US3197673A - Counting circuitry employing multicathode glow transfer tube and a. c. bias source to increase circuit stability - Google Patents

Description

July 27, 1965 C. B. FALCONER COUNTING GIRGUITRYv EMPLOYING MULTI-CATHODE GLOW TRANSFER TUBE AND A.C. BIAS SOURCE TO INCREASE CIRCUIT STABILITY Filed Oct. 4, 1962 D. c. VOLTAGE SOURCE l 1 u /4 E --1 R D FIG.

H% T? I FIG.2

INVENTOR CHARLES B. FALCONER BY WW,

ATTOR N EYS United States Patent C) V v p, 3,197,673 COUNTING CIRCUI'I'RY EMPLOYING MULTL CATHODE GLOW TRANSFER AND A.-C. BIAS 'SOURGE TO INCREASE CIRCUIT STABILITY Charles B. Falconer, Newton, Mass, 'assi'g'n'or to Laboratory for Electronics, Inc., Boston, Mass, a corporation of Delaware 7 H Filed Oct. 4, 1962, Ser. No. 228,385 2 Claims. (Cl. 315 84.6)

This invention relates in general to gas discharge tubes and in particular to'a new and improved'technique for increasing the reliability and stability of counting circuits which include glow transfer tubes.

Many of the commonly'used counting'circuits employ glow transfer tubes as their basic counting element. In such a tube, a glow discharge occurs between -a central anode and one of several cathodes, usually ten, which encircle the anode. By the application of a sequenceof pulses for each count, the discharge is transferred to the next adjacent cathode. The current surge arising from each such discharge flows through a cathode resistor which must develop a voltage sufiicient to operate the following circuits. If the voltage developed across the cathode resistor is to large, instabilities arise in the glow transfer tube and cause the discharge to jump spuriously from one cathode to another. In a counting circuit such transfer errors can be extremely serious. This problem is felt most acutely in readout circuits which employ, in addition to the glow transfer tube, a series of individual gas discharge tubes, such as neon lamps, in the cathode circuits of the glow transfer tube to indicate the position of the count. An example of such a circuit may be seen in Patent No. 2,985,794, issued to E. R. Sarra'tt on May 23, 1961.

Although a bias is usually applied to place the neon lamps near their maintaining potential, the voltage developed across the cathode resistor of the 'glow discharge tube must still be sufii-ciently large to reach the striking potential of the neon lamp in order to turn it on. At the same time, this voltage must be kept sufiiciently low so that instabilities and spurious transfers do not occur in the glow transfer tube. Since the D.C. bias of the neon lamps must be kept below the minimum maintaining potential and the voltage developed across the oathode resistor of the glow transfer tube plus the D.C. bias must reach the maximum striking potential of all the neon lamps in the set, the neon lamps must be closely matched with each other so that the required voltage swing may be minimized. While, in some cases, a matched set of neon lamps may be obtained, which does allow the voltage swing to be kept within reasonable limits, such a set is extremely costly. In addition, there are usually six decades, that is, six glow transfer tubes each with associated circuitry including a "series of neon lamps in a counting circuit, and hence the problem of matching each set to every other set is encountered, thereby greatly increasing the rejection rate and the overall cost.

It is, therefore, a primary object of the present invention to provide a new and improved technique whereby the signal voltage developed across each cathode resistor in a glow transfer tube circuit utilizing neon lamps may be reduced, thereby eliminating the possibility of spurious transfers.

It is another object of the present invention to reduce the necessary D.C. voltage swing between the minimum maintaining potential and the maximum striking potential in a group of neon lamps, thereby resulting in a lower rejection rate.

It is a further object of the present invention to provide means for reducing the signal voltage necessary to operate a gas discharge tube.

Broadly speaking, the resent invention provides for the application'of a continuous AC. voltage to'theiieon lamps in the readout circuit of a glew transfer tube. Under these conditions, the maximum ]).(3. voltage needed to turn the neon lamps on is considerably lower and the minimum D.C. voltage 'Will "allow the neon lamps to turn off is now higher. Under these circumstances, the diiference between the two voltages, ie. the D.C. voltage signal which must be applied,- is reduced, with "consequent increase in circuit stability. Within ee'n tain limitations, this reduction may'beshovvn to be equal to the peak to peak value of the AC. voltage.-

These and other objects of the present invention to gether with further features and advantages thereof 'will become more apparent from the -fellov'v'ing detailed description in which: M V q I FIG. '1 diagrammaticany illustrates a typical embodiment of the present invention; and

FIG. 2 illustrates graphically the 'etfect'of theAQ. bias on the voltages required to drive a gasdischa'rge tube.

In specific reference to FIG. 1, a glow transfer tube 10' is shown having therein an anode 12, a series of cathodes 14, and a series of guides '16 and It? actuatedjby a ulse circuit '15. The anode 12 is connected to a'eonstant high DE. voltage source 20 through the anode resistor 21. The cathode resistors 22 are connected in parallel to ground, While each of the cathodes 14 has a neon lamp 24 connected thereto. All of the neon lamps 24 are connected in parallel to a D.C. bias source 26 which places them at a preselected potential. In addition to the D.C. bias source 26, an AC. voltage source 28 place'sjan;

A.C. voltage bias on each one of the neon lamps 24; the AC. source 28 may be, for example; a sine wave generator which modulates the DI). bias.

The effect of the A.c. voltage source as 0a the Inagnn tude of the DC. voltages needed to rive the neon lamps 24 is shown in FIG. 2. ,The minimum ni'ain'tfainingpotential for a group of rie'o i lamps is designated as e While the maximum maintaining potential is designated as e Similarly, the minimum striking potential is designated as e while the maximum striking potential is designated as e It is seen that for reliable neon operation, i.e. to ensure that all the neon lamps 24 will be turned off and on, a D.C. voltage swing D is required which is equal to e.; (e d) where d is a voltage increment of sufiicient magnitude below the maintaining potential to extinguish the discharge. If, however, the applied D.C. drive voltages are modulated by an AC. voltage with a peak to peak value of 2B, all the neon lamps 24 are turned off when the D.C. drive voltage is equal to (e d) +E) since on some portion of the negative half cycle of the AC. bias the drive voltage falls below the minimum maintaining potential 2 Such a minimum drive voltage is designated as 2 on the graph in FIG. 2;

the D.C. bias is, in practice, set at this level. Similarly,

all the neon lamps 24 are turned on by a drive voltage of e -E, since on some portion of the positive half cycle of the AC. bias the drive voltage is equal to the maxi mum striking potential. Such a maximum drive voltage is designated as e It is seen, therefore, that the new re quired voltage swing D is equal to e -e which is equal Ifatented 'July 27, 1965.

turned off during the negative half cycle of the AC. bias With drive voltage e on, it is necessary that e 2E (or e E) be greater than e d. This imposes the limitation that 2E must be less than e -(e d). These conditions impose a maximum limitation on the peak to peak value of the AC. voltage. However, the DC. voltage swing required is still reduced by a significant factor. In a typical case, a voltage swing of 30 volts is reduced to 15 volts by use of the AC. bias with a peak to peak value of 15 volts.

The AC. voltage in the present invention may merely be taken from a line current of 60 c.p.s. Although all the neon'lamps may not strike (or turn off) in succession at such a frequency, when the counting circuit is stopped to take a reading, the proper neon lamp will light in less than 17 milliseconds (and any other improperly lit neon lamp will be extinguished). The fact that all the neon lamps do .not light (or turn off) in succession is far overshadowed by the significant increase obtained in stability and reliability of proper transfers in the glow transfer tube. Moreover, the human eye does not tend to differentiate such a rapid succession of individual lamps if all were to light consecutively during the counting phase.

' While the use of the AC. biasing arrangement has been illustrated in a circuit for a glow transfer tube, nonetheless such a bias can be used in any circuit which requires that gas discharge tubes be turned on and or: with a minimum voltage swing. In addition, it is not necessary that a DC. bias voltage accompany this A.C. bias. Since, in this latter case, the gas discharge tubes are usually turned off by dropping the applied voltage to zero potential, the DC. voltage swing is reduced only by a factor of E. It should also be noted that the use of this technique need not be restricted to gas discharge tubes; it can be applied to any non-liner device which has a negative incremental resistance, AR, shortly after the initial rise of its operating curve; many such devices are formed in the semiconductor field, such as tunnel diodes (where the voltage changes discontinuously with small current changes) and certain types of transistors.

Having described the invention, it is apparent that numerous modifications and improvements may be made by those skilled in the art, all of which fall within the scope of the invention; therefore, the invention herein disclosed should be construed to be limited only by the spirit and scope of the appended claims.

What is claimed is:

1. An improved counting circuit in which a glow discharge is sequentially transferred from one adjacent cathode to the next in a glow transfer tube by a series of applied impulses comprising: a series of gas discharge tubes each connected to one of said cathodes; means for sequentially applying a drive voltage to saidgas discharge tubes in response to said glow discharge; and means for applying a continuous A.C. voltage to each of said gas discharge tubes to reduce the magnitude of the drive voltage necessary to reach the maximum striking potential of said gas discharge tubes, said continuous AC. voltage having a peak to peak value less than twice the minimum striking potential of said gas discharge tubes and not greater than the difference between the maximum striking potential and the maximum maintaining potential.

2. An improved counting circuit in which a glow discharge is sequentially transferred from one adjacent cathode to the next in a glow transfer tube by a series of applied impulses comprising: a series of gas discharge tubes each connected to one of said cathodes, said series being characterized by having a maximum and minimum striking potential and a maximum and minimum maintaining potentiial; means for sequentially applying a drive voltage to said gas discharge tubes in response to said glow discharge; means for applying a D.C. bias to each of said gas discharge tubes, said DC. bias having a preselected value not less than the minimum potential required to maintain a discharge in said gas discharge tubes; and means for applying a continuous AC. voltage to each of said gas discharge tubes, said continuous AC. voltage having a peak to peak value not greater than the difference between said minimum striking potential and said minimum maintaining potential and not greater than the difi'erence between said maximum striking potential and said maximum maintaining potential.

References Cited by the Examiner UNITED STATES PATENTS 2,920,239 1/60 Saeger 3l5-l76 2,985,794 5/61 Sarratt 315-845 ARTHUR GAUSS, Primary Examiner.

Claims (1)

1. AN IMPROVED COUNTING CIRCUIT IN WHICH A GLOW DISCHARGE IS SEQUENTIALLY TRANSFERRED FROM ONE ADJACENT CATHODE TO THE NEXT IN A GLOW TRANSFER TUBE BY A SERIES OF APPLIED IMPULSES COMPRISING: A SERIES OF GAS DISCHARGE TUBES EACH CONNECTED TO ONE OF SAID CATHODES; MEANS FOR SEQUENTIALLY APPLYINGG A DRIVE VOLTAGE TO SAID GAS DISCHARGE TUBES IN RESPONSE TO SAID GLOW DISCHARGE; AND MEANS FOR APPLYING A CONTINUOUS A.C. VOLTAGE TO EACH OF SAID GAS DISCHARGE TUBES TO REDUCE THE MAGNITUDE OF THE DRIVE VOLTAGE NECESSARY TO REACH THE MAXIMUM STRIKING POTENTIAL OF SAID GAS DISCHARGE TUBES, SAID CONTINUOUS A.C. VOLTAGE HAVING A PEAK TO PEAK VALUE LESS THAN TWICE THE MINIMUM STRIKING POTENTIAL OF SAID GAS DISCHARGE TUBES AND NOT GREATER THAN THE DIFFERENCE BETWEEN THE MAXIMUM STRIKING POTENTIAL AND THE MAXIMUM MAINTAINING POTENTIAL.

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