JPS6224173A - Digital counting-rate meter - Google Patents

Abstract

PURPOSE:To enable digital counting with high reliability, by multiplying and adding a counting-rate obtained in the specified short sampling time and the previous average counting rate corresponding respectively to a weight-suffixed coefficient and by obtaining an average counting-rate by the weight average method. CONSTITUTION:An output of a counting-rate arithmetic operation circuit 14 is intro duced into the NO.1 weight-suffixied multiplication circuit 18 and the specified NO.1 weight-suffixed coefficient x is multiplied by a counting rate ri and r:x is issued from the circuit 18. And, the output of the circuit 18 has already been introduced into the one of the input sides of an addition circuit 20 and on the other input side, a value suffixed with a different weight is introduced into the average counting rate Ri-1 which was weight arranged at one measuring cycle beforehand. Namely, the output of the circuit 20 of the previous the time if introduced into a resistor 22 and counting rate Ri-1 is assumed as a signal lagged by one cycle by a controlling signal of a timing control circuit 16 and the signal is introduced into the NO.2 weight-suffixed circuit 24. Here, multiplication of the coefficient 1-x, representing subtration of the coefficient x of the circuit 18 from 1 is mode and the counting rate Ri-1 (1-x) is introduced into the circuit 20. Consequently, the average counting rate Ri fed out of the circuit 20 can be obtained by the specified equation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital count rate meter, and particularly to a digital count rate meter that is used for radiation monitoring and continuously measures the count rate of randomly input pulse trains.

[Prior Art] A count rate meter is used as a counting device in a radiotonic J4 radiation monitoring device, etc., and converts the radiation incident on the measuring device into an electrical pulse, calculates the count rate of this pulse train, and calculates the count rate. Measurements are made on the value of V).

Then, the number of pulses of the Ji number numerical value within a certain period of time is integrated to give an integrated average value per unit time, and this integrated average value is electrically processed so that it can be directly read with a meter of the device etc. Therefore, conventionally, a diode pump circuit that performs analog processing has been used, and the diode pump circuit converts a random input pulse train into an analog level, making it possible to easily read and stably measure the count rate.

That is, the diode pump circuit includes a parallel circuit of a capacitor 10 and a resistor 12, as shown in FIG.
supplied to Then, the parallel resistor 12 causes a discharge charge qI in the a direction shown in the figure, and a charge charge Q2 in the bh direction shown in the figure, which is 1q due to the input pulse (Q2 - manual pulse xq).
The 'c81 number rate is calculated, and the charging/discharging charge Q+,
When q2 moves, J: indicates the analog value of the voltage V between terminals A and B, which averages the number of input pulses.

Therefore, when the number of input pulses increases and the charge q2 supplied to the capacitor 10 becomes larger than the discharge charge q+, the voltage V between A and B increases, and conversely, the number of input pulses decreases and the voltage q2 becomes discharged. When the charge becomes smaller than q1, the voltage V decreases. In this way, since the voltage V between A and B is proportional to the change in the number of input pulses, this terminal A
By measuring the voltage between -B, it is possible to obtain the accurate h1 number rate of the input pulse train, and in the diode pump circuit, the counting rate is Count rate measurement can be performed with good responsiveness to changes.

[Problems to be Solved by the Invention] However, in the diode pump circuit, aging changes such as deterioration of capacitors and resistors that perform analog processing, or once these 1! Due to f-characteristics, etc., the amount of charge itself within the diode bomb circuit is unstable, resulting in measurement errors in the counting rate.

Therefore, in order to eliminate these drawbacks of analog circuits, we have developed a digital count rate meter, a device that calculates count values at predetermined time intervals and digitally calculates the average count per intermediate time to calculate the count rate. For example, if the count value per second is 6
A moving simple average type word count revision, etc., has been proposed, in which a count rate value (cps) of J3 per second is obtained by adding 0 and dividing by 60.

However, when trying to obtain measured values with a constant standard deviation in order to obtain reliable data using a device like this, it is necessary to First, such a simple average for each comparative time has the problem that the response to changes in the hI number band is poor compared to the weighted average circuit using the analog diode pump circuit described above. Simple average type digital counting rate for radiation counting equipment that needs to detect quickly! There was a problem that it was not appropriate to use .

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide a digital count rate meter that is digitally processed and has excellent responsiveness to changes in the count rate.

[Means and operations for solving the problem] In order to solve the problem, the present invention provides a counting rate calculation circuit that performs counting rate calculation at a predetermined short numbering period in response to changes in the counting rate; a first weighted multiplication circuit that multiplies the output of the count rate calculation circuit by a first weight coefficient of 1 or less; a memory that stores the previous average count rate; In a digital count rate meter that includes a second weight (=J multiplication circuit) that multiplies the second weighting coefficient obtained by subtracting the weighted coefficient, and an addition circuit that weights the outputs of both weighted multiplication circuits, It is characterized by calculating the current average counting rate from the weighted average of the counted rates.
The count rate of each measurement cycle obtained by the count rate circuit is weighted accordingly, and an average word count rate is determined by weighted averaging.

[Example 1 Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a digital count rate meter, which uses a 51 number band function to digitally count pulse trains corresponding to radiation doses.
In the circuit 14, a pulse is input every short limp time (Δt) controlled by the timing control circuit 16,
Four numerical values are obtained per unit time. That is, by dividing the integrated value NL (t indicates the measurement cycle number) accumulated over a certain period of time Δt by Δt, the counting rate Ti (Ctth) of one measurement cycle is calculated.

A characteristic feature of the present invention is that in a count rate meter that performs digital counting, in order to ensure responsiveness to changes in the counting rate of a diode pump circuit that performs analog counting,
The counting rate obtained by the counting rate calculating circuit 14 for each measurement cycle is weighted and averaged to obtain a stable counting rate value at the present time. For this reason, the above t1
The output of the number band circuit 14 is input to a first weighted multiplication circuit 18, and a predetermined first weighting coefficient χ within the range of θ to 1 corresponding to the unit of the output is The first weighted multiplication circuit 18 outputs a γ element χ. The output of the first weighted multiplication circuit 18 is inputted to one input side of the addition circuit 20, and the other input side is inputted to the weighted average count rate R1 of the previous measurement cycle.
A value in which −1 is given a different weight is input. That is, the output of the narrow end circuit 20 of the turn is input to the register 22, and based on the control signal of the timing control circuit 16, the count rate R is input to the weighted multiplication circuit 24. Here, a second handing coefficient (1-χ) obtained by subtracting the first weighting coefficient χ of the first weight synergistic fraud circuit 18 from 1 is multiplied, and Rl-
t (1-χ) will be input to the adder circuit 20.

Therefore, the average count rate Ri output from the adder circuit 20 is determined by the following equation.

Ri ”Ri-t (1-χ)+1 element χ...(1
) That is, the average nI number band R for each measurement 1 nicle,
=R8 (1-χ) +γ1 χ R2=Ro (1-χ)2 +γ! χ(1−χ)+γ
2χR3=no(1-χ)3 ←γ1 χ(1-χ)2
1γ2 χ(1-χ) +γj χRL =Ito
(1-χ) Upper +γ 1 χ (1-χ)1
-1÷γ2χ(1-χ) ...+γLχ For the 6th output 1 element of the 81 number rate calculation circuit 14 in the i (7=0.1, 2...)th measurement, The first weighting coefficient χ, which is always constant, is multiplied, and the second weighting coefficient (1-χ) is multiplied every measurement cycle for the previous output R1-1, R knee 2, etc. ,
If it has been measured before, it is somewhat flat this time.

The degree of contribution to the output of the adder circuit 20, which is the uniform counting band, gradually decreases.

Comparing the count rate Ri obtained in this way with the diode pump circuit described above, we find that the first term R1-
1(1-χ) corresponds to the accumulated charge remaining after subtracting the charge q1 discharged through the resistor 12 from the capacitor 0 in FIG. 4, and the second term γLχ corresponds to the accumulated charge newly accumulated in the capacitor 0. This corresponds to the charged charge q2. Therefore, in the present invention, equation (1) can be analyzed to the same degree as the diode pump circuit described above, and the weighted average time constant τ corresponds to the time constant of the diode pump.
This time constant τ and the second weighting coefficient (1-χ) in the present invention have the following relationship.

Fake (1-χ)=cxp(--)...(2)
τ In other words, χ is the attenuation coefficient when the time constant τ is attenuated by Δ(, and the time constant τ is given by the following equation.

Δ[τ= −□ (3) Qn (1−χ)−1 Therefore, the present invention can perform measurement using the same weighted average characteristic as that of a diode pump circuit.

Digital measurement of radiation m is performed with the above configuration, and the results actually measured using the apparatus of the present invention will be described next.

The measured count value is the IT value measured every second, and is the data shown in FIG. It has an average count rate (cps) and standard deviation as shown in the table below.

(Table) The results of digital counting based on this data are shown in Figure 3, where the broken line 10o indicates the count value per second of 60
The solid line 200 is obtained by simple moving average (digital moving average type), and the solid line 200 indicates the time constant of the diode pump circuit
With the time constant of the present invention so that it is equivalent to the case of 0 seconds =
It was obtained by setting Δ[ and χ directly (directly) assuming 30 seconds.As is clear from this figure, the rise of the device of the present invention is faster than that of the digital moving simple average type between time a and b. is faster, and the device of the present invention shows higher counting confidence at time C. This shows that it has better responsiveness to changes in the counting rate.

Furthermore, between time c and d, the moving simple average type has 51Cp
The counting rate drops sharply from s to 50 cps, but in the device of the present invention, it drops slowly, which indicates good responsiveness to the directionality of the M dispersion pattern change.

[Effects of the Invention] As explained above, according to the present invention, a predetermined short limp ring opening/time has a range corresponding to each of the 1 (1 worked) number band and the previous average 51 number rate. I used a thin frame with the addition coefficient as the east exit, and the average word rate was calculated using a weighted average.
By digital counting processing, it is possible to continuously measure a randomly input pulse train with a good response state equivalent to that obtained when processing with a diode pump to changes in the number band.

Furthermore, by making reliable digital counting possible, it is possible to eliminate measurement errors caused by aging, temperature characteristics, etc., which were problems with analog circuits.

4. Brief description of the drawings Fig. 1 is a block diagram showing a preferred embodiment of the digital counting rate = 1 according to the present invention, Fig. 2 is a graph showing the counting rate per second, and Fig. 3 is a block diagram showing a preferred embodiment of the present invention. A graph diagram showing the count rate measured by a digital count rate meter. FIG. 4 is a circuit diagram showing a part of the diode pump circuit.

14...Reduced band abstraction circuit 18... First weight synergistic n circuit 20...Addition circuit 24... Second weighted multiplication circuit.

Claims (1)

[Claims] (1) In a digital count rate meter that continuously digitally measures the number of input pulses per unit time, a count rate calculation circuit having a predetermined short sampling period and a first weighting coefficient are applied to the output of the count rate calculation circuit. a first weighted multiplication circuit that multiplies the previous average count rate, a memory that stores the previous average count rate, a second weighted multiplication circuit that multiplies the previous average count rate by a second weighting coefficient, and both weighted multiplication circuits. 1. A digital count rate meter, characterized in that the digital count rate meter includes an addition circuit that adds the outputs of the count rate meter, and calculates the average count rate by weighted averaging to perform measurement with good responsiveness to changes in the count rate.