US2570442A - Production of sharp pulses - Google Patents

Description

O Ct. 9, 1951 1 GROSDQFF 2,570,442

PRODUCTION 0F SHARP PULsEs Filed may 21. 194e `law-Zig ATTORNEY v Patented Oct. 9, 1.951 1;v

PRODUCTION OF SHARP PULSEs Igor Il.A Grosdoff, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 21, 1948, Serial No. 28,351

(Cl. 250V-'27) 6 Claims. i

My invention relates to the production of electrical pulses and particularly to vthe conversion of signals of varying slopes into pulses having a uniform slope.

An object of the invention is to provide an improved method of and means for producing electrical pulses that may be Varied through a wide repetition rate without any substantial change in their characteristics.

A further object of the present invention is to provide a simpliiied method and circuit for converting a sine wave signal into repetitive nonslnusoidal pulses. Y

A further object of the invention is to provide an improved method of and means for producing repetitive non-sinusoidal electrical pulses that may be varied in frequency.

A still further object of the invention is to provide an improved fast acting circuit for converting signals of varying slopes .into pulses of.

uniform slope.

In practicing one embodiment of theA present invention, a gas or vapor tube is employed which. is caused to break down once each cycle of an applied sine wave voltage and which is deionized quickly by application of. a reverse voltage. In one preferred embodiment of the invention, the

gas tube is connected between the anode ofa vacuum tube and ground, with an Output resistorv l embodiment of the invention,

Figure 2 is agroup of graphs that are referred to in explaining the operation of the circuit of Fig. 1, and f l Y Figure 3 is a circuit diagram of another embodiment of the invention.

Referring to Figure 1 of the drawing, there is shown a sine wave source I which may be varied in frequency by a control knob I I. The sine wave output signal I2 is applied to the input circuit of a vacuum tube I3. The tube I3 may be operated at zero bias as shown with its grid resistor I4 connected to ground, or a suitable negative bias may be applied to the grid I6. The anode I1 has a D.C. operating voltage applied to it from a +B source through an anode resistor I 8.

A gas or vapor tube I9 such as a neon or hydrogen-filled tube, for example, has one electrode 2I connected to the anode I1 and has the other electrode 22 connected through an output resistor R1 to ground.

A resistor R2 of suitable value is connected from a suitable positive voltage source such as -I-B to the junction point of electrode 22 and resistor R1 for maintaining said junction point at a suitable potential for rapidly deionizing the tube I9 as previously discussed.

Figure 2 illustrates the relation between the ap. plied sine wave signal I2 and the substantiallyy rectangular pulses 23 that appear across the output resistor R1. An important characteristic of the wave form of pulses 23 is that the front edge of the positive half cycle is always very steep and of unchanging Slope over a wide frequency range of the applied signal I2. The circuit has been Operated satisfactorily with the applied signal I2 varied from 20 cycles per second to 100,000 cycles per second and higher. It will be appreciated that with voltage of a given amplitude, the slope of a sine wave varies widely over such a frequency range. For this reason, conventional fast operating limiting circuits cannot give the same results@ as the present invention.

In order to obtain sharp pulses such as shown at 2B, the wave 23 is passed through a differentiating circuit comprising a small series capacitor 21 and a shunt resistor 28. By passing the signal 26 through a clipper or limiter, as is Well known in the art, the pulses of one polarity, such as the negative pulses, may be eliminated so that there is obtained one pulse for each cycle of the applied signal I2. These pulses of Wave 26 are of substantially the same amplitude and shape over the entire operating range of frequency of the apparatus.

The value of the deioniziing voltage or reverse potential applied across the gas tube I9 is not critical.

The particular resistance and voltage values.

employed will depend upon the particular tubes employed and upon the particular use to which the resistors R1, R2 and I8 may have values of the same Order,` for example.

'Ilheminvention is not limited to the particular The higher the reverse voltage, thev faster the tube I9 is deionized. However, the

embodiment shown in Figure 1. In Figure 3 there is shown another embodiment merely by way of example. Here the applied signal is obtained from a photoelectric cell circuit that may be utilized for counting objects carried on a conveyor belt, for instance. A photoelectric cell 3| is connected between ground and a point 32 on a voltage divider resistor 33, with a grid leak resistor 3d and a bias battery 36 between the cell 3| and ground.

A pentode 3l is shown in place of the triode I3 of Figure l. Voltage is applied to its anode 38 through an anode resistor 39. A gas tube 4l has an electrode l2 connected through a resistor 43 to the anode 39. The other electrode 44 of gas tube 4l is connected through a source of positive bias 43 to ground.

The signal appearing across the gas tube 4l each time it breaks down may be differentiated by a series capacitor 41 and a shunt resistor 48 and then clipped, if desired, for operating a count indicator or a control circuit.

It Will be noted that in Figure 3 the deionizing bias is provided by a battery i5 instead of -by the R1, Rz connection of Figure l. Similarly, in Figure l the resistor R2 can be omitted and a bias battery connected in the circuit from electrode 22 of the gas tube to ground. Also, in Figure 3 the output signals are reversed in polarity with respect to the output signals of Figure l.

From the discussion of the operation of `the circuit of Figure l, it will be appreciated that in the circuit of Figure 3 the output pulse will be substantially the same regardless of the slope of the signal or pulse applied fro-m the photoelectric cell circuit. For example, a slow moving object to be counted will gradually interrupt the beam of light directed toward the photoelectric cell so as to produce at the grid of tube 31 a signal of gradually changing slope whereas a fast moving object will produce a signal of comparatively steep slope. Both objects, however, will produce substantially the same kind of output pulse so that there will be an accurate count regardless of the speed of the objects being counted. Thus an object will be counted no matter how slowly it. is moving. Because of the deionizing feature of the circuit, the counting can be done at a very high speed.

In the claims the term gas tube is intended to include either gas or vapor tubes.

I claim as my invention:

1. A circuit for converting successively occurring variable slope signals into uniform slope pulses which comprises a gas tube, means for causing said tube to break down and conduct in one direction in response to the occurrence of each variable slope signal, bias means for reversing the polarity of the voltage across said tube after it breaks down and before the next variable slope signal occurs, said reverse polarity voltage having a value sufficient to deionize said tube quickly but not sufficient to make the tube break down and conduct in the opposite direction, and means for applying to an output circuit the pulse resulting from said tube conduction.

2. A circuit for converting successively occurring variable slope signals into uniform slope pulses which comprises a gas tube, means for causing said gas tube to break down and conduct in one direction in response to the occurrence of each variable slope signal, said means including a vacuum tube having an input circuit and an output circuit, said variable slope pulses being applied to said input circuit, and said gas tube being connected in said output circuit, bias means connected in series with said gas tube for reversing the polarity of the voltage across said gas tube after it breaks down and before the next variable slope signal occurs, said reverse polarity voltage having a value sufcient to deionize said gas tube quickly but not sufficient to make the gas tube break down and conduct in the opposite direction, and means for applying to an output circuit the pulse resulting from said gas tube conduction.

3. Acircuit for converting variable slope signals into uniform slope pulses which comprises a vacuum -tube having an anode and having an input circuit to which said variable slope signals are applied, an anode impedance through which a direct-current voltage is applied to said anode, a gas tube connected between said anode and groundso that it conducts when the voltage at said anode rises above a predetermined value, biasing means included in series with said gas tube with the polarity of the biasing voltage in the direction to oppose said conduction and having a value that exceeds the potential at said anode at a time following said gas tube conduction and preceding the next cycle or impulse of the variable slope signal, and means for applying vto an output circuit the pulse resulting from said gas tube conduction.

4. A circuit for converting successively occurring variable slope signals into` uniform slope pulses which comprises a vacuum tube having an anode and having an input circuit to which said Variable slope signals are applied, an anode impedance through which a direct-current voltagev is applied to said anode, a gas tube and an output resistor connected in the order named between said anode and ground so that said gas tube conducts when the voltage at said anode rises above a predetermined value, means for including a biasing voltage in series with said gas tube with the polarity of the biasing Voltage in the direction to oppose said conduction and having a value that exceeds the potential at said' anode at a time following said gas tube conduction and before the next cycle or impulse of the variable slope signal occurs, said biasing means including a resistor connected from a point at positive direct-current potential to the junction point of said gas tube and said output resistor, and means for applying to an output circuit the pulse resulting from said gas tube conduction and appearing across said output resistor.

5. In combination, a variable frequency source of sine wave signals, a circuit for converting said signals into pulses of uniform slope throughout the operating frequency range, saidV circuit comprising a gas tube, means for causing said gas tube to break down and conduct in one direction during the occurrence of the negative half cycle of said sine wave signal, bias means for reversing the polarity of the voltage across said gas tube during the next positive half cycle of said signal, said reverse polarity Voltage having a value sufficient to deionize said gas tube quickly but not sufficient to make the gas -tube break down and conduct in the opposite direction, and means for applying to an output circuit the pulse resultingfrom said gas tube conduction.

6. In combination, a variable frequency source of sine Wave signals, a circuit for converting said signals into pulses of uniform slope throughout the operating frequency range, said circuit com-lv prising a vacuum tube having an anode and having an input circuit to Which said sine Wave' 5 signals are applied, an anode impedance through which a direct-current voltage is applied to said anode, a gas tube connected between said anode and ground so that it conducts When the voltage at said anode'rises above a predetermined value during the negative half cycle of said sine Wave, biasing means included in series with saidy gas tube with the polarity of the biasing voltage in the direction to oppose said conduction and having a value that exceeds the potential at said anode at a time during the positive half cycle of said sine Wave, and means for applying to an output circuit the pulse resulting from said gas tube conduction.

IGOR E. GROSDOFF.

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

UNITED STATES PATENTS Hulst Oct. 14, 1947

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