JP2003227875A - Noise reduction device for radiation measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an erroneous signal from being generated due to a noise and to prevent an erroneous warning from being generated by preventing the noise from creeping into a field panel from an outside-of-panel signal cable in a detector. <P>SOLUTION: A radiation detector 2 and a guide tube 3 with the built-in signal cable 4 are attached to a partition wall 1 in a building, and the signal cable 4 is connected to an entrance-side cable in a ferrite core 9 through a pull box 5 attached to the partition wall 1 and a conduit tube 6. The ferrite core 9 is housed inside a ferrite core box 8 attached to the inner surface of the field panel 7. An exit-side cable in the ferrite core 9 is connected to a signal amplifier 10, and the signal amplifier 10 is connected to a signal processor 11. The signal amplifier 10 and the signal processor 11 are connected to a low-voltage power supply 13, and the power supply 13 is connected to a noise cutoff transformer 17. The transformer 17 is connected to a no-fuse breaker 20, and the no-fuse breaker 20 is connected to a terminal base 21. The terminal base 21 and the no-fuse breaker 20 are housed inside a metal shielding box 28. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reducing apparatus for a radiation measuring apparatus which prevents generation of false signals and false alarms due to noise from the radiation detector side and the power source side in the panel.

[0002]

2. Description of the Related Art A radiation measuring apparatus has important functions such as measuring radiation and issuing an alarm. On the other hand, in the building where the radiation measuring apparatus is installed, a high-frequency noise generating device in the frequency band of the high-gain measuring circuit system such as an inverter motor is installed, and countermeasures against it are important.

A conventional general noise measuring apparatus for radiation measurement will be described with reference to FIG. In FIG. 3, reference numeral 1 is a partition wall of a building, and an opening end of a guide pipe 3 which penetrates the partition wall 1 and houses a radiation detector 2 is fixed to the partition wall 1. A signal cable 4 is connected to and led out from the radiation detector 2. A pull box 5 is attached to the partition wall 1 so as to cover the open end of the guide pipe 3.

To the pull box 5, one end of a conduit tube 6 for guiding and guiding the signal cable 4 is connected. The other end of the conduit 6 is connected to a board, for example, a ferrite core box 8 provided on the field board 7. A ferrite core 9 is housed in the ferrite core box 8, and the other end of the signal cable 4 is connected to the cable on the inlet side of the ferrite core 9.

The exit side cable of the ferrite core 9 is connected to the signal amplifier 10 installed in the field board 7. The output side of the signal amplifier 10 is connected to the signal processor 11,
An optical cable 12 is connected to the output side of 11.

The signal amplifier 10 and the signal processor 11 are low voltage power supplies.
The low-voltage power supply 13 is connected to the low-voltage power source 13 via the dedicated grounding cable terminal plate 15 by the dedicated grounding cable 14. The low-voltage power supply 13 is a noise cut transformer (hereinafter NC
T) It is connected to the NCT 17 via the cable 16.

The NCT 17 is generally grounded by a general ground cable 19 via a general ground terminal plate 18, and N
No-fuse breaker 20 as a device in the CT17 primary side panel
A terminal block 21 is provided, and the terminal block 21 is connected to an AC 100V power source outside the site panel 7.

As described above, the conventional noise reducing apparatus for radiation measuring apparatus basically adopts the double shield method, and the guide pipe 3, the pull box 5, the electric wire tube 6, and the site panel 7 are outside electrical equipment. It is a shield.

The radiation detector 2, the signal amplifier 10, the signal processor 11, the low voltage power source 13 and the like are electrically insulated from the site panel 7 and the like, and the low voltage power source 13 is electrically connected to the primary side and the secondary side by the NCT 17. It is insulated from noise. The equipment inside the double shield is grounded with a dedicated ground.

The guide pipe 3, the pull box 5, the conduit tube 6 and the site board 7 are electrically connected, and external noise is released from the general ground 19 of the site board 7 to the building ground.
The inside of the double shield (the signal amplifier 10, the signal processor 11, the low-voltage power supply 13) prevents noise from entering the high gain circuit.

External noise that has entered from the outside electrical shield is wound around the signal cable 4 around the ferrite core 9 in the ferrite core box 8 to reduce the noise. The signal from the radiation detector 2 is amplified by the signal amplifier 10, processed by the signal processor 11 at the next stage, converted into an optical signal, and transmitted to the control panel (not shown) by the optical cable 12 to have a predetermined level. If exceeded, an alarm will be issued. As a noise intrusion to the field panel 7 from other than the signal cable 4, the low voltage power supply 13
There is noise ingress from the side, where NCT17 is used.

[0012]

In order to improve the noise shielding ability of the signal cable 4 in the conventional noise reducing device of the radiation measuring apparatus, the signal cable 4 is a double or triple shielded cable and is quite thick. Are using. Therefore, in order to secure the required number of turns with a predetermined radius of curvature of the cable, it is necessary to enlarge the ferrite core box 8.

If there is no place for installing the ferrite core box 8 around the site panel 7, a method of attaching a worm type ferrite used in the AC cable of a personal computer can be considered, but the efficiency is poor. However, the use of ferrite is difficult.

Further, as the noise intrusion into the field panel 7 from other than the signal cable 4, there is noise intrusion from the AC100V power source side, but generally NCT17 or a filter is installed.

However, when the size of the site panel 7 is limited, the NCT 17 as the internal device on the primary side panel in the preceding stage
The FB20, the terminal block 21, etc. are close to the exposed part and the high gain circuit, and the noise in the preceding stage of the NCT17 enters the high gain circuit (signal amplifier 10), which causes a false signal and false alarm. is there.

The present invention has been made to solve the above problems, and reduces noise from the radiation detector side and noise from the power source side to prevent generation of false signals and false alarms due to noise. It is an object of the present invention to provide a noise reduction device for a radiation measurement device that can do the above.

[0017]

The invention according to claim 1 is
A guide pipe having a built-in radiation detector, a conduit for leading out the signal cable of the radiation detector, a board for fixing the other end of the conduit, a ferrite core box fixed on the inner surface of the board, and the ferrite A ferrite core having an inlet-side cable that is housed in a core box and connected to a signal cable in the conduit, a signal amplifier, a signal processor, and an optical cable that are sequentially connected in series to the outlet-side cable of the ferrite core; and the signal amplifier, A low-voltage power supply connected to the signal processor, a general ground connected to the low-voltage power supply, a noise cut transformer connected to the general ground, and a device in the primary side panel connected to the noise cut transformer. Is provided.

According to the first aspect of the present invention, the signal cable from the outside of the board and the signal cable wound around the ferrite core are housed in the metal ferrite core box. Does not affect inside. Also, by electrically connecting the ferrite core box to the board, noise in the previous stage of the ferrite core can be released to the board, and the sneak into the high gain circuit system is reduced,
It is possible to prevent generation of false signals and false alarms due to noise.

The invention according to claim 2 is characterized in that the inlet side cable wound around the ferrite core is provided with a capacitor and is grounded. According to the invention of claim 2, the connector for connecting the inlet side and the outlet side of the ferrite core in the ferrite core box is insulated by an insulating plate, and the inlet side is connected at high frequency via a capacitor. ing. The high-frequency noise voltage in the preceding stage of the ferrite core is released to the ground via the capacitor and helps the noise reduction effect of the ferrite. The noise in the preceding stage of the ferrite can be released to the board, the sneak into the high gain circuit system can be reduced, and the generation of false signals and false alarms due to noise can be prevented.

The invention according to claim 3 is characterized in that the signal cable end in the conduit and the inlet side cable around the ferrite core are connected by a cable size down conversion connector.

According to the third aspect of the present invention, the connector on the ferrite core inlet side is a cable size down conversion connector, which can convert a thick signal cable into a thin signal cable. Since the signal cable wound around the ferrite core can be made thin, it can be finished compactly even if the radius of curvature is small and the required number of turns is secured, and it is possible to rationalize the installation space and manufacture a compact board.

The invention according to claim 4 is characterized in that the device in the primary side panel of the noise cup transformer is housed in a metal shielding box. According to the invention of claim 4, the device inside the panel on the primary side of the noise cut transformer is housed in the metal shielding box to prevent the sneaking of noise, reduce the sneaking into the high gain circuit system, and cause an error due to noise. Signals and false alarms can be prevented.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a noise reducing apparatus for a radiation measuring apparatus according to the present invention will be described with reference to FIGS. 1 and 2. 1 is a vertical cross-sectional view showing a partial block diagram of the configuration of the present embodiment, and FIG. 2 is an enlarged partial cross-sectional view of a portion A in FIG. The same parts as those in No. 3 will be described with the same reference numerals.

The difference between this embodiment and the conventional example is shown in FIG.
As shown in FIG. 5, the ferrite core box 8 is attached to the inner surface of the field board 7, and the inlet side cable 9a of the ferrite core 9 in the ferrite core box 8 and the terminal portion of the signal cable 4 in the conduit 6 are downsized conversion connectors. It is connected by 22. This size down conversion connector
22 is fixed by penetrating the insulating plate 23, and the insulating plate 23 is fixed by the fixing plate 24.
The fixing plate 24 is fixed to the inner surface of the ferrite core box 8.

A capacitor 25 is connected between the size-down conversion connector 22 and the fixed plate 24. The outlet side cable 9b of the ferrite core 9 is connected to the connection connector 26, and the connection connector 26 is fixed by penetrating an insulating plate 27 provided at the end of the ferrite core box 8.

Further, as shown in FIG.
The FB 20 and the terminal block 21 are housed in the metal shield box 28, and the metal shield box 28 and the NCT 17 are connected by the flexible metal tube 29.

That is, in the present embodiment, the radiation detector 2 and the signal cable 4 are housed in the guide pipe 3 up to the partition wall 1 of the building and shielded from external noise. The guide pipe 3 is connected to the pull box 5 at a position protruding from the partition wall 1 so as to be in electrical contact with the pull box 5. The signal cable 4 is housed in a conduit 6 connected between the pull box 5 and the site panel 7 in an electrically contacting manner, and shielded from external electrical noise.

The noise penetrating the radiation detector 2 or the signal cable 4 through the shield flows as a noise current in the outer cover of the signal cable (coaxial cable) 4. If there is no ferrite core 9 or the like, this current will enter the high gain signal amplifier circuit and cause an erroneous signal. In the conventional example,
There is a sufficient space, and a ferrite core box 8 is provided outside the site panel 7 to prevent noise from entering.

The present embodiment is intended for the case where there is not enough space outside the site panel 7. Therefore, the signal cable 4 contaminated by noise makes an area of the ferrite core box 8 electrically shielded by a metal plate at the entrance of the site panel 7 in order to avoid swaying noise in the site panel 7. .

The signal cable 4 is connected to the narrow inlet side cable 9a through the size-down conversion connector 22 electrically insulated from the field panel 7, and is wound around the ferrite core 9 a predetermined number of times with a small radius of curvature. It has a compact shape. Further, the whole is surrounded by a ferrite core box 8 made of a metal plate to prevent noise from leaking into the field board 7.

Since the inductance of the signal cable wound around the ferrite core 9 is as large as about 1 mH and becomes a large impedance against high frequency noise, and a voltage drop occurs, the high frequency noise potential of the signal cable 4 in the preceding stage of the ferrite core 9 is Get higher In order to quickly pass this noise to the ground, the outside portion of the connector on the inlet side is grounded to the field panel 7 with the capacitor 25 for high frequency noise bypass.

Therefore, the external noise is
With a very compact ferrite core box 8,
Noise is efficiently reduced without radiating high frequency noise into the site panel 7. Similar to the conventional example, the signal is amplified by the signal amplifier 10 in the field panel 7, processed by the signal processor 11 at the next stage and converted into an optical signal, and transmitted from the optical cable 12 to the control panel (not shown). An alarm is issued when the level exceeds a predetermined level.

NFB on the primary side of the noise cut transformer 17
The terminal block 21 and the terminal block 21 are electrically shielded so as not to radiate noise into the site panel 7. In the present embodiment, the device inside the panel on the primary side of the noise cup transformer 17 is housed in the metal shielding box 28 to prevent the sneak of noise, reduce the sneak into the high gain circuit system, and prevent the false signal due to the noise. It is possible to prevent the occurrence of false alarms.

[0034]

According to the present invention, the end portion of the signal cable for the detector from the board and the signal cable wound around the ferrite core are housed in the metal ferrite core box, so that the noise in the preceding stage of the ferrite is stored in the board. Can be prevented from entering. In addition, by connecting the metal ferrite core box to the inner surface of the panel, noise in the preceding stage of the ferrite can be released to the panel, the sneaking into the high gain circuit system is reduced, and false signals and false alarms due to noise are generated. Can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a part of a block for explaining an embodiment of a noise reducing apparatus for a radiation measuring apparatus according to the present invention.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a vertical cross-sectional view showing a part of a block for explaining a conventional noise reducing apparatus for a radiation measuring apparatus.

[Explanation of symbols]

1 ... Partition wall, 2 ... Radiation detector, 3 ... Guide pipe, 4
… Signal cable, 5… Pull box, 6… Conduit, 7…
Site panel, 8 ... Ferrite core box, 9 ... Ferrite core, 9a ... Inlet side cable, 9b ... Outlet side cable,
10 ... Signal amplifier, 11 ... Signal processor, 12 ... Optical cable, 13
… Low voltage power supply, 14… Dedicated ground cable, 15… Dedicated ground cable terminal plate, 16… NCT cable, 17… Noise cut transformer (NCT), 18… General ground terminal plate, 19… General ground cable, 20… No fuse Breaker (NFB), 21
… Terminal block, 22… Size down conversion connector, 23… Insulation plate, 24… Fixed plate, 25… Capacitor, 26… Connection connector, 27… Insulation plate, 28… Metal shielding box, 29… Flexible metal tube.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naotaka Oda             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F term (reference) 2G088 EE21 FF01 GG00 JJ33 KK20                       KK40 LL11

Claims (4)

[Claims] 1. A guide pipe having a built-in radiation detector, a conduit for leading out a signal cable of the radiation detector, a board for fixing the other end of the conduit, and a ferrite core fixed to the inner surface of the board. A box, a ferrite core having an inlet side cable that is housed in the ferrite core box and connected to the signal cable in the conduit tube, and a signal amplifier, a signal processor, and an optical cable that are sequentially connected in series to the outlet side cable of the ferrite core. A low-voltage power supply connected to the signal amplifier and the signal processor, a general ground connected to the low-voltage power supply, a noise cut transformer connected to the general ground, and a primary connected to the noise cut transformer A noise reducing apparatus for a radiation measuring apparatus, comprising: a device inside a side panel. 2. The noise reducing apparatus for a radiation measuring apparatus according to claim 1, wherein the inlet side cable wound around the ferrite core is provided with a capacitor and is grounded. 3. The radiation measuring apparatus according to claim 1, wherein the signal cable end in the conduit and the inlet side cable around the ferrite core are connected by a cable size down conversion connector. Noise reduction device. 4. The noise reducing apparatus for a radiation measuring apparatus according to claim 1, wherein the device inside the primary side panel of the noise cup transformer is housed in a metal shielding box.