having an envelope, a cathode within said envelope for supplying electrons, a dish-shaped anode surrounding the cathode and having its interior surface coated with fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a pair of control rods-disposed on opposite sides of said cathode and between said cathode and the anode to determine the area of the fluorescent surface of the anode reached by the electrons, a pair of grids surrounding said cathode and axially spaced with respect to each other and said anode, a plate surrounding each grid, each plate having a direct current connection between a diiierent one of said control rods.

6. An electron discharge device having an envelope, a cathode within said envelope, a dishshaped anode surrounding the cathode and having its interior surface coated with fluorescent material for receiving electrons from the cathode to produce a luminous annular shaped pattern on the anode, a plurality of control rods positioned between the anode and the cathode and parallel to the cathode to determine the area of fluorescent surface of the anode reached by the electrons, a plurality of separate grids axially spaced with respect to each other and surrounding said cathode, a plate electrode surrounding each of said grids and independent direct current connections between each of the plates and a different one of said control rods.

CHARLES N. ALL.

' EDWARD W. Y.

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