JPS59100636A - Detector for disconnection of dc signal cable - 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 The present invention relates to a DC signal cable disconnection detection device that detects disconnection of a DC signal cable led out from a signal detection end without affecting a signal detection system.

In a process instrumentation system, there are many connections between the signal detection terminal that detects process quantities such as pressure and flow rate, or the energy of radiation, etc., and the instruments on the central monitoring panel and C signal cables, which ensure the safety of the equipment. Detection of disconnections in signal cables is carried out from this perspective.

By the way, conventional means for detecting disconnections in signal cables involves disconnecting the connector at the end of the signal cable and checking for disconnections by conducting an energization test when the process is stopped, such as during a pre-start inspection of equipment. Another method for detecting disconnection was to multiplex the A signal detection systems, disconnect the connectors of each system one by one, and check for disconnections using an energization test.

However, the disconnection detection means as described above has the disadvantage that the operation is complicated and time-consuming because it requires the removal and insertion of the connector cover. Additionally, there are problems that cannot be checked when the process is running. Furthermore, when there are a large number of connectors, there is a possibility that the connectors may be inserted incorrectly after testing, and countermeasures such as changing the shape of the connectors individually are required.

The present invention has been made in view of the above-mentioned circumstances, and it eliminates the need to disconnect the connector of the DC signal cable from the signal detection end, etc., and can be used regularly or periodically without affecting the detection function of the signal detection section. It is an object of the present invention to provide a disconnection detection device for a DC signal cable that performs a disconnection check.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. First, FIG. 1 is a diagram showing an outline of the apparatus, and 11 is a signal detection end 11 for detecting a process amount or radiation energy. This signal detection end 11
A DC signal detection section 14 is connected to the 10,000 output end 12a via a DC signal cable 13. This blood flow signal detection section 14 detects a DC signal output from the signal detection end 11, and has an operational amplifier J4a and a capacitor 14b.
and resistor 14 c f < time constant C when connected in parallel
It constitutes an integrating circuit with R. Reference numeral 15 denotes a current/rush generator that provides a disconnection check signal to the DC signal cable 13 side and a judgment reference signal to the subsequent logic judgment circuit 16. 17 is a DC power supply, and the DC voltage output from this power supply 17 is supplied to the signal detection end 11 via a power supply cable 18. 19 is a current pulse generator 15
DC signal cable 13. This is a current pulse detector that detects the current noise input through the internal wiring of the signal detection socket 1 and the power supply cable 18, and the pulse detected here is sent as is or after waveform shaping to the logic judgment circuit. 16.

The logic judgment circuit 16 logically judges the judgment criterion No. 46 from the current pulse generator 15 and the signal from the current pulse detector 19 and outputs a judgment signal as to whether or not there is a disconnection. 20
Terminals a and 20b are terminals for signal detection and judgment.

FIG. 2 shows a specific example in which the apparatus shown in FIG. 1 is applied to, for example, a radiation energy signal detection system. First, as the signal detection end 11, for example, a compensation type ionization chamber is used, and this includes positive,
A high negative voltage is supplied. Therefore, the detection end 11 has three output terminals 12m and 12b-1°12.
b-2, and in addition to the DC signal cable 13, power supply cables 18-J and 1B-2 are connected to the two output ends 12b-1 and 12b-2. . These cables 13.18-1.18. -2
A coaxial cable is used for this. A positive high voltage DC power source 17-1 is connected to the power supply cable 18-1 side, and a negative high voltage DC power source 17-2 is connected to the other cable 18-2 side. . Similarly, each cable 1B-1.

Current pulse detectors 19-1 and 19-2 are connected to 18-2 via capacitors C1 and C2f. The logic judgment circuit 16 includes NAND circuits 5-16th-1, 16a-2 and a flip-flop 16.
b-1, 16b-2, a delay element 16c, AND circuits 16d-1, 16d-2, and an OR circuit 16e.

Next, the operation of the apparatus shown in FIG. 2 constructed as above will be explained. The DC signal detected by the signal detection end 11 is sent to the DC signal detection unit 14 via the DC signal cable 13. This blood flow signal detection unit 14 detects the DC signal from the signal detection end 11, and sends it as appropriate. Convert to a signal (for example, A-
After D conversion, etc.), the signal is sent to a signal processing system, etc. (not shown).

When the DC signal is detected or not detected, the current pulse generator 15 regularly or periodically generates a polar current pulse P1 having a pulse width Pw and a square wave having a pulse width T. Pulse judgment reference signal P2
At this time, the current All sous 1 is applied to the DC signal cable IBK, but the DC signal detection unit 14
Ha1 flowing No'Rus P1's Al Rus @pw! D4 dog! 6
- Since the DC signal is detected with the time constant CR, the DC signal can be detected without being affected by the current/gusus P1. On the other hand, if there is no disconnection accident in the cable 13, the current applied to the DC signal cable 13 enters the ionization box, and passes through the interelectrode capacitance of this ionization box to the power supply cable. 18-1.

It is returned by 18-2. Here, the current pulse detector 19-1, 19-2 is connected to the cable 1B-1, 18-
After detecting the current pulse P fed back by 2 and changing the detected pulse as it is or changing it into an appropriate signal, the NAND circuit 16a-1, 1 of the logic judgment circuit 16
Supply to 6h-2. This NAND circuit 16a-1, 1
6h-2 normally resets the 7-lip frogs 16b-1 and 16b-2 when the current pulse P1 does not return.
When returned, the reset state is released. Therefore, in order to cancel the reset, the judgment reference signal P
2 passes through the delay element 16c to the flip-flop 16b-
1, 16b-2 as a set signal, the same flip-flop J6b-2, 16b-2 outputs '1'.
``'' logic signal is output and AND circuits 16d-1, 16d-
2 is input. At this time, AND circuit 16d-1,1
If the judgment reference signal is input to the universal terminal of 6d-2, a judgment signal indicating that there is no cable breakage is output when the conditions of the AND circuits 16d-1 and 16d-2 are satisfied.

In the above embodiment, a current pulse is used as a signal for checking for disconnection, but a voltage pulse may also be used. It goes without saying that the method is not limited to bipolar current pulses.

As described in detail above, according to the present invention, it is possible to check whether or not a DC signal cable or a power supply cable is disconnected while a DC signal is being detected without removing the DC signal cable from the signal detection end. Moreover, without automatically sending out current pulses on a regular or periodic basis,
You can easily check for disconnections without any human intervention.
Furthermore, it is possible to provide a blood flow signal cable disconnection detection device that can check for disconnections without affecting the function of the signal detection system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the device of the present invention, and FIG. 2 is a specific configuration diagram in which the device of the present invention is applied to a radiation energy detection thread. 11... Signal detector, 13... Blood flow signal cable,
14... DC signal detection unit, 15... Current/arm pulse generator, 16... Logic judgment circuit, 17... DC power supply,
18...Power supply cable, 19...Current/main pulse detector. Applicant's agent Patent attorney Takehiko Suzue 9-21

Claims (1)

[Claims] In a signal detection system in which a DC signal detecting section detects a DC signal sent from a signal detection end side via a current signal cable, a judgment checking pulse having a pulse width Pw is applied to the DC signal cable. At the same time, a pulse generator outputs a judgment reference signal with a pulse width T'f: and an internal circuit of the pulse generator, the DC signal cable, and the signal detection end? a pulse detector that detects the presence or absence of all four pulses (for the judgment check inputted via A disconnection detection device for a DC signal cable, comprising a logical judgment circuit for determining whether or not the signal cable is disconnected.