JPS649782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection circuit that uses earth/open air as an interface condition.

2. Description of the Related Art Conventionally, a monitoring device including a detection circuit and an information processing unit has been provided in order to quickly and accurately automatically detect an alarm signal given from a monitored device and quickly deal with the alarm from the monitored device. A conventional failure check for a detection circuit that detects an alarm signal from a monitored device uses a switch installed in the detection circuit to forcibly set the detection circuit to the same state as the alarm generated from the monitored device. We are checking to see if it works.

However, there are two types of failures in the detection circuit: a case where an alarm is not recognized as an alarm even if an alarm is input from the monitored device, and a case where it is recognized as an alarm even when no alarm is input. In conventional detection circuit checks, the detection circuit is checked to see if it operates normally by setting it in the same state as the alarm generated by the monitored device, so an alarm can be detected even without an alarm input from the monitored device. The disadvantage is that there is no check for recognized failures.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a detection circuit that can accurately check the detection circuit.

The detection circuit of the present invention includes a conversion circuit that converts alarm information to a TTL level, an information sending unit that sends the output of this conversion circuit to an information processing unit every time an information sending request is received, and a detection circuit that forcibly controls the conversion circuit. means for generating a mode switching signal that alternates between a first state and a second state each time the information sending request is received, in a detection circuit having an operation test switch that sets the state to the same state as when the alarm information is present; and when the mode switching signal is in the first state while the operation test switch is operating, the connection of the signal by the operation test switch to the conversion circuit is forcibly interrupted, and the alarm information is input. and means for forcibly prohibiting all.

Next, a detailed description will be given with reference to the drawings.

FIG. 1 is a block diagram showing a conventional detection circuit. In the figure, alarm signals from the monitored device are input to the conversion circuit 1 via alarm signal lines 8, 9, 10 and 11. In the conversion circuit 1, the alarm signal from the monitored device is converted to a TTL level and then input to the selection circuit 2. The unit selection circuit 4 determines whether the address information sent from the information processing section via the address signal line 5 specifies this detection circuit, and sends this determination result to the selection circuit via the unit selection signal line 7. Enter 2. The selection circuit 2 takes in the monitored device alarm sent from the conversion circuit 1, and when this detection circuit is selected by the selection signal sent via the unit selection signal line 7, it outputs the monitored device alarm as data. Output to signal line 3. Further, the switch 6 is connected to the conversion circuit 1, and when the switch 6 is turned on (conducting), the conversion circuit 1
The monitored device enters the same state as when the alarm was sent, and all alarm occurrence information is output to the selection circuit 2.

Conventionally, when checking a detection circuit, the information processing section determines that the detection circuit is normal when all information about the monitored device sent via the data signal line 3 indicates that an alarm has occurred. Therefore, even when the detection circuit is malfunctioning and continues to generate an alarm, the information processing section has the disadvantage that it may erroneously determine that the detection circuit is normal.

FIG. 2 is a circuit diagram showing one embodiment of the present invention. The same parts as in FIG. 1 are indicated by the same reference numerals. The unit selection signal line 7 is connected to the selection circuit 2 as in the conventional case, and is further connected to the mode switching circuit 12. The mode switching circuit 12 switches the output signal ON/OFF every time the unit selection signal designates this detection circuit. The output signal of the mode switching circuit 12 is input to the AND circuit 13 via the mode switching signal line 15. In addition, the switch 6 is connected to the conversion circuit 1 as before,
Furthermore, it is connected to an AND circuit 13. In the AND circuit 13, the input switch 6 is ON (conducting)
And only when the content of the mode switching signal line 15 is ON, the output is turned ON (ground air). The output of the AND circuit 13 is connected to the relay 14, and operates when the output of the AND circuit 13 is ON (ground air).
Relay contacts 16, 17, 18 and 19 of relay 14 connect to alarm signal lines 8, 9, 10 and 11.
between the two, and when the relay 14 operates, the contact is
Turn it OFF (open). In addition, the relay contact 20 of the relay 14 is located between the signal line connecting the switch 6 and the conversion circuit 1, and when the relay 14 operates, the contact is closed.
Turn it OFF (open).

Switch 6 for detection circuit unit check
When set to ON, the output of the mode switching circuit 12 will turn ON/OFF each time this unit is selected from the information processing section.
Therefore, the relay 14 repeatedly operates and releases.
When the relay 14 operates, the relay contact 20 is opened, and the forced alarm generation state of the conversion circuit 1 is released. In addition, relay contacts 16, 17, 18 and 19 are opened, and the conversion circuit 1 enters a monitored device alarm state regardless of the monitored device.

Also, when the relay 14 is not operating, the conversion circuit 1
Now, a monitored device alarm has been sent. As a result of the above, when a detection circuit unit is selected by the information processing section at the time of a detection circuit check, repeated information of all alarm generation states and all alarm non-alarm states is input to the information processing section. The information processing section determines that the detection circuit unit is normal when the information input from the detection circuit unit is a repetition of all alarm occurrence states and all alarm non-occurrence states, and otherwise determines it to be abnormal.

According to the present invention, there is an advantage that the information processing unit can detect a failure in the detection circuit that causes an alarm to occur at all times and a failure that does not cause an alarm to occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional detection circuit, and FIG. 2 is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Conversion circuit, 2... Selection circuit, 3... Data signal line, 4... Unit selection circuit, 5... Address signal line, 6... Switch, 7... Unit selection signal line,
8, 9, 10, 11... Alarm signal line, 12... Mode switching circuit, 13... AND circuit, 14... Relay, 15... Mode switching signal line, 16, 17, 1
8, 19, 20...Relay contacts.

Claims (1)

[Claims] 1. A conversion circuit that converts alarm information to a TTL level; an information sending section that sends the output of this conversion circuit to an information processing section every time an information sending request is received;
and an operation test switch that forces the conversion circuit to be in the same state as when the alarm information is present, and the detection circuit alternates between the first state and the second state each time the information transmission request is received. means for generating a mode switching signal; and when the mode switching signal is in the first state while the operation test switch is operating, forcibly interrupting the connection of the signal by the operation test switch to the conversion circuit. The detection circuit further comprises means for forcibly prohibiting input of all of the alarm information.