JPH02155311A - Random pulse counter - Google Patents

Abstract

PURPOSE:To correct missing of count by discriminating a random pulse signal and counting a time while the random pulse signal per unit time is inputted and a time while no random pulse signal is inputted. CONSTITUTION:A threshold detector 23 outputs a detection signal 27 while a peak of a random pulse signal 21 exceeds a threshold level. A clock pulse signal 33 is masked by the detection signal 27 in a gate circuit 28 and by an output signal 30 in a gate circuit 31, a pulse signal 34 outputted from the gate circuit 28 is counted by a count decrement device 35 and a pulse signal 31 outputted from a gate circuit 39 is counted by a count decrement device 42. The pulse number of the random pulse signal 21 interleaved by a peak discriminator 22 is corrected by adding a pulse signal 44 outputted from a gate circuit 25 to the pules number.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a random pulse counting device for counting random pulse signals, and particularly to a device for correcting miscounting of random pulses.

"Prior Art" This type of device is used, for example, in a radiation measurement device.

We will briefly explain the general configuration of radiation measurement equipment. Fourth
As shown in the figure, first, a radiation detector 1 detects radiation and outputs a pulse signal 2. This pulse signal 2 is amplified by an amplifier 3. The pulse signal 4 outputted from the amplifier 3 is discriminated by a pulse height discriminator 5 and converted into a pulse signal 6 having a small width. This pulse signal 6 is counted by a counter 7.

This radiation measurement device records one event (detection of radiation in this case) as one independent pulse with a finite width, so after recording one event, it records the next event. There is a minimum amount of time (dead time) required for recording. This time may be determined on the side of the radiation detector 1 or on the side of the attached circuit 3.5.7.

Next is an example of counting down. As shown in FIG. 5, the intervals of events 8 entering the radiation detector 1 are random (FIG. 5A). If the interval between the two events 8A and 8B is small, the pulse signals 4A and 4B indicating the respective events 8A and 8B will overlap (FIG. 5B). For this reason, the pulse signal 4B is dropped in the pulse height discriminator 5, causing a miscount in the counter 7 (FIG. 5C).

A conventional technique for correcting such miscounting is described in Japanese Patent Publication No. 56-37512. This technique is based on the following generally known counting loss correction formula.

n-・・・・・・(1) -mr n: true counting rate m: Measured counting rate T: Dead time That is, when this formula (1) is expanded, it becomes the following formula.

n=m+m (mr) +m (mr)2 +・・・
...+m (mr)0 + ...... ...... (2) Rewriting the correction terms of each method in this equation (2) results in the following equation.

0th order: mo = m 1st order: m+ = m (rnτ) = mo (moτ) 2nd order: m2 = m (mr) 2 = m, (mo τ) Nth order: mx = 171 (mr) N = 17' l, -, (ma
r)... (3) In the conventional technology, based on this equation (3), N
By repeating the following correction, the missing count was corrected.

"Problem to be Solved by the Invention" However, in the conventional technology described in O1, since equation (1) is a correction equation for the paralysable model,
There is a problem in that it is not suitable for the case of the model le).

Also, since the N-th correction is repeated, the calculation circuit is
It is necessary to provide stages, and when the circuit scale becomes large,
There are also some problems.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to improve a technique for correcting missing counts when counting random pulse signals. In other words, it is an object of the present invention to provide a random pulse counting device that can correct both paralytic and non-paralytic models, requires a small circuit configuration, and can perform correction in real time.

"Means for Solving the Problem" The means taken by the present invention to achieve the above-mentioned object are as follows:
This will be explained using drawings.

As shown in FIG. 1, the random pulse counting device according to the present invention includes the following means.

(1) Discrimination means lO0 for discriminating the random pulse signal 9
Here, the term "random pulse" refers to a pulse in which at least one of pulse width and pulse interval is irregular.

(2) While the random pulse signal 9 is being input, the first
The first detection means 13° which outputs the detection signal 12 of (3) the second detection means 15° which outputs the second detection signal 14 while the random pulse signal 9 is not input (4) per unit time The first detection signal output time ΔT,
First timer means 16 for measuring the first detection signal output time ΔTa/ΔT1 Here, "measuring the first detection signal output time ΔTa/ΔT1 per unit time" means the first detection signal output time ΔTa/ΔT per unit time. It includes an embodiment in which ΔTd/ΔTt is indirectly detected by detecting the reciprocal value ΔT, /ΔT of .

(5) Second detection signal output time per unit time ΔTL/
The second timer 17 measures the second detection signal output time ΔT, /ΔTL per unit time, as in the first timer 16. The reciprocal value ΔTL/ΔT of the second detection signal output time ΔT, /ΔTL.

This includes an embodiment in which ΔT, /ΔTL is indirectly detected by detecting .

(6) Second detection signal output time per unit time ΔTt/
The ratio ΔTd/ΔT of the first detection signal output time ΔTa/ΔT per unit time to ΔTL.

Gate means 18° for passing the output pulse signal 11 of the discrimination means 10 when the number J of the discrimination means 10 is reached.
and counting means 20° for adding and counting the number of pulses (△Td/△T,)·m of the output pulse signal 19 of the gate means 18. ``Operation'' In general, the relationship between the true number of pulses n of the random pulse signal and the count value m is expressed by the following equation, regardless of the paralytic or non-paralytic model:

m　　　　　　　l’, T: Real time TI Ni Live Time When this equation (4) is transformed, it becomes the following equation.

Td: dead time (Td=T, -t) The present invention corrects for missing counts based on this equation (5).

The random pulse counting device according to the present invention first discriminates the random pulse signal 9 by the discrimination means 10.

Further, this random pulse signal 9 is transmitted to the first detection means 13.
and is also input to the second detection means 15. and the first
The detection means 13 outputs the first detection signal 12 while the random pulse signal 9 is being input. On the other hand, the second detection means 15 outputs the second detection signal 14 while the random pulse signal 9 is not input.

The first timer 16 calculates the first detection signal output time ΔTa/ΔT based on the first detection signal 12.
Time L. On the other hand, the second timer 17 measures the second detection signal output time ΔT, /ΔTL per unit time based on the second detection signal 14.

Based on the timing results of the first clocking means 16 and the second clocking means 17, the gate means 18 calculates the first time per unit time for the second detection signal output time ΔT, /ΔTt, which has a waiting time of about tg. Detection signal output time ΔTa/ΔTL
The output pulse signal 11 of the discrimination means 10 is passed at a ratio of ΔTd/ΔT. As a result, the number of pulses m' of the output pulse signal 19 of the gate means 18
is expressed by the following formula.

m: number of pulses of the random pulse signal 9; and the counting means 20 adds and counts the number m of pulses of the output pulse signal 11 of the discriminating means IO and the number m' of pulses of the output pulse signal 19 of the gate means 18; That is,
The counting result M of the counting means 20 is as shown in the following equation.

As is clear from a comparison of Equation (5) and Equation (7), the above-mentioned action allows the correction of counting omissions based on Equation (5) to be performed.

"Example" Hereinafter, an example of the present invention will be described in detail using the drawings.

This example shows an example of application to a radiation measuring device. First, the structure of the radiation measuring device according to this embodiment will be explained.

The random pulse signal 21 shown in FIG. 2 is obtained by detecting radiation with a radiation detector (not shown) and amplifying the detected signal with an amplifier (not shown).

This random pulse signal 21 is a pulse signal with irregular pulse width, pulse interval, and wave height.

This random pulse signal 21 is input to a pulse height discriminator 22 and a threshold detector 23. The pulse height discriminator 22 discriminates the random pulse signal 21 based on the pulse height. The pulse signal 24 output from the pulse height discriminator 22 is input to a gate circuit 25 and an adder 26.

The threshold detector 23 outputs a detection signal 27 when the wave height of the random pulse signal 21 exceeds a threshold value. This detection signal 27 is input to a gate circuit 28 and a NOT (negation) circuit 29.

The NOT circuit 29 outputs an inverted signal of the detection signal 27. An output signal 30 of this NOT circuit 29 is input to a gate circuit 31.

The oscillator 32 outputs a clock pulse signal 33. This tarok pulse signal 33 is input to gate circuits 28 and 31.

The gate circuit 28 transmits the clock pulse signal 33 while the detection signal 27 is input. A pulse signal 34 outputted from this gate circuit 28 is inputted to a counter-reducer 35 .

The counter 35 is for decreasing the pulse signal 34 at a decreasing rate N. The pulse signal 36 output from the counter 35 is input to the set input terminal of the flip-flop circuit 37.

The gate circuit 31 transmits the clock pulse signal 33 while the output signal 30 of the NOT circuit 29 is input. A pulse signal 38 output from this gate circuit 31 is input to a gate circuit 39.

The gate circuit 39 transmits the pulse signal 38 while the output signal 40 of the flip-flop circuit 37 is input. Pulse signal 41 outputted by this gate circuit 39
is input to the counter 42.

The counter-down device 42 steps down the pulse signal 41 at the same step-down rate N as the counter down-down device 35. This counter 4
The pulse signal 43 outputted by the flip-flop circuit 37 is input to the reset input terminal of the flip-flop circuit 37.

The flip-flop circuit 37 starts outputting when the pulse signal 36 output from the counter 35 is input, and stops outputting when the pulse signal 43 output from the counter 42 is input.

Output signal 40 of flip-flop circuit 37 is input to gate circuits 25 and 39.

The gate circuit 25 transmits the pulse signal 24 output from the pulse height discriminator 22 while the output signal 40 of the flip-flop circuit 37 is input.

A pulse signal 44 output from this gate circuit 25 is input to a delay circuit 45.

The delay circuit 45 delays the pulse signal 44 output by the gate circuit 25 for a required period of time.

A pulse signal 46 output from this delay circuit 45 is input to an adder 26.

The adder 26 receives the pulse signal 2 output from the pulse height discriminator 22.
4 and the pulse signal 46 output from the delay circuit 45. A pulse signal 47 output from this adder 26 is input to a counter 48.

The counter 48 counts this pulse signal 47.

Next, the operation of the apparatus of this embodiment will be explained.

When the wave height of the random pulse signal 210 exceeds a threshold value (the level is indicated by the dashed line in FIG. B) is output. At this time, random pulse signals that overlap with the previous pulse signal, such as the random pulse signal 21A, and those whose wave height has not reached the threshold value, such as the random pulse signal 21B, are dropped. That is, random pulse signals 21A and 21
The pulse signal 24 corresponding to B is not output.

The threshold detector 23 outputs a detection signal 27 (FIG. 3C) while the wave height of the random pulse signal 21 exceeds a threshold value (indicated by a two-dot chain line in FIG. 3A). This detection signal 27 indicates the time during which the random pulse signal 21 is input, that is, the dead time T. Furthermore, the NOT circuit 29 inverts the detection signal 27 and outputs an output signal 30 (FIG. 3D). This output signal 30 indicates the time during which the random pulse signal 21 is not input, that is, the live time T.

A clock pulse signal 33 (FIG. 3E) generated by the oscillator 32 is masked by the detection signal 27 in the gate circuit 28. Further, the clock pulse signal 33 is masked by the output signal 30 in the gate circuit 31 . The pulse signal 34 (FIG. 3F) output by the gate circuit 28 is counted by a counter 35. The counter 35 is
When the number of pulses reaches N, the pulse signal 36 (Fig. 3 H)
Output.

Let us now consider the case where the counter 35 outputs the pulse signal 36A. The following explanation will be made with this point as the starting point.

The counter 35 counts the pulse signals 34 again,
When the number of pulses reaches N, a pulse signal 36B is output. This time t1 is expressed as follows.

t 1 Convex IL N: Decrease rate tc: clock pulse period ΔT, /ΔT,: Dead time rate in time interval 1+ When formula (8) is transformed, it becomes the following formula.

Further, by inputting the pulse signal 36A to the set input terminal of the flip-flop circuit 37, the output signal 40 of the flip-flop circuit 37 (the third diagram is H (high)
become the level. As a result, the gate circuit 39 becomes open, and the pulse signal 38 (the third
Figure G) is transmitted. The pulse signal 41 (FIG. 3J) outputted from this gate circuit 39 is counted by a counter 42. When the number of pulses reaches N, the counter 42 outputs a pulse signal 43A (K in FIG. 3). The time t2 at which the pulse signal 43A is output at this time is expressed as follows.

ΔT, /ΔTL ; Live time rate formula (10) in time interval t1 is transformed into the following formula.

By inputting the pulse signal 43A to the reset input terminal of the flip-flop circuit 37, the output signal 40 of the flip-flop circuit 37 becomes L (low) level. The gate circuit 25 is open while the output signal 40 is at H level. In other words, the gate circuit 25 operates in the time interval t2.
The pulse signal 24 will be sent out only in this case.

Therefore, the number m' of pulses of the pulse signal 44 (L in FIG. 3) output by the gate circuit 25 is as follows.

m'= ・m ・・・・・・(12) m:
Equation (6) is obtained by transforming Equation (12) based on the pulse equations (9) and (11) of the pulse signal 24 in time interval t1.

The pulse signal 44 output by the gate circuit 25 is delayed by the delay circuit 45 so as to have a different timing from the pulse signal 24 output by the pulse height discriminator 22. and,
The pulse signal 24 output from the pulse height discriminator 22 and the pulse signal 46 (M in FIG. 3) output from the delay circuit 45 are added by an adder 26.

The number M of pulses of the pulse signal 47 output by the adder 26 is expressed by equation (7). That is, the number of pulses (n
-m) is corrected by adding m'.

The number M of pulses of this pulse signal 47 is counted by a counter 48. This counting result is output to an external device (not shown) as a radiation measurement value.

Although one embodiment of the present invention has been described above using an example of application to a radiation measuring device, the present invention is not limited to application to a radiation measuring device, but can be applied to general training for correcting miscounting of random pulses. .

"Effects of the Invention" As explained above, according to the present invention, the first time measuring means measures the first detection signal output time per unit time, and the second time measuring means measures the first detection signal output time per unit time. The second detection signal output time is measured. Then, by the gate means, at the ratio of the first detection signal output time per unit time to the second detection signal output time per unit time,
The output pulse signal of the discrimination means is passed through. By adding and counting the pulse signal obtained in this way with the output pulse signal of the discrimination means by the counting means, the equation (7
).

Therefore, according to the present invention, the following effects are achieved.

(1) Since complicated calculations (for example, N-stage approximation calculations based on equation (3)) are not performed as in the conventional method, the circuit size can be reduced, and reliability and economical efficiency are improved.

(2) Appropriate corrections can be made regardless of whether it is a paralytic model or a non-paralytic model. Furthermore, it can be applied to general counting of pulses with irregular pulse widths or pulse intervals.

(3) Since the output pulse signal of the discrimination means is masked by the gate means and the pulse signal obtained thereby is added to the output pulse signal and counted, correction can be performed in real time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of a radiation measuring device according to an embodiment of the present invention, and FIGS. FIG. 4 is a block diagram showing the configuration of a general radiation measurement apparatus, and FIGS. 5(A) to 5C) are waveform diagrams showing signals at each part in FIG. 4. 9...Random pulse signal, 10...
Discrimination means, 11... Output pulse signal, 12... First detection signal, 13... First detection means, 14... Second Detection signal, 15...Second detection means, 16...First clocking means, 17...Second timing means, 18...Gate Means, 19...Output pulse signal, 20...
...Counting means. Applicant: Japan Atomic Energy Company, Ltd.

Claims (1)

[Scope of Claims] Discrimination means for discriminating random pulse signals; first detection means for outputting a first detection signal while the random pulse signal is being input; and while the random pulse signal is not being input. , a second detection means for outputting a second detection signal, and a second detection means for outputting a second detection signal;
a first timer for measuring the output time of the second detection signal per unit time; and a second timer for measuring the output time of the second detection signal per unit time.
a gate means for passing the output pulse signal of the discriminator at a ratio of the second detection signal output time per unit time to the first detection signal output time per unit time; 1. A random pulse counting device comprising: counting means for adding and counting the number of pulses of the output pulse signal of the means and the number of pulses of the output pulse signal of the gate means.