JPH036482A - Radiation measurement device and noise detection method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radiation measuring device, and particularly to a radiation measuring device that measures radiation using an ionization chamber.

[Conventional technology]

Numerous radiation measuring devices using ionization chambers are installed in atomic couplants, and an alarm is issued when radioactivity exceeding a predetermined value is detected.

In this radiation measurement device, when radiation (gamma rays) enters the ionization chamber, the inert gas filled therein is ionized, and a minute current flows through a conductor installed inside the ionization chamber. After this current is amplified by a preamplifier, it is input to a module such as a logarithmic dose rate meter, and the radiation dose is displayed and an alarm is issued. Since radiation is detected using a minute current, it is necessary to be careful about errors and false alarms caused by noise. Therefore, countermeasures are taken to minimize noise sources and shield the ionization chamber and preamplifier that are the detection parts. is taken. Also, as stated in Japanese Patent Application No. 60-216959,
Some devices have dual detection units to improve reliability.

[Problem to be solved by the invention]

The above-mentioned conventional technology is insufficient as a noise countermeasure because it merely takes care not to emit external noise and shields the detection unit from entering the noise. In other words, if noise enters the detection unit due to large external noise, the measured value of radiation changes significantly even though the true radiation dose has not changed, causing a problem in which a false alarm is issued. was there. Further, even if the detection section is duplicated, it is of no use as a countermeasure against this noise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation measuring device that can significantly reduce the influence of noise on measured values even when noise enters the detection section, and that can prevent false alarms from being output due to noise.

[Means to solve the problem]

The purpose of the above is to install a simulated load near the detector that has the same noise characteristics as the radiation detector inside the ionization chamber and does not respond to radiation at all, and to This is accomplished by providing a means for correcting the detector output and also controlling the alarm output according to the signal.

[Effect]

A radiation detector usually has electrical characteristics equivalent to a capacitor with a capacitance of several pF. Therefore, if a capacitor with this capacity is used as a simulated load, it will not react to radiation, but will have the same detection characteristics as the detector for noise. Therefore, it is possible to correct for the radiation, and when large noise is detected from the simulated load output, it is possible to prevent the output of a false alarm by not issuing an alarm output.

〔Example〕

Hereinafter, the present invention will be explained by examples. FIG. 1 shows an embodiment of the present invention, in which a radiation detection section 1 is comprised of a detector 4 and a simulated load 5 electrically equivalent to the detector 4. As shown in FIG. An ionization chamber is often used as the detector 4, but since this has characteristics electrically equivalent to a capacitor of several pF, a capacitor of the same capacity is used as the simulated load 5. The output signal from the detector 4 (in the case of an ionization chamber detector, a weak current signal of about 10-13 A) is sent to the cable 6.
A, the signal is amplified into a voltage signal of several volts by the preamplifier 7A in the amplifier section 2, and is input to the input section 8A of the module 3. On the other hand, the signal from the simulated load 5 is amplified by the preamplifier 7B in the amplifier section 2 via the cable 6B bundled together with the cable 6A, and is amplified by the preamplifier 7B in the amplifier section 2.
It is input to B.

In the module 3, the comparison section 10 compares the signal input from the detector 4 to the input section 8A and the signal input from the simulated load 5 to the input section 8B, and sends the difference signal 14 to the calculation section 9. Furthermore, when the signal from the simulated load 5 is above a certain level, the measured value switching command 13 is turned on and output to the calculation section 9. The calculation unit 9 calculates the radiation measurement value from the difference signal 14 while the measurement value switching command 13 is on, and uses the output signal of the detector 4 to the input unit 8A as it is when it is off. Calculate the measured value of radiation. The radiation measurement value calculated in this manner is displayed on the display section 11 and outputted to the outside as a voltage 12.

According to this embodiment, when external noise enters the detection section 1, the simulated load 5 and the detector 4 are equally affected, so if the comparison section 1o of the module 3 generates the difference signal 14, this noise will be detected. A detection signal in which only the components are canceled can be obtained. In addition, in the case of a weak current signal from an ionization chamber detector,
Although an erroneous signal of about 10-''A can easily be generated due to vibration or bending of the cable between the detection section 1 and the amplification section 2, it is recommended that the cables 6A and 6B be housed in the same cable or laid very close together. By doing so, these erroneous signals can be canceled out.Also, in the configuration shown in Fig.
It is also possible to hold the measured value to be displayed and output when the signal exceeds a certain level, thereby preventing the output of an erroneous signal.

Moreover, the same effect can be obtained even if the simulated load 5 is provided near the outside of the detection unit 1.

FIG. 2 shows a second embodiment of the present invention, in which a circuit for removing the influence of noise and the like is provided in the amplifier section 2, and other parts are the same as in FIG. 1. The signals from the detector 4 and the simulated load 5 are sent to the preamplifiers 7A and 7B as in FIG.
is amplified by

This amplified signal is a difference signal obtained by subtracting the signal from the simulated load 5 from the signal from the detector 4 by a differential amplifier 16 provided in the amplifying section 2, that is, a signal from which error components such as noise are removed. After being converted into , it is output to module 3. Therefore, correct measured values containing no erroneous signals are displayed and output. Note that in this case, the input section 8B and the comparison section 10 in the module 3 are unnecessary.

FIG. 3 shows an embodiment in which a comparator 15 is provided in the amplifier section 2 and an alarm 20 is output when an erroneous signal occurs. The signals from the detector 4 and the simulated load 5 are as in the case of FIG.
It is amplified by preamplifiers 7A and 7B. A comparator 15 provided in the amplifier section 2 compares the signal of the amplifier 7B with a certain level, and when the signal of the amplifier 7B exceeds the certain level, the signal of the amplifier 7B is
An alarm 20 is output indicating that the signal output from A to the module 3 is an erroneous signal. Furthermore, in the module 3, the signal from the detector 4 is converted into a radiation dose (this module also has the comparator 10 in FIG. 1 removed), and outputs an alarm 19 when the radiation dose exceeds a certain level. . When the alarm 20 indicating an erroneous signal is on, the AND circuit 18 is closed via the NOT circuit 17 which performs on/off reversal, and the alarm 19 is determined to be an error and is not output. If there is no noise and the alarm 20 is off, the AND circuit 18 is in an open state, and the alarm 19 is output as an alarm 21 indicating the presence of radiation.

FIG. 4 shows a modification of the present invention, which has the same operation and configuration as FIG. When the preamplifier 7A that amplifies the signal is damaged, radiation monitoring can be continued using the amplifier 7B by switching the four switches in the direction of the arrow in the figure.

That is, when the preamplifier 7A fails, the signal from the detector 4 passes through the cable 6A, passes from the switch 22A to the switch 22B, and is input to the amplifier 7B where it is amplified. The output of amplifier 7B is output from switch 22D to switch 22.
The radiation is sent to module 3 via G, where it is converted into a radiation dose and output for display.

FIG. 5 shows an application example of the present invention, and shows an erroneous signal detection mechanism when inputting and outputting signals between two devices. When outputting a large number of signals 26 from the device 24 to the device 25, a simulated load 27 is provided in the output device 24, and the signals from the simulated load 27 are sent to the comparator 28 in the input device 25.
Enter. The comparator 28 performs a comparison with the ground level, and outputs an error signal detection alarm 29 if the difference is greater than a certain level. As described above, two devices 24. 25
When inputting and outputting signals between devices, it is possible to prevent the transmission and reception of erroneous signals due to noise, etc., or to output an alarm.

〔Effect of the invention〕

According to the present invention, noise components entering the detector can be significantly reduced, making it possible to accurately measure radiation doses, and
This has the effect of preventing the output of false alarms due to noise.

[Brief explanation of drawings]

1 to 3 are views showing embodiments of the present invention, FIG. 4 is a view showing a modified example of the present invention, and FIG. 5 is a view showing an applied example of the present invention. 3... Module, 4... Detector, 5... Simulated load, 6A, 6B... Cable, 7A, 7B... Preamplifier, 9... Arithmetic unit, 10... Comparison Part 12...
- Measured value output, 13... Measured value switching command, 14...
Difference signal, 16... Differential amplifier, 17... Not circuit, 18... AND circuit, 20... Alarm, 22A~2
2D...signal changeover switch, 24...output side device,
z5... Input side device, 27... Simulated load, 28...
・Comparator, 29...False signal detection alarm.

Claims (1)

[Claims] 1. In a radiation measuring device that calculates and outputs a radiation measurement value after amplifying the output signal of a radiation detector with a detector preamplifier, a radiation measuring device arranged near the radiation detector and connected to the detector A load having electrically equivalent characteristics, a load preamplifier for amplifying the output signal of the load, and correcting the radiation measurement value or changing the output according to the output value of the load preamplifier. A radiation measuring device characterized by being provided with auxiliary means for performing. 2. The radiation measuring device according to claim 1, wherein the load is a capacitor adjusted to have a capacitance equal to the capacitance of the radiation detector. 3. The auxiliary means outputs the detector preamplifier output,
3. The radiation measuring device according to claim 1, wherein the output is replaced by a value obtained by subtracting the load preamplifier output from the output. 4. The auxiliary means controls so as not to output the calculated radiation measurement value or an alarm based on the measurement value when the output of the load preamplifier exceeds a predetermined value. The radiation measuring device according to claim 1 or 2. 5. Claim 1 or 2 further comprising a switching means for switching the radiation detector output to be amplified by the load preamplifier instead of the detector preamplifier.
The radiation measuring device described. 6. Provide a load with electrically equivalent characteristics to the output circuit on the signal output side device, and output an ON signal to the input side device when the level of the signal from the load exceeds the ground potential by a predetermined value. 1. A noise detection method comprising: a comparison means; and when an output of the comparison means is on, it is determined that a signal cannot be normally transferred from the output side device to the input side device.