JPH0577035B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a structure of a radiation dosimeter that is easy to calibrate.

[Prior art and its problems]

FIG. 2 is a configuration diagram of a conventional radiation dosimeter, and FIG. 3 is an explanatory diagram of waveforms of important parts in FIG. Second
In the figure and FIG. 3, 1 is a radiation detector such as an ionization chamber that outputs a pulsed electric signal 1a every time radiation 2 is incident, and 4 is a pulse signal 1a whose width has been changed by an image width unit 3. This is a frequency dividing circuit that inputs a pulse signal 4a whose number of pulses has been reduced by a predetermined ratio to the calibration circuit 5. 6 is a NOR circuit into which the pulse signal 4a and the output signal 7a of the inverter circuit 7a are input; the output terminal of the NOR circuit 6 is connected to the input terminal of the inverter circuit 7 via the capacitor 8; A variable resistor 9g is connected between the positive potential 10 and the positive potential 10. Reference numeral 11 denotes a NAND circuit which receives the constant-frequency reference pulse 12a output from the oscillator 12 and the signal 7a and outputs an output signal 11a;
is composed of the above-described NOR circuit 6, inverter circuit 7, capacitor 8, variable resistor 9, positive potential 10, NAND circuit 11, and oscillator 12.

The calibration circuit 5 has been calibrated as described above and operates as described below. That is, the output signal 4a of the frequency divider circuit is at the L level when no pulse is output, and therefore the output level of the NOR circuit 6 is at the H level, so the input terminal of the inverter 7 is also at the level of the positive potential 10. , that is, at H level. Therefore, the output signal 7a is at L level, and the output signal 11a of the NAND circuit is also at L level. When a pulse is output from the frequency dividing circuit 4 and the output signal 4a becomes H level, the output level of the NOR circuit 6 becomes L, so the input terminal level of the inverter circuit 7 is lowered to L and the output signal 7a becomes H level.
The signal 7a remains at the H level for a time T when the capacitor 8 is charged with the positive potential 10 through the resistor 9 and the input terminal level of the inverter 7 reaches a predetermined value. Since the output signal 7a is input to the NOR circuit 6, even if the level of the signal 4a returns to L during the time T, or if a pulse is subsequently output from the frequency dividing circuit 4, the output signal 7a The state of does not change. signal 7a
When becomes H level, the reference pulse 12a is outputted as the output signal 11a of the NAND circuit only during the time T.

Since each part of the calibration circuit 5 is configured as described above, each time a pulse is output from the frequency dividing circuit 4, K ₂ pulse signals 11a are output from the NAND circuit 11, and this number K ₂ is It is adjusted by adjusting the time T using the variable resistor 9. 13 in FIG. 2 is the output signal 11a
A counting circuit that counts the number of pulses at 14 and outputs a counting signal 13a according to the counting result.
1 is an output circuit that amplifies the count signal 13, and 15 is a display that displays a signal corresponding to the count signal 13a output from the output circuit. Since the radiation dosimeter shown in FIG. 2 is configured as described above, if the number of pulses in the output signal 1a of the radiation detector is N ₁ and the frequency division ratio of the frequency dividing circuit 4 is K ₁ , then The number of pulses in the circumferential force signal 4a of the circumferential circuit is
Therefore, the number of pulses in the output signal 11a of the NAND circuit is ( _{N 1 /} K _{1 )}・
It becomes _K2 . Therefore, N ₁ · (K ₂ /K ₁ )=N ₃ pulses are counted by the counting circuit 13 and displayed on the display 15, which indicates the dose of radiation 2, but normally the detector The number N ₁ of pulses in the output signal 1a has an error with respect to the number N ₀ of pulses corresponding to the true irradiation dose of radiation 2 detected and erased 1. Therefore, in FIG. Therefore, the dosimeter is configured by adjusting K ₂ so that N ₃ =N ₀ . The frequency dividing circuit 4 is provided in order to reduce the pulse omission caused by the calibration circuit 5.

In FIG. 2, the calibration circuit 5 is adjusted as described above. Conventionally, the calibration of the dosimeter performed by this adjustment has been carried out using The radiation detector 1 of the radiation dosimeter is placed in a predetermined posture, the number of pulses is counted by the counting circuit 13 for a predetermined time, the radiation dose is displayed on the display 15, and the work of adjusting K ₂ with the resistor 9 is repeated. Since the final dose display on the display 15 is made to fall within a predetermined tolerance range, such a radiation dosimeter has a problem in that it takes a lot of effort to calibrate.
In particular, with this type of dosimeter, the calibration standards, including the form and intensity of the reference radiation source, the size and shape of the calibration location, the calibration position and orientation of the detector to be calibrated, etc., often change, and calibration work is required each time. Therefore, radiation dosimeters that require a long time for such calibration have the problem of not being able to respond immediately to changes in the calibration standard. Further, in FIG. 2, as mentioned above, one pulse is generated by the output signal 4a in the calibration circuit 5.
, even if a pulse is input to the calibration circuit 5 by the signal 4a, the output signal 7a remains unchanged during the time T.
does not change, so if the irradiation dose of the detector 1 is high, the pulse input to the NOR circuit 6 during the time T may be ignored. However, as mentioned above, the calibration of the dosimeter shown in Figure 2 is a one-point calibration performed using one reference radiation source, so even if the radiation dose is correctly calibrated, the radiation dose may be high. There is also the problem that the display accuracy deteriorates due to the neglect of the pulses input to the NOR circuit 6.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems with conventional radiation dosimeters and provide a radiation dosimeter that is easy to calibrate.

[Key points of the invention]

In order to achieve the above object, the present invention includes a radiation detector, a frequency dividing circuit that divides the output pulse signal of the radiation detector, and a frequency dividing circuit that counts the output pulse signal of the frequency dividing circuit and outputs a first count signal. a counting means for inputting a calibration count signal, a calibration coefficient recording means for rewriting the memory contents according to the signal and outputting a rewriting completion signal, and a first coefficient signal and the memory contents of the calibration coefficient recording means. a multiplication means for multiplying by the second count signal and outputting the result as a second count signal;
When a count signal is input, the recorded contents are rewritten according to this signal, when an output command signal is input, the stored contents are output as a data signal, and when a rewriting end signal is input, the stored contents are cleared. and a control means for outputting a reset signal and an output command signal to prevent the output pulse of the frequency dividing circuit from being guided to the counting means when a calibration start signal is input. By configuring the dosimeter in this way, the present invention can observe the data signal output from the data recording means, manually or automatically determine the configuration coefficient, and perform the calibration according to the calibration coefficient. The radiation dosimeter can be easily calibrated by inputting the calculated calibration coefficient signal into the calibration coefficient storage means.

[Embodiments of the invention]

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, 16 is a pulse form processing means consisting of the above-mentioned detector 1, amplifier 3, frequency dividing circuit 4, and component circuit 5, and 22 is an input port 17, a CPU 18,
A microcomputer includes a RAM 19, a ROM 20, and an output port 21 (hereinafter, the microcomputer may simply be referred to as a microcomputer); 23 is an input/output interface for the microcomputer 22;
24 is a light emitting diode, 25 is a phototransistor, 26 is a reed switch that operates in response to magnetism, and 28 is a reader having the functions described below. The display 15 and the light emitting diode 24 are both connected to the output port 2 via the interface 23.
1, and the phototransistor 25 and reed switch 26 are both connected to the input port 17 via the interface 23. 27 is a radiation dosimeter consisting of the above-mentioned parts except for the reader 28.

Next, the operation of the dosimeter shown in FIG. 1 will be explained. ROM
20 is stored in advance as an initial calibration coefficient, usually 1.0, and also stores the machine number of this radiation dosimeter. After setting the radiation detector 1 at a predetermined calibration position with respect to the reference radiation source,
When you turn on the power to this dosimeter, the CPU 18 first starts.
Read out the initial calibration coefficient from ROM19
Set to RAM19. Eventually, the radiation detector 1 detects the radiation 2, so a pulse signal 11a is output from the calibration circuit 5, and this signal is input to the input port 17 of the microcomputer. Then, CPU18
Count the number of pulses in the signal 11a, for example N ₃ , and multiply the counting result by the initial calibration coefficient stored in the RAM 19 to obtain the value N ₃ × 1.0 (in other words, the coefficient calibration value). ) RAM
19 and output to the output port 21 at the same time. When the count calibration value is output from the CPU 18 to the output port 21, the input/output interface 23 outputs a signal corresponding to this calibration value to the display 15, and the display therefore displays _N3 . This count value _N3 may be changed if the calibration is not performed accurately by the calibration circuit 5, or if the calibration circuit 5 is
If there is an omission in the number of pulses output by the detector 1, the value will be different from the pulse number N ₀ corresponding to the true irradiation dose of the detector 1 due to the radiation 2, as described above. That is, at this time, the value displayed on the display 15 shows a large measurement error.

Next, the reader 28 is brought close to the light emitting diode 24, the phototransistor 25, and the reed switch 26, which are arranged substantially in one row. Then the reader 28
The reed switch 26 is operated by a magnet (not shown) built into the reed switch 26, and a signal 26a resulting from this operation is sent to the interface 2 as a calibration start signal.
3 to the input port 17. CPU
18, when the signal 26a is input to the input port 17 via the interface 23, it is first output to the output port 2.
1, and this signal is input to the reset terminal 401 of the frequency divider circuit 4 via the interface 23. The frequency dividing circuit 4 is configured to stop outputting the pulse signal 4a when the reset signal 4b is input to the reset terminal 401. Stopping the output of the pulse signal 4a will be described later.
This is done in order to avoid adversely affecting the determination of the calibration coefficient _K3 by the CPU 18. CUP18
After outputting the reset signal 4b, it then outputs the dosimeter body number previously stored in the ROM 20 and the count calibration value _N3 stored in the RAM to the output port 21, and as a result, the light emitting diode 24 An optical signal indicating the aircraft number and the calibration value _N3 is output over time. After reading the light output of the light emitting diode 24, the reader 28 stores the light output in a built-in storage means in advance.
It is configured to calculate (N ₃ /N ₀ )=K ₃ using the count value N ₀ corresponding to the read aircraft number, and to input an optical signal according to the calculation result K ₃ to the phototransistor 25. has been done. When such an optical signal is input, the phototransistor 25 sends a calibration coefficient signal 25a corresponding to the signal to the interface 2.
3, and a signal corresponding to the resulting signal 25a is input from the interface 23 to the input port 17. Then, the CPU 18 first rewrites the memory contents of the RAM 19 so that the initial calibration coefficient 1.0 stored in the RAM 19 becomes _K3 , and then rewrites the counting calibration value N stored in the RAM 19 as described above. Clear ₃ ×1.0.

In Figure 1, each part operates as described above, and at this point, the calibration coefficient _K3 is written in the RAM 19, and the count calibration value as radiation dose data stored in this RAM has been cleared. Therefore, the displayed value on the display 15 is zero.
Then, the output of the peripheral force signal of the frequency dividing circuit 4 is still stopped. When the reader 28 is moved away, the signal 26a output from the reed switch returns to its normal state. Then, the microcomputer 22 detects this and stops outputting the reset signal 4b. As a result, the frequency divider circuit 4 no longer receives any signal input to the reset terminal 401, so it starts outputting the signal 4a again. Therefore, the signal 11a corresponding to the number N ₃ of pulses is output again from the calibration circuit 5, and in the microcomputer 22, the CPU 18 counts the number N ₃ of pulses and uses the counting result as a calibration coefficient stored in the RAM 19. Multiply K ₃ and obtain the counting calibration value
N ₃ and K ₃ are stored in the RAM 19 and simultaneously output to the output port 21 . As is clear from the above, N ₃ · K ₃ is N ₀ , so in this case the display 15 will display the correct dose, and as a result, the calibration of the dosimeter shown in Figure 1 has been completed. Become.

The radiation dosimeter 27 is calibrated as described above, and this calibration can be done by setting the reference radiation dose N ₀ in the reader 28 in advance. It is clear that the dosimeter 27 is easy to calibrate because it is not necessary to adjust the resistor 9 and observe the results of the adjustment.

In the embodiment of FIG. 1, the dosimeter is connected to the calibration circuit 5.
However, in the present invention, the calibration circuit 5 may not be provided, and in this case, the initial calibration coefficient value stored in advance in the ROM 20 will be _K2 , which need not be explained. In such a radiation dosimeter, the input pulses 4a are not omitted by the calibration circuit 5, so a dosimeter without the calibration circuit 5 is easy to calibrate and has good display accuracy.

Note that the ROM in each of the above-mentioned embodiments is
This is provided in case records are lost in the event of a power outage in RAM. Furthermore, in each of the above embodiments, the calibration coefficient _K3 was automatically calculated by the reader 28 and automatically inputted to the microcomputer 22, but in the present invention, such calculation and input operations are not required. may be performed manually.

Furthermore, although the reset signal is designed to stop the output pulse 4a of the frequency divider circuit 4, for example, a switch is provided on the output side of the frequency divider circuit 4 or the output side of the calibration circuit 5, and this switch is activated by the reset signal. It may be made non-conductive.

〔Effect of the invention〕

As described above, the present invention includes a radiation detector, a frequency dividing circuit that divides the output pulse signal of the radiation detector, and a frequency dividing circuit that counts the output pulse signal of the frequency dividing circuit and outputs a first count signal. a counting means for inputting a calibration coefficient signal; a calibration coefficient storage means for rewriting the stored content in accordance with the input signal and outputting a rewriting completion signal; and a first counting signal and the memory content of the calibration coefficient recording means. a multiplication means that multiplies the result by a second count signal and outputs the result as a second count signal, and when the second count signal is input, the memory contents are rewritten to the contents according to this signal, and when the output command signal is input, the memory contents are rewritten to the contents corresponding to this signal. data storage means that outputs the content as a data signal and clears the stored content when a rewriting end signal is input; and a data storage means that prevents the output pulse of the frequency dividing circuit from being guided to the counting means when a calibration start signal is input. The radiation dosimeter was configured to include a control means for outputting a reset signal and an output command signal. Therefore, the present invention includes a method for manually or automatically determining a calibration coefficient by observing a data signal output from a data storage means;
By inputting a calibration coefficient signal corresponding to this calibration coefficient into the calibration coefficient storage means, there is an effect that the radiation dosimeter can be easily calibrated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional radiation dosimeter, and FIG. 3 is an explanatory diagram of signal waveforms of the main parts in FIG. 1... Radiation detector, 1a, 11a... Pulse signal, 2... Radiation, 4b... Reset signal, 1
6... Pulse form processing means, 25a... Calibration coefficient signal, 26a... Calibration start signal, 27... Radiation dosimeter.

Claims (1)

[Claims] 1. A radiation detector that outputs a pulse signal according to incident radiation, a frequency dividing circuit that divides the output pulse signal of this radiation detector, and a frequency dividing circuit that counts the output pulse signal of this frequency dividing circuit and calculates the frequency according to the counting result. a counting means for outputting a first counting signal; and a calibration system for storing a calibration coefficient and rewriting the stored content in accordance with the content of the calibration coefficient signal each time the calibration coefficient signal is input, and outputting a rewriting completion signal. coefficient storage means;
a multiplier for multiplying the first count signal by the content stored in the calibration coefficient storage means and outputting the multiplication result as a second coefficient signal; a data storage means that outputs the stored content as a data signal when the output command signal is inputted, and clears the stored content when the rewriting end signal is inputted; control means for outputting a reset signal and the output command signal when a signal is input; the output pulse signal of the frequency dividing circuit is prevented from being guided to the counting means by the generation of the reset signal; A radiation dosimeter characterized in that the radiation dose is measured based on the radiation dose.