US2547217A - Circuit arrangement for counting pulses - Google Patents

Description

April 3, 1951 P. J. KRAAYEVELD CIRCUIT ARRANGEMENT FOR COUNTING PULSES Filed Sept. 30, 1948 2'0 INVENTOR.

PIET E12 JOHANNESIQAAYFVELD a, pm, 7 w

' AGENT Patented Apr. 3, T951 CIRCUIT ARRANGEMENT FOR COUNTING PULSES Pieter J ohannes-Kraayeveld, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, 001111., as trustee Application September 30, 1948, Serial No. 52,004 In the Netherlands October 8, 1947 6 Claims.

For countingand dividing periodic or statistic divided pulses, such as occur for example in Geiger-Muller counters, by any number it is hitherto common practice to use circuit-arrangements, in which a division by 10, for example, requires a great number of electric discharge tubes.

The invention has for its object to provide a circuit-arrangement in which this number of required discharge tubes is materially reduced.

The circuit-arrangement according to the invention exhibits the feature that the pulses to be counted are fed to a pulse generator which produces pulses at a frequency which varies With the control-grid bias voltage of a discharge tube included in said pulse generator, the output circuit of which pulse generator comprises a filter network, a higher harmonic of the pulse frequency which is associated with a definite control-grid bias voltage being selected, and a direct voltage being taken from the outputof this filter network which voltage serves as the control-grid bias voltage for the discharge tube of the pulse generator.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which Fig. 1 shows the circuit-arrangement of a blocking oscillator,

Fig. 2 shows, by way of example, a circuitarrangement according to the invention, and

Fig. 3 is a view of the voltages occurring in the circuit-arrangement shown in Fig. 2.

The operation of the blocking oscillator shown in Fig. 1, which comprises a discharge tube I, the parallel combination of a resistance 2 and a condenser 3 and also a coupling transformer 4 between anode and control-grid circuits may be considered as sufiiciently known of itself.

However, inview of the explanation given hereinafter, it should be noted that the width of the pulse produced by such a pulse generator is largely determined by the construction of the transformer 4, whereas the pulse frequency is primarily determined by the time constant RC of the parallel combination 2, 3 and any controlgrid bias of the tube I.

The occurrence of a pulse across the anode circuit of the tube I has the effect of charging the condenser 3 to a definite voltage V of such polarity that the tube I is cut off. This voltage exponentially decreases across the resistance 2 and as soon as the cutting-off point of the anodecurrent grid-voltage characteristic curve is reached, the tube becomes conducting.

2 If with the use of a battery 5 and a potentiometer 6 a positive bias voltage is fed to the control-grid of the tube the said cutting-off point is reached sooner. A positive grid bias voltage consequently results in an increase in pulse frequency. I

This feature of the pulse generator is utilized in the circuit-arrangement according to the invention.

As shown in Fig. 2, the 'output circuit of the tube I has included in it, via a transformer I, a filter network 8. This network is proportioned in such manner that only a definite harmonic, for example, the thirtieth of the pulse frequency produced by the pulse generator at a definite control-grid bias voltage, say, zero volts, is allowed to pass.

If the control-grid bias voltage of the tube I is increased, pulses of higher pulse frequency are produced, but since the networkB gives passage to a definite frequency range only and hence the output of this network will invariably have produced across it a voltage of equal frequency, this frequency does not correspond with the thirtieth harmonic, but with a lower harmonic, for example the 29th of the higher pulse frequency occurring by now. As a rule it is found that the output of the network 8 has produced across it a voltage for those pulse frequencies which form approximately a whole fraction of the frequency to which the network is tuned, that is to say if, starting with a passage of the thirtieth harmonic at a grid bias voltage of zero, the pulse frequency is /g X and so forth f the passage frequency.

The voltage occurring across the output of the filter is furthermore proportional to the pulse frequency.

Subsequently, the output voltage of the filter network is, if required, amplified with the use of a tube 9 and then rectified by a rectifying tube II].

The direct voltage occurring across the con? denser I I of the rectifying circuit is then used as control-grid voltage for the tube I. If the voltage across condenser I I is sufficiently high, which may be realised with the use of an amplifying circuit 9, an oscillator is obtained which is capable of producing a number of definite pulse frequencies.

If a voltage pulse is fed to one of the electrodes of the discharge tube I, the oscillator circuit jumps over to a different frequency.

Fig. 3 illustrates the relationship between the grid bias voltage Vg and the direct voltage V11 set up across the condenser I I, if the grid bias =3 voltage is abstracted from a separate battery and hence the voltage V11 does not yet serve as such voltage.

As a function of the voltage Vg, the maximum values of the output voltage V11 are found to be substantially located on a straight line A, whereas the minimum values extend just a little above the zero axis, as may be seen from the first three voltage peaks, shown in dotted lines.

It is furthermore found thatfor harmonics exceeding the thirtieth no stable adjustment is possible, since in this case thestraight line C which indicates the relationship between equal voltages Va and V11, has no intersection with the corresponding voltage variations.

Since, moreover, the voltage V11 is higher than is required for correct operation, it is advisable to apply a negative bias voltage to the anode of the diode H with the use of a battery I2. A suitable choice of this negative bias voltage and of the amplification due to the tube 9 ensures a voltage variation which is more satisfactorily matched to the'desired voltages and'which in Fig. 3 is denoted by the voltage peaks in full lines, the maximum voltage values being located substantially on a straight line B and the minimum values no longer extending beyond the zero ax1s.

The, line C intersects each voltage peak at two points, the right-hand intersection invariably indicating the voltage corresponding to the stable adjustment, since at the right-hand intersections the derivatives of the line C and the voltage peaks are of opposite polarity, so that, as is well-known, a divergence from the stable adjustment is immediately neutralized by an opposite tendency.

The pulses to be counted are fed to an electrode of the tube 5, for example, through connecting terminals l3, id to the control-grid.

Initially the pulse generator produced pulses of a definite frequency, resulting in a condenser voltage V11 corresponding therewith.

Each pulse to be counted causes a transition to a subsequent stable adjustment with the result that the voltage across the condenser is increased,

so that the voltage V11, after calibration of the circuit-arrangement, may be used for counting the pulses supplied.

If, for example the condenser H is connected in parallel with the series combination of a battery, a resistance and a discharge tube having a definite breakdown voltage, choosing the battery voltage to be such that the breakdown voltage of the tube after an increase in voltage of the condenser v11 corresponding with, say, 10 counted pulses, is attained, enables the condenser to be discharged.

After 10 pulses have been fed to the tube, the circuit-arrangement resumes its initial condition, that is to say without grid bias voltage, and is again ready for counting 10 pulses. After each 10 pulses the resistance in the discharge circuit of the condenser may have taken from it a pulse, which may be fed to an electrode of the tube of the subsequent counting circuit.

The circuit-arrangement shown in Fig. 2 provides a particularly suitable solution of the problem of discharging the condenser H. The condenser is connected in parallel with'the series combination of a resistance [5 and a gasfilled discharge tube ifi comprising a control-grid.

The control-grid of the tube id has fed to it a voltage which, if necessary subsequently to rectification (not shown), is taken from an oscillatory circuit [1.

The circuit H is included, through a transformer, in the output circuit of the tube l of the pulse generator. It is tuned to that pulse frequency of the pulse generator which occurs after a certain number of pulses to be counted, say 10, have been fed to the tube I.

As soon as 10 pulsesh'ave been counted, an alternating voltage occurs across circuit 11, with the result that the tube 16 becomes conductive and the resistance it has produced across it a voltage pulse, which may be fed to a subsequent counting circuit.

With the use of a battery I8 a suitable negative bias voltage may be fed to the control-grid of the tube It.

A circuit-arrangement of this kind for discharging the condenser H has the advantage that itis. substantially independent of voltage fluctuations and even in the case of replacement ofthe tube 55 by another does not entail diificult adjustment;

What I claim is:

l. A pulse counting device comprising a gen.- erator including anelectron discharge tube having a control electrode and an output circuit yielding impulses whose periodicity depends on the magnitude or" abias voltage on said control electrode, a periodicity control system including a filter network coupled to said output circuit and tuned to a harmonic of the fundamental periodicity of said impulses corresponding to a predetermined bias voltage on said control electrode thereby to develop a control voltage whose magnitude depends on the periodicity of said impulses, means to apply said control voltage to said control electrode to maintain the impulse periodicity of said generator at a value in accordance therewith, means to apply input pulses to be counted to said tube toweffect a transition in the periodicity of said impulses in accordance with the number of input pulses applied thereto, and means to derive an outputpulse from said control system when the periodicity of said impulses attains a predetermined rate.

2. A pulse counting device comprisingv a generator including an electron discharge tube having a control electrode and an, output circuit yielding impulses whose periodicity depends on the magnitude or" a bias voltage on said control electrode, a periodicity control system including a filter network coupled to said output circuit and tuned to a harmonic of the fundamental periodicity of said impulses corresponding to a predetermined bias voltage on said control electrode, a charging condenser and a rectifier coupling said condenser to the output of said filter network to establish across said condenser a control voltage whose magnitude depends on the periodicity of the impulses applied to said network,.means to impress said control voltage on said control electrode to maintain, the impulse periodicity of said generator at a value in accordance therewith, means to apply input pulses to be counted to said tube to effect a transition in the periodicity of said generator in accordance with the number of pulses applied thereto, and means to obtain an output pulsefrom said control system when the periodicity of said impulses attain a predetermined rate.

3. An arrangement, as set forth in claim 2, wherein said means to obtain an output pulse includes means to discharge said condenser when the periodicity of said generator attains a predetermined rate.

4. A pulse counting device comprising a gen--,

erator including an electron discharge tube having-a control electrode and an output circuit yielding impulses whose periodicity depends on the magnitude of a bias voltage on said control electrode, a periodicity control system including a filter network coupled to said output circuit and tuned to a harmonic of the fundamental periodicity of said impulses corresponding to a predetermined bias voltage on said control electrode, a changing condenser and a rectifier coupling said condenser to the output of said filter network to develop across said condenser a control vyoltagellwhose -magnitude depends on the pefio dicity of the impulses applied to said net- 5. An arrangement, as set forth in claim 4,

wherein said means to ignite said gaseous discharge tube includes a resonant circuit coupled to said output circuit and tuned to a frequency corresponding to said predetermined rate to produce an ignition voltage for said gaseous tube.

Number 6. A pulsecounting device comprising a blocking oscillator including an electron discharge tube having first and second control electrodes and an output circuit yielding impulses whose periodicity depends on the magnitude of bias voltage on said first control electrode, a control system including a filter network coupled to said output circuit and tuned to a harmonic of the fundamental periodicity of said impulses corresponding to a predetermined bias voltage on said first control electrode thereby to'develop a control voltage whose magnitude depends on the periodicity of said impulses, means to apply said control voltage to said first control electrode to maintain the periodicity of said oscillator at a value in accordance therewith, means to apply input pulses to be counted to said second control electrode to effect a transition in the periodicity of said oscillator in accordance with the number of pulses applied thereto; and means to obtain an output pulse from said control system when said periodicity attains a predetermined rate. PIETER JOHANNES KRAAYEVELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,115,877 Rocard May 3, 1938 2,470,303 Greenough May 17, 1949

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