JP2703469B2 - Digital radiation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radiation measurement and, more particularly, to a digital radiation measurement apparatus which performs high-speed and high-precision signal processing by using a low-bit precision or high-speed AD converter.

[0002]

2. Description of the Related Art As shown in a block diagram of FIG. 17, digital signal processing in a conventional radiation measuring apparatus converts an analog signal 2 from a radiation detector 1 into an N-bit accurate AD signal.
It is necessary to convert the signal into a digital signal 4 using the converter 3 and to perform a desired operation using the operation circuit 5 to obtain the operation result 6 of the AD conversion.

[0003]

When an analog signal 2 from a radiation detector 1 is converted into a digital signal 4 using an AD converter 3 having an N-bit conversion accuracy, the obtained digital value is an AD value. It has a discrete value of N-bit accuracy based on the conversion accuracy of the converter 3. Therefore, it is difficult to obtain an operation result 6 with N-bit precision or more even if the digital conversion value thus obtained is subjected to digital operation processing by the operation circuit 5.

Therefore, as a measure to solve this problem, an AD converter with high bit precision must be used. However, it is difficult to obtain an AD converter with high accuracy in a conversion time of about several ns. There was a problem that it was very expensive. In the field of radiation spectroscopy, it is necessary to obtain an operation result with an accuracy of at least 12 bits or more, but an AD having a conversion time of several ns is required.
The accuracy of the converter is generally about 8 bits, and it has been difficult to measure the spectrum with high accuracy by the conventional method.

Further, in order to extract a signal related to the radiation from the radiation detector 1, the output signal of the radiation detector 1 is usually differentiated. A differentiating circuit having a long time constant as described above is required. Therefore, when the amount of incident radiation is large, measurement accuracy has been an issue.

An object of the present invention is to use an A / D converter with low bit precision or a high-speed A / D converter so that the operation result has the required bit precision, and immediately after data acquisition, An object of the present invention is to provide a digital radiation measuring apparatus capable of performing high-speed and high-accuracy signal processing by charging and resetting a differentiation capacitor having a relatively long time constant.

[0007]

A differentiation circuit for inputting an analog detection signal, an addition circuit for adding an analog correction signal to the differentiation output signal, an AD conversion circuit for digitally converting the addition signal of the addition circuit, and a digital signal An arithmetic circuit for shaping the waveform, a memory circuit for storing the result of the arithmetic processing and outputting a data storage end signal, a reset circuit operated by the data storage end signal, and the differentiation circuit according to a reset signal from the reset circuit. A
The D conversion circuit and the arithmetic circuit are reset.

A differentiating circuit for inputting an analog detection signal and a first AD for converting the differential output signal at a high speed.
A converter, a D / A converter for converting the converted digital signal into an analog signal, a differential amplifier for amplifying a difference between the digital output signal and the differential output signal, a second A / D converter for performing an A / D conversion of the output signal, and A high-speed and high-precision AD converter comprising an AD conversion output circuit for outputting an AD conversion result by combining output signals of the first and second AD converters; an arithmetic circuit for waveform shaping the digital signal of the output; A memory circuit for storing the operation processing result and outputting a data storage end signal, a reset circuit operated by the data storage end signal, and a differential circuit, a high-speed and high-precision AD converter and an arithmetic circuit, It is characterized by resetting.

The high-speed and high-precision AD converter is
A changeover switch for switching between a differential output signal from a differentiating circuit and an output signal of a differential amplifier;
A D converter, a D / A converter for converting the converted digital signal into an analog signal, a hold circuit for holding the differential output signal in an analog manner, and amplifying a difference between an output signal of the D / A converter and an output signal of the hold circuit. And an AD conversion output circuit that receives the output signal of the AD converter and processes the conversion result.

[0010]

According to the first aspect of the invention, the analog signal input from the detector is differentiated by the differentiating circuit, and the adding circuit adds, for example, a ramp-shaped analog correction signal. The addition signal is digitally converted by the AD conversion circuit, and further subjected to waveform shaping by the arithmetic circuit, and the arithmetic processing result is stored in the memory circuit.

In the memory circuit, with the end of data storage,
A data storage end signal is issued to the reset circuit, and a reset signal is transmitted from the reset circuit to the differentiating circuit, the AD conversion circuit, and the arithmetic circuit. By resetting these signals, a detection state for the next input signal is prepared. . As a result, the input analog signal becomes A with low bit precision.
Even if a D conversion circuit is used, high-speed and high-precision arithmetic processing results can be obtained.

In the second invention, the analog signal input from the detector is differentiated by a differentiating circuit, and is digitally converted by a first AD converter of a high-speed and high-precision AD converter.
The analog signal is converted by a DA converter. The difference between the analog output signal and the differential output signal from the differentiating circuit is calculated by the differential amplifier.

The output signal of the differential amplifier is digitally converted by a second AD converter, and the digital output and the digital output from the first AD converter are combined by an AD conversion output circuit and output to an arithmetic operation circuit. You. Further, the digital conversion result is waveform-shaped by an arithmetic circuit, and the arithmetic processing result is stored in a memory circuit.

In the memory circuit, with the end of data storage,
A reset signal is sent to the reset circuit, and the reset circuit transmits the reset signal to the differentiating circuit, the high-speed and high-precision AD converter, and the arithmetic circuit, and resets them to detect the next input signal. In addition, the input analog signal can obtain a high-speed and high-precision arithmetic processing result even if an AD conversion circuit with low bit precision is used.

[0015]

An embodiment of the present invention will be described with reference to the drawings. The same components as those of the above-described conventional technology are denoted by the same reference numerals, and detailed description thereof will be omitted. The first invention is
As shown in the block diagram of FIG. 1, the analog signal 2 input from the radiation detector 1 becomes a differential signal 8 via a differentiating circuit 7. The time constant of the differentiating circuit 7 needs to be increased to some extent in order to accurately measure the analog signal 2 from the detector having a slow rise time.

An addition circuit 9 adds an analog correction signal 10 to the differential signal 8, and the addition signal 11 is digitally converted by an AD converter 12. The digital signal 13 converted here
The arithmetic circuit 14 performs arithmetic processing, and the output arithmetic processing result 15 is stored in a memory location of the memory circuit 16 corresponding to the arithmetic processing result 15.

When data storage by the memory circuit 16 is completed, the memory circuit 16 immediately outputs a memory end signal 17
Is output. The reset circuit 18 is driven by the memory end signal 17 and generates a pulse signal as the reset signal 19 for a time t. The reset signal 19 causes the A / D converter
12 and the digital value of the arithmetic circuit 14 are reset, and the resetting relay 20 connected to the differentiating circuit 7 is closed to reset the differentiating circuit 7.

FIG. 3 is a circuit diagram showing details of the differentiating circuit 7 and the adding circuit 9. In the differentiating circuit 7, the analog signal 2 is differentiated by a time constant determined by a differentiating capacitor 21 and a differentiating resistor 22. The differential signal 8 of the analog signal 2 is generated at the output of the operational amplifier 23 to which this is input.

In order to accurately measure a detector signal having a slow rise, the time constant of the differentiation (the value of the differentiation capacitor 21 × the resistance of the differentiation resistor 22) is sufficiently long that the differentiation signal 8 becomes flat within the analysis time. Value). In this case, the differential gain is (value of feedback resistor 24) /
(The value of the differential resistor 22). A reset resistor 25 is connected to the reset relay 20.

The adder circuit 9 comprises an operational amplifier 26 for adding the differential signal 8 and the analog correction signal 10 and resistors 27, 28 and 29. The differential signal 8 and the analog correction signal 10 which are input are added and added. The signal 11 is converted into a digital signal 13 by a high-speed AD converter 12 with a low bit accuracy of about 8 bits.
Is converted to

An arithmetic circuit 14 for performing arithmetic processing on the digital value obtained by the conversion is provided at the subsequent stage of the AD converter 12.
Is connected. The arithmetic circuit 14 comprises a digital filter having an integrating function. The arithmetic processing result 15 obtained by shaping the waveform of the digital signal 13 and integrating over time is used as a memory circuit.
Save to 16.

When the output signal of the arithmetic circuit 14 is stored in the memory circuit 16, the data measurement of one given input signal is completed. Therefore, the reset circuit 18 is operated by the memory end signal 17 at this time. Then, a reset signal 19 for a pulse period t is generated as an output,
At 19, the AD converter 12 and the arithmetic circuit 14 are digitally reset.

At the same time, a reset signal 19 is output from a reset relay 20 provided in the differentiating circuit 7 operating in analog.
And a differentiation capacitor through a reset resistor 25
The differential signal 8 is obtained by charging 21 in a short time.
Is configured to reset.

To reset the differentiation signal 8 by charging the differentiation capacitor 21 in a short time, the reset time constant of (value of the differentiation capacitor 21) × (value of the reset resistor 25) is set to ( The reset resistor 25 is set so as to be sufficiently smaller than the differentiation time constant of (the value of the differentiation capacitor 21) × (the value of the differentiation resistor 22).

Although the differentiating circuit 7 shown in FIG. 3 is based on the operational amplifier 23, the C circuit shown in the circuit diagram of FIG.
The same operation can be obtained as a differentiating circuit using -R. In this case, the differential signal 8 is generated by differentiating the differential capacitor 30 and the differential resistor 31. The reset relay 20 is inserted in series with the reset resistor 32, and the reset time constant is given by (the value of the differential capacitor 30) × (the value of the reset resistor 32), and this time constant becomes sufficiently small. The reset resistor 32 as described above.

Next, the operation of the above configuration will be described. First, regarding the A / D conversion which is the first feature of the first invention, as shown in the characteristic diagram of FIG. 5, the differential output signal 8 has a digital value range "L, L + 1 ", if there is no correction signal 10 in the adder circuit 9, this range" L, L +
Even if the waveform of the differential output signal 8 changes within "1", it does not affect the digital value of the output of the AD converter 12.

Therefore, even though the differential signal 8 has not changed, the result of the operation on the digital conversion value obtained always has the same value. Note that the range “L, L + 1” corresponds to AD
This is the minimum section that the converter 12 can digitize, and is called 1 LSB (least significant bit).

On the other hand, in the present invention, FIG.
As shown in (1), by adding the analog correction signal 10 to the differential signal 8, the AD conversion accuracy is improved. That is, as an example of the correction signal 10, as shown in the correction signal characteristic diagram of FIG. 6, there is a ramp-shaped correction signal 33 which reaches 0 to 1 LSB in the analysis time T in the arithmetic circuit 14.

The characteristic diagram of FIG. 7 shows the waveform of the addition signal 11 from the addition circuit 9 when the ramp-shaped correction signal 33 is applied. FIG. FIG. 7B shows a case where the differential signal 35 is (L)
The case of a voltage slightly smaller than +1) is shown.

When there is no correction signal 33, FIG.
(B) In both cases, the AD conversion value is L, and even if this is integrated for T time, both values are the same. However, when the ramp correction signal 33 is applied, in the t ₁ hour later case of FIG. 7 (a) beyond the level of the (L + 1), shown by the shaded area
It becomes 36.

On the other hand, in the case of FIG.
Area beyond the more fairly early t ₂ hours later (L + 1)
Enter 36. Therefore, if the digital values from time 0 to time T are integrated, even if the differential output signal 8 is in the range “L, L +
Even if the value is "1", the time during which the converted value of the AD converter 12 exceeds (L + 1) changes depending on the magnitude of the voltage, so that the bit precision of the operation result can be improved.

Next, the operation of the reset signal, which is the second feature, will be described. In FIG. 1, the AD converter 12
Is applied to an arithmetic circuit 14, and the arithmetic circuit 14 is constituted by a digital filter.
Contains an element that integrates the conversion result.

Therefore, if the result of the arithmetic processing 15 by the integration operation in the arithmetic circuit 14 is completed and this data is stored in the memory circuit 16, the information of the input signal given from the radiation detector 1 becomes unnecessary. Therefore, the reset signal 18 is generated by operating the reset circuit 18.

The reset signal 19 is a pulse signal having a pulse width t. The reset signal 20 is used to drive the reset relay 20 inserted in the differentiating circuit 7 and to use the digital circuit of the AD converter 12 and the arithmetic circuit 14. Reset so that the next input signal can be measured.

The reset characteristic diagram of FIG. 8 shows the case where (a) does not perform resetting, and (b) shows the case where there is a reset signal 19. The differential output signal 8 of the differentiating circuit 7 and the AD converter are respectively shown.
12 illustrates a temporal change of 12 digital signals 13 and an arithmetic processing result 15 from an arithmetic circuit 14.

The differential output signal 8 of the differentiating circuit 7 when resetting is not performed as shown in FIG. 8 (a) rises sharply, and it is necessary to accurately measure even the slowly rising analog signal 2 from the radiation detector 1. Differentiating with a long time constant, the differential output signal 8 drops very slowly. The differential output signal 8 is converted into a digital signal 13 by the AD converter 12 after the correction signal 10 is added by the adding circuit 9.

Digital signal output from AD converter 12
13 is shaped by an arithmetic circuit 14 constituting a digital filter, and an arithmetic processing result 15 is generated. In the case where the reset is not performed in this way, if a sufficient time elapses due to a large differential time constant and the next differential output signal 8 is added before the differential output signal 8 returns to a predetermined voltage, the differential output signal 8 8 may not be measured correctly.

On the other hand, when resetting is performed by the reset signal 19 as shown in FIG. 8B, the differential output signal 8 of the differentiating circuit 7 and the output of the AD converter 12 are output before the reset signal 19 is applied. The generation of the digital signal 13 and the arithmetic processing result 15 from the arithmetic circuit 14 is the same as that in the case of FIG. 8A, but if the data is stored in the memory circuit 16, the differential output signal 8 is not Required.

Therefore, the reset circuit 18 generates a pulse-shaped reset signal 19 for a time t to reset the digital signal 13 of the A / D converter 12 and the operation processing result 15 of the operation circuit 14 as shown in FIG. The differential output signal 8 is set to zero by closing the reset relay 20 and charging the differential capacitor 21 constituting the differentiating circuit 7. Therefore, even if the next signal comes in after the reset signal 19 is applied, the measurement can be performed correctly.

Further, high-speed and high-precision AD conversion using a correction signal, which is a main part of the first invention, a differentiating circuit,
The converter and the high-speed reset of the arithmetic circuit will be described separately. The characteristic diagram of FIG. 9 shows the conversion accuracy when the 8-bit high-speed AD converter is used. FIG. 9A shows the differential signal, and FIG. 9B shows the digital integrated value for the differential signal.

In FIG. 9A, since the time constant of the differentiation is sufficiently long, the differentiated signal 34 having little change over time is converted into the range [L, L] of the digital conversion value by the 8-bit high-speed AD converter.
+1], if there is no correction signal, the digital conversion result does not change even if the value of the input voltage changes from the lower limit to the upper limit of this range.

As shown in FIG. 9B, as a digital operation process after AD conversion, integration of 128 points in the section [0,128] is considered. Assuming that there is no correction signal, the true integral value 37 when the differential signal 34 is continuously changed in the range [L, L + 1] is represented by a straight line [L × 128 to (L + 1) × 128].
It should change continuously within the range.

However, when the integral of the differential signal 34 is obtained by digital operation, the differential signal 34 is 1LS in the range [L, L + 1].
Even if it changes continuously within B (least significant bit), the digital conversion value does not become a value other than L.
It becomes 8. Similarly, the differential signal 34 is in the range [L + 1, L + 2].
, The digital integration result is (L + 1) × 128.

That is, when integrating a digitized value using an 8-bit precision AD converter, an integrated signal
Even if 37 changes continuously, the digital integration result is not a continuous value but a discrete 8-bit precision value.

However, as shown in FIG. 6, a ramp-shaped correction signal is added to the differential output signal 8 by an adder 9.
When 33 is applied, the amplitude of the ramp correction signal 33 changes in the section [0,
128], the digital integration result is differentiated even if the differential signal 34 is in the range [L, L + 1] as described with reference to FIG. It changes according to the magnitude of the signal.

The characteristic diagram of FIG. 10 shows that the differential signal is in the range [L, L
+1] shows the relationship between the digital integrated value and the differentiated signal level for the case where the value changes between +1] and the integral value is proportional to the differentiated signal level. Therefore, since the differential signal level can be obtained from the integrated value, if the added signal after correction is digitally converted and then digitally integrated in the section [0,128], the digital conversion value changes due to the effect of the added correction signal 38. , The bit precision can be improved.

That is, the bit precision of the operation result is the length of the integration interval, the number of additions of the digital value, and the correction signal.
Because it can be determined by the slope of 38, 8-bit A
Despite the use of the D converter, the calculation accuracy can be improved to 8-bit accuracy or more. Note that, as shown in the correction signal characteristic diagram of FIG.
(A) a sawtooth wave 39 or (b) a triangular wave 40 can also be used.

Next, the operation of the reset signal 19 will be described. After the operation processing result 15 output from the arithmetic circuit 14 in FIG. 3 has been stored in the memory circuit 16, a pulse-like reset signal 19 is generated from the reset circuit 18.
The D converter 12 and the arithmetic circuit 14 are digitally reset. At the same time, the reset signal 19 activates the reset relay 20 inserted in the analog differentiating circuit 7 to charge the differentiating capacitor 21 within a short time.

Therefore, the value of the resetting resistor 25 needs to be sufficiently smaller than the value of the differentiating resistor 22 so that the differentiating capacitor 21 can be charged in a short time. The operation status of the reset signal 19 in the differentiating circuit 7 and the temporal behavior of the differential output signal 8 are as shown in FIG.
Since the reset relay 20 needs to operate in about several microseconds, it is desirable to use a semiconductor switch.

According to the first invention, conventionally, the analog signal 2 from the radiation detector 1 or the like is converted into a digital value by an AD converter having a low bit precision (for example, 8 bits) without a correction signal. Also, the digital value obtained when the digital integration operation processing is performed is a discrete value of 8-bit accuracy, but the digital integration operation result of 8-bit accuracy or more can be obtained by adding the correction signal 10 such as a ramp. , And after the data is stored, the differentiating circuit 7, A
By resetting the D converter 12 and the arithmetic circuit 14, high-speed and high-accuracy digital signal processing becomes possible, and the accuracy of radiation detection is greatly improved.

According to the second aspect of the present invention, as shown in the block diagram of FIG. 2, the analog signal 2 from the radiation detector 1 is input to a differentiating circuit 7 to output a differential output signal 8.
To accurately measure an input signal from a detector having a slow rise time, the time constant of the differentiating circuit 7 needs to be increased to some extent.

Although the differential output signal 8 from the differentiating circuit 7 has a low bit precision, it has a high-speed AD conversion circuit, a DA conversion circuit, a differential amplifier and an AD conversion output circuit.
The differential output signal 8 is applied to a high-precision A / D converter 41 to convert the differential output signal 8 into a digital signal with an accuracy of 12 bits or more in about several seconds.
Convert to 42.

An arithmetic circuit 14 converts the converted digital value.
To perform the arithmetic processing, and output the arithmetic processing result 15,
The arithmetic processing result 15 is stored in the memory location of the memory circuit 16 corresponding to the output. The memory circuit 16 issues a memory end signal 17 immediately after the storage of the memory is completed, drives the reset circuit 18, and outputs the reset signal 19 at time t.
During this time, a pulse signal is generated.

The reset signal 19 is a high-speed and high-precision AD signal.
The converter 41 is configured to reset the digital value of the arithmetic circuit 14 and to operate the reset relay 20 inserted in the analog differentiating circuit 7.

FIG. 12 is a circuit diagram showing the details of the differentiating circuit 7 and the high-speed / high-precision AD converter 41. The analog signal 2 from the radiation detector 1 is input to the differentiating circuit 7 and the differential output signal 8 Is output. In order to accurately measure an input signal from a detector having a slow rise time, it is necessary to increase the time constant of the differentiating circuit 7 to some extent.

The differential output signal 8 from the differentiating circuit 7 has a low bit precision, but has a high-speed A / D conversion circuit, a D / A conversion circuit, a differential amplifier and an A / D conversion output circuit.
The differential output signal 8 is applied to a high-precision A / D converter 41, which converts the differential output signal 8 into digital
Convert to 42.

An operation circuit 14 converts the converted digital value.
To perform the arithmetic processing, and output the arithmetic processing result 15,
In the memory location of the memory circuit 16 corresponding to the output,
The calculation processing result 15 is stored. Immediately after the memory storage is completed, the memory circuit 16 issues a memory end signal 17 to drive the reset circuit 18, and generates a pulse signal as the reset signal 19 for a time t.

The reset signal 19 resets the digital values of the high-speed and high-precision AD converter 41 and the arithmetic circuit 14, and activates the reset relay 20 inserted in the analog differentiating circuit 7 to change the differential capacitor 21. It is configured to charge the battery within a short time and reset the differential output signal 8 of the differentiating circuit 7.

The analog signal 2 from the radiation detector 1
Is differentiated by a time constant determined by a differentiating capacitor 21 and a differentiating resistor 22 of the differentiating circuit 7, and a differential output signal 8 of the analog input signal 2 is generated at the output of the operational amplifier 23.

In order to accurately measure a detector signal having a slow rise, the time constant of the differentiation (differential capacitor) is sufficiently long that the differential output signal 8 becomes flat within the analysis time.
(Value of 21 × value of differential resistor 22). The differential gain in this case is given by (value of feedback resistor 24) / (value of differential resistor 22).

The differential output signal 8 is supplied to the first AD converter a43
And a DA converter 44, a differential amplifier 45, and a second AD converter b
High-speed and high-precision A consisting of 46 and AD conversion output circuit 47
The digital conversion is performed by the D conversion device 41 at high speed and high accuracy. The digital signal 42 from the high-speed and high-precision AD converter 41 is digitally filtered by the arithmetic circuit 14, and the arithmetic processing result 15 of the output is stored in the memory circuit 16.

The memory circuit 16 outputs a memory end signal 17 immediately after storing the data, and operates the reset circuit 18 to generate a reset signal 19. The reset signal 19 is in the form of a pulse of time t, and the reset signal 19 drives the reset relay 20 inserted in the differentiating circuit 7 to
At the same time as charging the differentiation capacitor 21 in a short time, the first AD converter a43, the DA converter 44, and the second
Is reset so that normal measurement can be performed for the next input signal.

In FIG. 12, the differential output signal 8 is the first AD
The digital output 48 of the first AD converter a43 having N-bit accuracy is output to the AD conversion output circuit 47 and is also applied to the high-speed DA converter 44.
The analog output 49 of the DA converter 44 and the differential output signal 8 are input to the differential amplifier 45, and the difference between the analog output 49 of the two signals and the differential output signal 8 is amplified.
50 is given to the second AD converter b46.

The 1 LSB (least significant bit) of the first AD converter a43 is AD-converted with M-bit precision by combining the differential amplifier 45 and the second AD converter b46. Therefore, the digital output 48 (N bits) from the first AD converter a43 is set as the upper bit, and the digital output 51 (M bits) from the second AD converter b46 is set as the lower bit. , An (N + M) -bit digital signal 42 is generated at the output from the AD conversion output circuit 47.

As for the differentiating circuit 7 in FIG. 12, the same operation can be obtained as the differentiating circuit by CR shown in the differential circuit diagram of FIG.
By adding the analog signal 2, a differential output signal 8 that can be reset as an output can be obtained. The differentiation time constant in this case is (value of differentiation capacitor 30) × (differential resistor 31)
), The time constant when the reset relay 20 is activated is (value of the differentiation capacitor 30) × (value of the reset resistor 32). Therefore, the reset resistor 32 is differentiating resistor 31
Set a sufficiently small value compared to.

Next, the operation of the second aspect of the present invention having the above-described configuration will be described by dividing the operation into high-speed and high-precision AD conversion and a reset signal. The block diagram of FIG. 13 shows the basic configuration of the high-speed / high-precision AD converter 41. The differential output signal 8 is N
The first A / D converter a43 has a precision of about 8 bits in order to satisfy the condition of high-speed processing.

The digital output 48 of the first AD converter a43
Is applied to the high speed DA converter 44. The analog signal 49 output from the DA converter 44 and the differential output signal 8 are connected to a differential amplifier 45.
And a differential amplifier 45 amplifies the difference between the two signals,
The output signal 50 is applied to a second AD converter b46.

Here, one LSB of the first AD converter a43 is used.
(Least Significant Bit) is AD-converted to M bits,
The gains of the differential amplifier 45 and the second AD converter b46 are adjusted. Thereby, the digital output of the first AD converter a43 is obtained.
If 48 (N bits) are processed as upper bits and the digital output 51 (M bits) of the second AD converter b46 is processed as lower bits, a (N + M) -bit digital output 51 is obtained.

In the characteristic diagram of FIG. 14, (a) shows the state of AD conversion in the first AD converter a43, and (b) shows the state of AD conversion in the second AD converter b46. In FIG. 14A, assuming that the differential output signal 8 is in the range "L, L + 1" of the digital output 48 converted by the first AD converter a43.
Even if the waveform of the differential output signal 8 changes within this range "L, L + 1", it does not affect the digital output 48.
Despite the change in the waveform of the differential output signal 8,
The obtained digital value is always the same value.

However, once the first AD converter a
The digital signal 48 converted at 43 is subjected to digital-to-analog conversion at the DA converter 44, and the difference from the differential output signal 8 is amplified at the differential amplifier 45. The amplified signal is added to the second AD converter b46. The second AD converter b46 converts one LSB of the first AD converter a43 into an M-bit digital signal.

Therefore, if the digital output 48 of the first AD converter a43 and the digital output 51 of the second AD converter b36 are combined, the first AD with low bit precision can be obtained.
Even if the converter a43 is used, the overall bit precision can be improved with the help of the second AD converter b46.

A reset operation which is the next feature of the present invention will be described. In FIG. 2, high-speed and high-precision AD conversion circuit
The digital signal 41 is applied to the arithmetic circuit 14. The arithmetic circuit 14 is composed of a digital filter.
Contains an element that integrates the conversion result. Therefore, if the integration operation in the arithmetic circuit 14 is completed and the data of the arithmetic processing result 15 is stored in the memory circuit 16, the information of the given analog signal 2 becomes unnecessary, and the reset circuit
Activate 18 to generate reset signal 19.

The reset signal 19 is a pulse signal having a pulse width t. The reset signal 19 is used to drive the reset relay 20 inserted in the differentiating circuit 7 and to use the high-speed / high-precision AD converter 41 and the arithmetic circuit. Reset the 14 digital circuits so that the next input analog signal can be measured.

FIGS. 8A and 8B are reset characteristic diagrams common to the first embodiment. FIG. 8A shows the case where there is no reset signal, and FIG. 8B shows the case where there is a reset signal.
3 shows a temporal change of the digital signal 42 of the high-speed / high-precision AD converter 41, the arithmetic processing result 15 of the arithmetic circuit 14, and the reset signal 19 of the reset circuit 18.

The differential signal 8, which is the output of the differentiating circuit 7 when the reset signal 19 shown in FIG. 8A is not applied, rises rapidly, and a long rising signal is required to accurately measure a slow rising signal from the detector. Differentiate by a constant. This differentiated signal 8 is converted into a digital signal 42 by a high-speed / high-precision AD converter 41.
Is converted to The digital signal 42 is shaped by the arithmetic circuit 14 constituting a digital filter, and an arithmetic processing result 15 is generated.

As described above, when the reset signal 19 is not present, the differential time constant is large, and if the next differential output signal is applied before the differential output signal 8 returns to a predetermined voltage after a sufficient time has elapsed, There is a possibility that the differential output signal cannot be measured correctly.

On the other hand, when there is a reset signal shown in FIG. 8B, before the reset signal 19 is applied, the differentiated output signal 8 from the differentiating circuit 7 and the digital signal of the high-speed / high-precision AD converter 41 are output. The signal 42 and the arithmetic processing result 15 of the arithmetic circuit 14 are the same as those in FIG.
If the data is stored in 18, the differential output signal 8 is not needed.

Therefore, a reset signal 19 in the form of a pulse is generated from the reset circuit 18 for a time t, so that a high-speed and high-precision A
The digital signal 42 of the D converter 41 and the arithmetic processing result 15 of the arithmetic circuit 14 are reset, and the reset relay 20 shown in FIG. The differential output signal 8 is set to zero. Therefore, after the reset signal 19 is applied, it is possible to correctly measure even if the next signal comes in.

The features of the second invention are that high-speed and high-precision A / D conversion is performed using the high-speed A / D converters 43 and 46 with low bit precision, and unnecessary signals after data storage are reset. This realizes a high-speed and high-accuracy radiation measurement device.

The analog signal 2 from the radiation detector 1 is
Differentiating capacitor 21 and differentiating resistor 22 in differentiating circuit 7
The differential output signal 8 is generated at the output of the operational amplifier 23. Also, differentiating circuit 7
Is (the value of feedback resistor 24) / (the value of differential resistor 22)
And a reset resistor is connected in series with the reset relay 20.
25 has been inserted.

The time constant when the reset signal 19 is applied and the reset relay 20 is driven is (differential capacitor 21
) × (value of the reset resistor 25), and this time constant is sufficiently smaller than the time constant of the differentiating circuit 7 ((value of the differential capacitor 21) × (value of the differential resistor 22)). Set to. When the values of the resistors and capacitors are set in this manner, as shown in FIG. 8B, the differentiation capacitor 21 is rapidly charged when the reset signal 19 is applied, and the differentiation output signal 8 is changed for a short time. Can be set to a predetermined voltage.

FIG. 15 shows the relationship between the AD conversion output circuit 47 and the outputs of the first AD converter a43 and the second AD converter b46 when N = 8 bits and M = 4 bits. In the illustration, the output 51 of the second A / D converter b46 is the lower 1 to 4 bits, and the output of the first A / D converter a43.
48 is added from 5 bits to 12 bits. Note that the combination of the differential amplifier 45 and the second AD converter b46 makes the first
1 LSB of the AD converter a43 is subjected to AD conversion with a resolution of 4 bits (M = 4).

The digital signal 42 digitally converted at high speed and high accuracy is applied to the arithmetic circuit 14. This arithmetic circuit
Numeral 14 performs digital filtering and has a digital integration function. The arithmetic processing result 15 of the arithmetic circuit 14 is stored in a memory circuit 16.

When the storage of the data, which is the result 15 of the arithmetic processing, is completed, the information on the input signal from the radiation detector 1 becomes unnecessary, so that the memory end signal 17 is output and the reset circuit 18 is operated to reset the reset signal. Generate 19 pulses.

Using the reset signal 19, the reset relay 20 inserted in the differentiating circuit 7 is driven to charge the differentiating capacitor, and the first AD converter a43 and the second AD converter a43 are used.
AD converter b46, DA converter 44, AD conversion output circuit 47
Then, the digital circuit of the arithmetic circuit 14 is reset so that the next input signal can be measured.

The analog signal 2 from the radiation detector 1 is
When the digital signal is converted into a digital signal by the high-speed, low-bit-precision first A / D converter a43, the resulting digital value becomes a low-bit-precision discrete value. Convert to analog.

Thereafter, the difference from the analog signal 2 from the radiation detector 1 is amplified, and A
The digital output is further converted to a digital output 48 of two sets of the first AD converter a43 and a digital output of the second AD converter b46.
By combining 51 in the AD conversion output circuit 47, high-speed and high-precision AD conversion can be realized by a high-speed and low-bit-precision AD converter.

Further, the result of the AD conversion is subjected to a digital operation by the operation circuit 14 as appropriate, and then the data is stored.
After storing the data, the differentiation circuit 7, the AD converter a43,
By resetting b46 and the arithmetic circuit 14, etc., high-speed and high-accuracy digital signal processing becomes possible.

FIG. 16 is a block diagram showing a high-speed and high-precision AD.
5 shows a modification of the conversion device. In this modification, one AD converter is used, and a changeover switch 52 is employed to obtain the same operation and effect as those of the high-speed and high-precision AD converter 41. The differential output signal 8 passes through the A side of the changeover switch 52 and is subjected to A / D conversion in addition to a high-speed A / D converter 53 with low bit precision. The digital output 54 of this AD converter 53
Are used as upper bits of the AD conversion output circuit 47 when the changeover switch 52 is on the A side.

The digital output 54 after the AD conversion is
The analog output signal 56 is converted by the DA converter 44 into an analog output signal 56. At this time, the analog value of the differential output signal 8 is simultaneously stored in the hold circuit 55. When the upper bit data is stored, the changeover switch 52 is switched to the B side.
Thereby, the differential amplifier 45 adds the analog output signal 56 of the DA converter 44 and the differential output signal 8 which is the output signal 57 from the hold circuit 55, and the differential amplifier 45 calculates the difference between the two input signals. Is amplified as appropriate.

At this time, since the changeover switch 52 has been switched to the B side, the output signal 58 of the differential amplifier 45 is AD-converted by the AD converter 53, and the result is inserted into the lower bit of the AD conversion output circuit 47. You. Now, changeover switch 52
Assuming that the bit precision of the AD converter 53 when A is on the A side and the bit precision of the AD converter 53 when the changeover switch 52 is on the B side is M, 1 LSB on the A side is 2 L on the B side. If the gain of the differential amplifier 45 is adjusted to be ^M , the bit precision of the AD conversion output circuit 47 can be made (N + M) bits.

The following are the embodiments of the second invention. "A high-speed and high-precision A / D conversion device switches between a differential output signal from a differentiator circuit and an output signal of a differential amplifier;
A converter, a DA converter that converts the converted digital signal into an analog signal, a hold circuit that holds the differential output signal in an analog manner, and amplifies a difference between the output signal of the DA converter and the output signal of the hold circuit. A differential amplifier,
3. An AD conversion output circuit which receives an output signal of the AD converter and processes a conversion result.
The described digital radiation measurement device ".

[0093]

As described above, according to the present invention, a high-speed and high-precision digital operation result can be easily obtained by using an AD converter having low bit precision. Further, by resetting a differentiating circuit having a long time constant after data acquisition, there is an effect that a high-speed and high-accuracy radiation measuring apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a radiation measuring apparatus according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a radiation measuring apparatus according to an embodiment of the present invention;

FIG. 3 is a circuit configuration diagram showing details of a differentiating circuit and an adding circuit of one embodiment according to the first invention.

FIG. 4 is a diagram illustrating a differential circuit using CR according to an embodiment of the present invention.

FIG. 5 is a characteristic diagram of one embodiment according to the first invention.

FIG. 6 is a characteristic diagram of a correction signal according to the first invention.

FIGS. 7A and 7B are sum signal characteristic diagrams according to the first invention (FIG. 7A shows a case where a differential signal is low, and FIG.

FIG. 8 is a reset characteristic diagram according to the first invention ((a) shows a case without resetting, and (b) shows a case with resetting).

FIG. 9 is a conversion accuracy characteristic diagram according to the first invention ((a) is a differential signal, and (b) is a digital integration with respect to the differential signal).

FIG. 10 is a characteristic diagram of a digital integrated value with respect to the differential signal after correction according to the first invention.

FIG. 11 is a characteristic diagram showing an example of a correction signal according to the first invention ((a) is a sawtooth wave, and (b) is a triangular wave).

FIG. 12 is a circuit diagram showing details of a differentiating circuit and a high-speed and high-precision AD converter according to an embodiment of the second invention.

FIG. 13 shows a high-speed and high-precision A according to an embodiment of the second invention;
FIG. 2 is a block diagram of a D conversion device.

FIG. 14 shows first and second A of an embodiment according to the second invention.
The characteristic diagram showing the conversion state in the D converter ((a) is the first diagram).
(B) is a second AD converter).

FIG. 15 is an explanatory diagram showing a relationship between an AD conversion output circuit of one embodiment according to the second invention and outputs of first and second AD converters.

FIG. 16 is a block diagram showing a modification of the high-speed / high-precision AD converter according to the second invention.

FIG. 17 is a block diagram of a conventional digital radiation measuring apparatus.

[Explanation of symbols]

1 ... Radiation detector, 2 ... Analog signal, 3,12,53 ... A
D converter, 4, 13, 42 ... digital signal, 5, 14 ... arithmetic circuit, 6 ... arithmetic result, 7 ... differential circuit, 8, 34, 35 ... differential output signal, 9 ... addition circuit, 10, 33, 38 … Correction signal, 11…
Addition signal, 15 ... calculation processing result, 16 ... memory circuit, 17 ...
Memory end signal, 18… Reset circuit, 19… Reset signal, 20… Reset relay, 21, 30… Differential capacitor, 22, 31… Differential resistor, 23,26… Operational amplifier, 24… Feedback resistor, 25, 32 ... Reset resistor, 27-29 ... Resistance, 36 ...
Area, 37… Integrated signal, 39… Sawtooth wave, 40… Triangle wave, 41…
High-speed / high-precision A / D converter 43, first A / D converter a,
44: DA converter, 45: Differential amplifier, 46: Second AD converter b, 47: AD conversion output circuit, 48, 51, 54 ... Digital output, 49, 56 ... Analog output signal, 50, 57, 58 ... output signal, 52 ... changeover switch, 55 ... hold circuit.

Claims (2)

(57) [Claims] 1. A differentiation circuit for inputting an analog detection signal, an addition circuit for adding an analog correction signal to the differentiation output signal, and an AD for digitally converting the addition signal of the addition circuit.
A conversion circuit, an arithmetic circuit for shaping the waveform of the digital signal, a memory circuit for storing an arithmetic processing result and outputting a data storage end signal, a reset circuit operated by the data storage end signal, and a reset from the reset circuit. A digital radiation measuring apparatus, wherein the differentiating circuit, the AD conversion circuit, and the arithmetic circuit are reset by a signal. 2. A differential circuit for inputting an analog detection signal, a first AD converter for AD-converting the differential output signal at high speed, and a DA for converting the converted digital signal to analog.
A converter, a differential amplifier for obtaining a difference between the analog output signal and the differential output signal, and a second amplifier for AD-converting the output signal.
A high-speed and high-precision AD converter comprising an A / D converter and an A / D conversion output circuit for outputting an A / D conversion result by combining the output signals of the first and second A / D converters, and waveform shaping the digital signal of the output. Operation circuit, a memory circuit for storing an operation processing result and outputting a data storage end signal, a reset circuit activated by the data storage end signal, and the differentiation circuit, a high-speed and high-precision AD conversion by a reset signal from the reset circuit. A digital radiation measuring device, wherein the device and the arithmetic circuit are reset.