JPH10239440A - Digital counting rate meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a noise to prevent the wrong counting, and measure a counting rate. SOLUTION: A present count value 21 is compared with a previous count value 21 in a judging block 32, and when the present count value is within an allowable range, the present count value 21 is used and inputted to an integrating block 22 to determine a counting rate (n). When the present count value exceeds the allowable range upper limit as the result of the above comparison, the previous count value is outputted instead of the present count value. Further, the state exceeding the allowable range upper limit is continued for a prescribed period, the counting rate is determined by use of the previous count value instead of the present count value within this period. Further, when the state exceeding the allowable range upper limit is continued after the lapse of the prescribed period, the counting rate is determined by use of the present count value. When the present count value is returned into an allowable range from the state exceeding the allowable range upper limit, the processing is returned to the initial processing based on the comparison result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital counting rate meter used for, for example, a radiation monitoring device.

[0002]

2. Description of the Related Art Conventionally, as a digital counting rate meter of this type, there has been an apparatus disclosed in Japanese Patent Publication No. Hei 3-20717, for example. In FIG. 14, 1 is a counter, 2 is a calculator, and 3 is an output count rate.

FIG. 15 is a block diagram showing a flow of arithmetic processing in the arithmetic unit 2 shown in FIG. Reference numeral 21 denotes a current count value indicating the count result counted by the counter 1 and input to the arithmetic unit 2, and reference numeral 22 denotes an integration for calculating a difference between the current count value 21 and the negative feedback count value and algebraically integrating the difference. Block 23 is a count rate calculation block that calculates and outputs the current count rate using the integrated value as the output of the integration block 22, and 24 is a product of the previous count rate and the sampling time to obtain a negative feedback count as a negative feedback count. A negative feedback block 25 for performing a negative feedback to the counter 25 is a control block for resetting the counter 1 and executing the arithmetic operation of the arithmetic unit 2 at regular intervals.

Next, the operation will be described. The counter 1 counts the number of pulses to be measured at every fixed sampling time (ΔT), and as a result of the current measurement, the current count value 21
(ΔN _IN ) is output. The integration block 22 receives the current count value 21 (ΔN _IN ) and negative feedback the product (n ′ × ΔT) of the previous count rate (n ′) and the sampling time (ΔT) calculated in the negative feedback block 24. Input as the count value (ΔN _B )
The difference (.DELTA.N _IN of (.DELTA.N _IN) and a negative feedback count (.DELTA.N _B)
−ΔN _B ), and adds the difference to the previous integrated value (M ′) to output the current integrated value (M).

The count rate calculation block 23 receives the current integrated value (M), and calculates and outputs the current count rate (n) so that, for example, the standard deviation is constant. Negative feedback block 2
4 inputs the output of the counting rate calculation block 23 and inputs the output to the accumulation block 23. Accordingly, blocks 22, 23 and 24 constitute a closed loop, it is satisfied ΔN _IN = ΔN _B in equilibrium point of the closed loop. The control block 25 controls the reset of the counter 1 and the arithmetic processing of the arithmetic unit 2 so as to be executed at regular intervals. It is known that the standard deviation σ of the count rate when radiation is measured using the above digital count rate meter is expressed by the following equation (1). σ = (1 / 2nτ) ^1/2 --- (1) where n: counting rate, τ: time constant

A closed loop feedback gain G
Is expressed as in the following equation (2). _{G = 1 / τ = dF B} (M) / dM ----- (2) However, to be F _B (M) = n standard deviation σ becomes constant, is necessary to make constant the nτ Yes, F _B (M) can be realized by using the following equations (3) and (4). 1 / nτ = [1 / F B (M)] · [dF B (M) / dM)] = r = constant ----- (3) Thus, _{[dF B (M) / dM)} ] = r F _B (M) −−− (4) A function that becomes a constant multiple by differentiating is represented by an exponential function as in equation (5).

Therefore, F _B (M) = η · ^erM = η · 2 ^{rM / ln2} (5) where η is a constant. In the above equation, η = 1, r = 2− ^X · ln2 Then
The standard deviation σ and the count rate n are represented by the following equations (6) and (7).

[0008] ^{σ = (1 / 2nτ) 1/2} = (r / 2) 1/2 = (2 -X-1 · ln2) 1/2 ------ (6) n = F B (M ) = E ^rM = 2 ^{rM / ln2} (7) where r = 2 ^−x · ln2

[0009]

The conventional digital counting rate meter is constructed as described above. For example, since the time constant is inversely proportional to the counting rate, the time required for the counting rate to return to the normal value when noise enters is measured. Measurement may interfere with the measurement. In particular, when the normal background level is a low count rate and the standard deviation is small, it may take several tens of minutes to recover. Further, there is a drawback that the detection is delayed when trying to detect a device abnormality in which the measured pulse is lost or reduced due to a detector failure or the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can prevent erroneous counting due to transient noise pulses, and can respond quickly to a sudden decrease in the number of pulses to be measured. The purpose is to obtain a counting rate meter.

[0011]

[Means for Solving the Problems]

(1) A digital count rate meter according to the present invention has a counter for counting the number of pulses to be measured for each sampling period, and the count rate meter derives a count rate based on the count value of the counter. Comparing means for comparing the current count value with the previous count value to determine whether or not the current count value is within an allowable range. If the current count value is within the allowable range based on the comparison result, the current count value In the state where the current count value exceeds the upper limit of the allowable range in the comparison result, the previous count value at the time when the count value exceeds the upper limit is fixed, and the previous count value of the comparing means is set to the fixed last time. The count value is compared with the current count value, and the count rate is calculated using the fixed previous count value within a predetermined period, and the count rate is calculated. After this time, the counting rate is calculated with the current count value, and when the current count value falls within the allowable range from the state where the current count value has exceeded the upper limit of the allowable range, the comparing means uses the fixed count value. It is provided with an operation means for returning to the comparison processing that does not exist.

(2) A counter for counting the number of pulses to be measured for each sampling period, and a count rate meter for deriving a count rate based on the count value of the counter. The comparing means for comparing with the previous count value to determine whether or not the current count value is within the allowable range, and the calculating means, based on the present count value, if the current count value is within the allowable range in the comparison result. In the state where the current count value exceeds the upper limit of the allowable range in the comparison result, the previous count value at the time when the count value exceeds the upper limit is fixed, and the previous count value of the comparing means is the fixed previous count value. The value is used to compare the current count value with the current count value, and the count rate is determined using the fixed previous count value as a limit for a predetermined period, and further, the count rate is calculated for the predetermined period. If the state continues to exceed the upper limit of the allowable range later, the count rate is calculated with the current count value for a certain period, and after the certain period elapses or the state in which the current count value exceeds the upper limit of the allowable range, the current count value becomes the allowable value. When the state is within the range, there is provided a calculating means for returning to the comparing processing not using the fixed count value by the comparing means.

(3) In the above (1) or (2), the counting rate meter has a counter for counting the number of pulses to be measured in each sampling period, and the last negative feedback from the current count value of this counter is provided. A difference is obtained by subtracting the count value (the product of the previous count rate and the time of one sampling cycle), a difference is algebraically integrated, and a count rate meter that derives a count rate based on the integrated value is used. In this case, the previous negative feedback count value is used instead of the previous count value.

(4) A counter for counting the number of pulses to be measured for each sampling period, and a count rate meter for deriving a count rate based on the count value of the counter, the count value of the current time is set to a lower limit of an allowable range. A time constant changing means for increasing the time constant for calculating the count rate when the predetermined period is reached is provided below.

(5) The digital count rate meter according to any one of the above (1) to (3) is provided with time constant changing means for the digital count rate meter according to the fourth aspect.

(6) In any one of the above (1) to (5), there is provided an alarm means for sending out an alarm signal when the current count value becomes equal to or less than the lower limit of the allowable range and continues for a predetermined period. It is.

(7) In any one of the above (1) to (6), the allowable range is a value based on the standard deviation of the counting rate.

(8) In any one of the above-mentioned items (1) to (7), when a test is performed, the current count value is input directly to the arithmetic means by bypassing the comparing means.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The basic configuration is the same as that of the prior art shown in FIG. 14. FIG. 1 is a block diagram showing the flow of the arithmetic processing in the arithmetic unit 2 in FIG. 14, and 31 to 33 relate to the present invention. Blocks 21 to 25 are the same as those in the conventional example.

Reference numeral 31 denotes a previous count value which is counted and stored by the counter 1 in the previous fixed period, and 32 denotes the present count value 21 which is inputted and compared with the previous count value 31 to judge whether or not it is within an allowable range. A block 33 is a noise removing block for removing noise. FIG. 2 is a flowchart showing the procedure of the arithmetic processing.

Next, the operation will be described. (1) The previous count value 31 (ΔN ′ _IN ) is counted and stored by the counter 1 in the previous fixed cycle, and is updated every fixed cycle after calculating the count rate. (2) The determination block 32 determines that the current count value 21 (ΔN
_IN ) and the previous count value 31 (ΔN ′ _IN ) are input and compared to determine whether the count value is within the allowable range and output the determination result to the noise removal block 33.

(3) The noise removal block 33 calculates the current count value 21 (ΔN _IN ) and the previous count value 31 (ΔN ′).
_IN ) and the judgment result of the judgment block 32. If the judgment result is within the allowable range, the current count value 21 (ΔN
_IN ) is output to the integrating block 22. (4) On the other hand, if the upper limit of the allowable range is exceeded, the updating of the previous count value 31 (ΔN ′ _IN ) is stopped and the previous count value 31 (ΔN ′ _IN ) is output to the integrating block 22.

(5) Further, when the previous count value update stop is continued (when the present count value is compared with the previous count value and the state exceeding the upper limit of the allowable range is continued), the fixed cycle including the cycle is performed. The output to the integrating block 22 for a predetermined period of time that is a multiple of a multiple of
(ΔN ' _IN )

(6) After the above-described predetermined period, the output to the integrating block 22 is returned from the previous count value (ΔN ′ _IN ) to the current count value 21 (ΔN _IN ), and the stop of the previous count value update is released. Until the current count value falls within the allowable range (until the current count value falls within the allowable range).
_IN ) and output

(7) When the current count value returns to within the allowable range, the stop of updating the previous count value is released, and the process returns to (2) above, which is a normal processing operation. Through this series of processes, the transient noise is detected by the decision block 32 and removed by the noise removal block 33.

The upper limit of the allowable range of the decision block 32 is set, for example, as follows. Upper limit of allowable range: 3 x (previous count value) ^1/2 + (previous count value) ------ (8) However, if the previous count value is 0, it is regarded as 1.

The above operation will be described in detail with reference to the flowchart of FIG. 2 and the flowcharts of FIGS. 3, 4, and 5 showing the output processing of the count value and the determination block. (1) The previous count value is initialized (set to ∞), the last count value update stop time is initialized (set to 0), and the device is reset (S1). (2) The current count value (ΔN _IN ) and the previous count value (ΔN ′ _IN ) are read (S2, S3),

(3) (ΔN _IN > k × ΔN ′ _IN ) where k is a constant and the two are compared.
4), (4) Since the previous count value update stop time remains initialized, it becomes "0" (S7), (5) The current count is output (S10), and the process returns to S2. Normally, measurement is performed by repeating the above steps S2, S3, S4, S7, and S10. (A, b,... In FIG. 3)
・ E state)

Next, the case where the current count value exceeds the upper limit of the allowable range in step S4 will be described. (6) In step S4 (comparison between e and f in FIG. 3), if the current count value (f in FIG. 3) exceeds the upper limit of the allowable range, the previous count value update time is 0 (S5). 7)
The updating of the previous count value is stopped (S9). (The previous count value e in FIG. 3 is not updated, and the previous count value is fixed at e.) (8) The previous count value is output (S11). (Output e in FIG. 3)

Next, a case where the noise is eliminated once will be described. (9) As the continuation operation from (8) above, the current count value (g in FIG. 3) and the previous count value (e in FIG. 3) are read (S2, S3), and the two are compared to eliminate noise. If the current count value is within the allowable range (S
4), (10) Since the previous count value update stop time is not "0" (S7), (11) The update of the previous count value (e in FIG. 3) is released, and the previous count value update stop time is reset. (S
8). (12) Output the current count value (g in FIG. 3) (S1)
0).

As shown in FIG. 4, when the noise occurs over two periods of the sampling period, (13) as the continuous operation from the above (8), the current count value (g in FIG. 4) and the previous count The value (e in FIG. 4) is read (S2, S3), and the two values are compared. If the noise continues and the current count value exceeds the upper limit of the allowable range (S2, S3).
4), (14) Since the second cycle, the previous count value update stop time is not "0" (S5). (15) Since the previous count value update stop time is set to A for the second cycle, NO is determined in the step S6, and the previous count value (e in FIG. 4) at which the update is stopped is output (S1).
0).

(16) If noise disappears after (15) and the current count value (h in FIG. 3) falls within the allowable range (S2, S3, S4), (h and e in FIG. 3) (Comparison) (17) After S7 and S8, the current count value (h in FIG. 3) is output (S10).

Next, a case where a pulse which actually detects radiation or the like instead of noise is input and the count rate increases,
This will be described with reference to FIG. (18) Up to the above (15), it is the same as the case where noise occurs over two cycles. (This time count value f,
For g, the output is the previous count value e, e at which updating was stopped.
Is output)

(19) The present count value in the third cycle (FIG. 5)
H) and the previous count value (e in FIG. 5) are read (S
2, S3), comparing the two, if the current count value exceeds the upper limit of the permissible range (S4), (20) Since it is the third cycle, the previous count value update stop time is not “0” ( S5), (21) Since the last count value update stop time A is set to two cycles, the third cycle becomes YES in step S6, and the current count value (h in FIG. 5) is output (S1).
0).

(22) Thereafter, if the current count value further exceeds the upper limit of the allowable range, S2 to S6 and S10 are repeated to output the current count value. (23) Then, in step S4, if the current count value falls within the allowable range, the update stop of the previous count value (e in FIG. 3) is released via S7 (S8), and the current count value is output (S8). S10), returning to the processing operation from the above (1).

In the first embodiment, when the current count value exceeds the allowable range, the update of the previous count value is stopped during a period that is a multiple of the fixed period, and as a result the upper limit of the allowable range is fixed. Even when noise enters at the boundary of, or when the noise count in each sampling fluctuates, the transient noise can be reliably removed. Further, since the allowable range is set based on the previous count value, there is an advantage that it can follow a gradual change in the input count value due to the temperature characteristics of the detector and the like.

Embodiment 2 In the first embodiment, even if step S6 in FIG. 2 is YES (and the current count value is equal to or more than the upper limit of the permissible range based on the comparison result between the current count value and the previous count value at which the update is stopped), the previous count value remains unchanged. In the second embodiment, the number of times (period) in which the output of the previous count value is continued is limited, and thereafter, the present count value and the previous count value after the update stop is canceled are output. In this case, the processing returns to the normal operation processing that operates based on the comparison result.

FIG. 6 is a flow chart of this embodiment, in which steps T7 and T8 are added to FIG.
The main part of this operation will be described. (1) The set value B of the period is set under the condition of B> A.

(2) As a result of the comparison between the current count value and the previous count value in step T4, if the current count value continues to exceed the upper limit of the permissible range, the "previous count value update stop time A" is reached in step T6. Up to this time, the previous count value at the time when the update was stopped is output (T13). (3) In the step T6, "the last count value update stop time>
If "A", step T7 becomes NO and the current count value is output (T12).

(4) Further, as a result of the comparison between the current count value and the previous count value in step T4, the state where the current count value exceeds the upper limit of the allowable range continues, and in step T7, "previous count value update stop time = B" Then, the last count value update stop is released, the last count value update stop time is reset (T8), (5) After outputting the current count value (T12), the initial current count value and the previous count value are output. The process returns to the processing operation based on the comparison result with.

FIGS. 7 and 8 show the relationship between the count value and the judgment output. FIG. 7 shows a case where the number of pulses to be measured increases, where A is set to twice the fixed period (sampling period) and B is set to six times the fixed period. Since the current count value exceeds the upper limit of the allowable range when the count value is b or c, the period A
During (two periods), the previous counts a and a at the time of updating stop are output.

Further, as a result of comparison between the current count value and the previous count value, if the current count value exceeds the upper limit of the allowable range, the current count value is output as it is during the period B after the period A, and the count rate is calculated. An increase can be observed. Then, after the elapse of the period B, a count value based on a comparison result of the first current count value and the previous count value is output to obtain a count rate. Therefore, even if noise such as the current count value i is mixed, it can be removed.

FIG. 8 shows the case where the level returns to the normal low count value level after the noise is mixed and further noise is mixed. When the current count values b and c include noise, the previous count values a and a at the time when the update is stopped are output. In the period B after the period A has elapsed, the current count value d is within the allowable range. The output of the determination block is obtained, and thereafter, the process returns to the first process based on the comparison between the current count value and the previous count value.

As described above, even when the radiation level of the measurement object changes, noise can be removed.

Embodiment 3 In the first embodiment, the case where the current count value 21 is compared with the previous count value 31 has been described. However, as shown in FIG.
Instead of 1, a previous negative feedback count value 51 may be provided and compared with the current count value.

In this way, it is possible to reduce the fluctuation of the upper limit of the allowable range and increase the resolution of noise discrimination.
The upper limit of the allowable range of the determination block 32 is set as follows using, for example, the set standard deviation.

Upper limit of allowable range: 3 × (previous negative feedback count value) ^1/2 + (previous negative feedback count value) = 3 × (ΔN ′ _B ) ^1/2 + ΔN ′ _B −−−− (9)

Embodiment 4 In the first embodiment, the method of removing the transient noise when the current count value 21 exceeds the upper limit of the allowable range has been described. However, this embodiment uses a time constant To increase the response of the counting rate measurement.

FIG. 10 is a block diagram of this embodiment.
A standard deviation switching block 61 is provided, and a determination result of the lower limit of the allowable range of the determination block 32 is input. When the lower limit of the allowable range continues for an integral multiple of a fixed period, the standard deviation is switched to change the count rate calculation block 23. Then, the count rate calculation block 23 inputs the switched standard deviation and calculates the count rate with the speed time constant.

In this way, the counting rate can respond quickly to a sudden decrease in the number of pulses to be measured. The lower limit of the allowable range of the determination block 32 is set to, for example, 0. Switching the standard deviation σ is equivalent to γ as in equations (10) and (11).
And the counting rate calculation can be executed with the speed time constant. ^{σ = (1 / 2nτ) 1/2} = (r / 2) 1/2 = (2 -X-1 · ln2) 1/2 ------ (10) n = F B (M) = e ^rM = 2 ^{rM / ln2} −−−−−− (1
1) However, r = 2− ^x · ln2

When γ of the standard deviation switching block 61 is switched, M of the integrating block 22 is also replaced at the same time so that γM of the counting rate calculation in the counting rate calculating block 23 becomes the same value as before switching. Start the calculation of

The previous count value 31 in FIG. 10 can be replaced with the previous negative feedback count value 51 as in the third embodiment.

FIG. 11 is a flowchart showing the procedure of the arithmetic processing, which will be described. (1) Set standard deviation = σ1 (for normal time constant), initialize the number of times below the lower limit of the allowable range (U1), (2) Current count value (ΔN _IN ) and previous count value (Δ
_N'IN ) and (U2),

(3) (ΔN _IN <α × ΔN ′ _IN ) where α is a constant and the two are compared.
4), (4) Go to step U8, and count the number of times equal to or less than the lower limit of the allowable range =
Since it is 0, (5) a normal calculation for calculating the count rate is executed (U1
3). Usually, the above steps U2, U3, U4, U8,
Repeat U13.

(6) Next, in step U4, if the current count value is equal to or smaller than the lower limit of the allowable range, the standard deviation = σ
2 If it is not (for speed time constant) (U5), (7) Since the number of times equal to or less than the lower limit of the permissible range is the first time, the set value does not become C (U6), and (8) a normal operation is executed (U13) ).

(9) When the number of times equal to or lower than the lower limit of the allowable range continues in step U4 and the number of times equal to or lower than the lower limit of the allowable range = C in step 6, (10) the standard deviation is switched from σ1 to σ2 (U
7). The setting of the time constant is (standard deviation σ2
> Standard deviation for normal time constant σ1)

(11) A previous integrated value M 'is obtained from the standard deviation σ2 after switching and the previous count rate n' (U12). (12) Thereafter, a normal operation is performed (U13).

(13) If the number falls within the allowable range before the number of times equal to or less than the lower limit of the allowable range = C, the process goes from step U4 to U8, where 0 <the number of times equal to or lower than the lower limit of the allowable range <C. ) Reset the number of times below the allowable lower limit (U
9), (15) Confirm that the standard deviation is σ2 (U1
0), (16) The standard deviation is switched to σ1 (U11). (17) Then, the operations of steps U12 and U13 are executed.

By switching the standard deviation as described above, the time constant can be changed, and the response of the counting rate measurement can be made faster.

Although the time constant is switched stepwise, the time constant may be changed according to the lower limit of the allowable range and the duration thereof.

Embodiment 5 In the above-described fourth embodiment, the method of speeding up the response of the decrease in the count rate when the current count value 21 becomes equal to or less than the lower limit of the allowable range has been described. In this embodiment, as shown in FIG. A determination result of whether or not the value is equal to or smaller than the lower limit of the allowable range of the determination block 32 is input. If the lower limit of the allowable range continues for an integral multiple of a fixed period, a failure alarm is issued.

This makes it possible to minimize the delay in issuing an alarm, and to issue an earlier alarm than the conventional alarm issuance based on a decrease in the measured value of the count rate. Note that the lower limit of the allowable range of the determination block 32 can be realized by setting the lower limit to, for example, 0.

The previous count value 31 in FIG. 12 can be replaced with the previous negative feedback count value 51 as in the third embodiment.

Embodiment 6 FIG. In the first embodiment, the method for improving the problem during the normal operation has been described. However, as shown in FIG.
Is input to the determination block 32 to bypass the determination, thereby preventing a malfunction due to a sudden change in the input count value during the test. Noise removal block 33 in FIG.
Can be applied in combination with the fourth and fifth embodiments by replacing the standard deviation switching block 61 and the alarm block 81.

[0065]

【The invention's effect】

(1) As described above, according to the present invention, when a noise pulse enters, a count value due to noise is not counted, so that erroneous counting due to noise can be prevented.

(2) Since the time constant is changed when the count of the pulse to be measured decreases, the response can be made faster.

(3) Since the alarm signal is sent when the count of the pulse to be measured decreases, the alarm can be issued early.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a flow of a calculation process according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure of a calculation process according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a determination block output process according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a determination block output process according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a determination block output process according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating a procedure of a calculation process according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating a determination block output process according to the second embodiment of the present invention;

FIG. 8 is a diagram illustrating a determination block output process according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing a flow of a calculation process according to the third embodiment of the present invention.

FIG. 10 is a block diagram showing a flow of a calculation process according to a fourth embodiment of the present invention.

FIG. 11 is a flowchart illustrating a procedure of a calculation process according to the fourth embodiment of the present invention.

FIG. 12 is a block diagram showing a flow of a calculation process according to the fifth embodiment of the present invention.

FIG. 13 is a block diagram showing a flow of an arithmetic processing according to the sixth embodiment of the present invention.

FIG. 14 is a block diagram showing a conventional digital count rate meter.

FIG. 15 is a block diagram showing a flow of an arithmetic processing of an arithmetic unit in a conventional digital count rate meter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Counter 2 Computing device 3 Output count rate 21 Current count value 22 Integration block 23 Count rate integration block 24 Negative feedback block 25 Control block 31 Previous count value 32 Judgment block 32 Noise removal block 51 Previous negative feedback count value 61 Standard deviation switching block 81 Alarm block 91 Test status signal

Claims (8)

[Claims] 1. A counting rate meter having a counter for counting the number of pulses to be measured for each sampling period, and deriving a counting rate based on a count value of the counter.
Comparing means for comparing the current count value of the counter with the previous count value to determine whether or not the current count value is within the allowable range; and A count rate is obtained based on the value, and in a state where the present count value exceeds the upper limit of the allowable range in the comparison result, the previous count value at the time when the count value exceeds the upper limit is fixed, and the previous count value of the comparing means is fixed. The previous count value is used to compare with the present count value, and the count rate is calculated using the fixed previous count value within a predetermined period, and after the predetermined period, the count rate is calculated using the current count value. When the current count value exceeds the upper limit of the allowable range and the current count value falls within the allowable range, the comparison means does not use the fixed count value. Digital counting rate meter, characterized by comprising a calculating means for the return to the comparison process. 2. A counting rate meter having a counter for counting the number of pulses to be measured for each sampling period, and deriving a counting rate based on a count value of the counter.
Comparing means for comparing the current count value of the counter with the previous count value to determine whether or not the current count value is within an allowable range; and calculating means for determining whether the current count value is within the allowable range based on the comparison result. For example, a count rate is obtained based on the current count value, and in a state where the current count value exceeds the upper limit of the allowable range in the comparison result, the previous count value at the time when the count value exceeds the upper limit is fixed, and the previous count The value is compared with the current count value using the fixed previous count value, and the count rate is determined using the fixed previous count value within a predetermined period, and the allowable range is determined after the predetermined period has elapsed. If the state continues to exceed the upper limit, the count rate is calculated using the current count value for a certain period, and if the above-mentioned certain period has elapsed or the current count value has exceeded the upper limit of the allowable range. When al current count value is in a state within the tolerance range, digital counting rate meter, characterized by comprising a calculating means for the return to the comparison processing which does not use the count value of said fixed the comparing means. 3. The digital counting rate meter according to claim 1, wherein the counting rate meter has a counter for counting the number of pulses to be measured for each sampling cycle, and the current count value of this counter is provided. Is subtracted from the previous negative feedback count value (the product of the previous count rate and the time of one sampling cycle) to obtain a difference, algebraically integrates the difference, and derives a count rate based on the integrated value. A digital count rate meter characterized in that when a counter is used, a previous negative feedback count value is used instead of the previous count value. 4. A counting rate meter having a counter for counting the number of pulses to be measured for each sampling period, and deriving a counting rate based on the count value of the counter.
A digital count rate meter comprising a time constant changing means for increasing a time constant for calculating a count rate when the count value becomes equal to or less than a lower limit of an allowable range and continues for a predetermined period. 5. The digital counting rate meter according to claim 1, further comprising a time constant changing means for the digital counting rate meter according to claim 4. Total. 6. The digital counting rate meter according to claim 1, further comprising an alarm means for outputting an alarm signal when the current count value becomes equal to or less than the lower limit of the allowable range and continues for a predetermined period. A digital counting rate meter, characterized in that: 7. The digital count rate meter according to claim 1, wherein the allowable range is a value based on a standard deviation of the count rate. 8. The digital counting rate meter according to claim 1, wherein a current count value is directly input to a calculating means, bypassing the comparing means, when testing. Rate meter.