JP4035781B2 - Current input module - Google Patents

Description

The present invention relates to a current input module that receives a current signal generated from a sensor or the like and supplies it to a host device such as a process control device.
More specifically, the present invention relates to a current input module suitable for a duplex configuration.

  FIG. 4 is a block diagram showing an example of a conventional current input module. In the figure, reference numerals 1 and 2 denote dual current input modules having the same configuration. SS is a current signal source such as a sensor, SW1 and SW2 are FET switching circuits, R1 and R2 are current detection resistors, D1 and D2 are diodes, AD1 and AD2 are A / D conversion circuits, and COM1 and COM2 are control devices. is there.

  As shown in the figure, the current detection resistors R1 and R2 are connected to the current signal source SS via the switch circuits SW1 and SW2, respectively, and the voltage obtained from the current detection resistors R1 and R2 is the A / D conversion circuit AD1, It is read into the control devices COM1 and COM2 via AD2. The control devices COM1 and COM2 hold the read values as input signals and supply them to an upper process control device or the like.

  Here, if the current input module 1 is the operation side and the current input module 2 is the standby side, the control device COM1 on the operation side generates the read signal Sr, turns on the switch circuit SW1, and reads the current signal. Further, the standby control device COM2 does not generate the read signal Sr.

  Therefore, the current from the current signal source SS flows only in the operating-side current input module 1 (current detection resistor R1) and is read into the control device COM1.

Japanese Patent Laid-Open No. 10-124117

  However, in the current input module as described above, normally, no current flows through the standby-side current input module 2, but due to a failure of the switch circuit SW2 or the control device COM2, the standby-side current If a current flows through the input module 2, a part of the current signal is shunted, and the current input module 1 on the operating side takes in an incorrect signal.

In general, the failure of the current input modules 1 and 2 is detected by the self-diagnostic function and notified to the host device. However, the protection operation for stopping the operation on the active side against such a failure on the standby side is Not done.
In addition, the current input module may be used not only as a double configuration but also as a single configuration. However, when a linkage part is provided between two modules in order to transmit fault information, etc. It may be difficult to change the duplex configuration and the single configuration.

  The present invention eliminates the disadvantages of the conventional apparatus as described above, and detects the current flowing through the current input module on the standby side when the dual configuration is adopted, and operates the current input module on the operation side. An object of the present invention is to realize a current input module that can be stopped and can be easily operated even in a single configuration.

In order to achieve the above object, according to claim 1 of the present invention, a current detection resistor is connected to a current signal source via a switch circuit, and a read signal for driving the switch circuit is generated by a control device. In the current input module configured to read the magnitude of the signal current flowing through the current detection resistor and hold it as an input signal,
A control device having a function of detecting the magnitude of a voltage generated in the current detection resistor in a standby state in a duplex configuration, and inverting the duplex signal when the voltage value is other than 0;
A duplex signal generated from the control device is input to one input terminal, and a high-level potential is input to the other input terminal in the single configuration, and a read control signal of the counterpart module in the dual configuration. Is selectively input and generates an OR output ; and
An output signal of the first logic circuit is input to one input terminal, and an operation signal generated from the control device is input to the other input terminal to generate a NAND output. And
The switch circuit is driven in accordance with a read control signal generated from the second logic circuit.

  According to a second aspect of the present invention, the current input module according to the first aspect further includes a switch drive circuit that receives the read control signal and generates a read signal for driving the switch circuit.

According to claim 3, at a current input module according to claim 1 or 2, wherein the control device, read back operation signal supplied to the duplexed signal supplied to the first logic circuit and or said second logic circuit, It has a function of performing self-diagnosis.

According to a fourth aspect of the present invention , in the current input module according to any one of the first to third aspects, the current input modules having the same configuration are connected in parallel to the common current signal source, and the read control signal is transmitted to the other party. The first logic circuit on the side is supplied.

According to a fifth aspect of the present invention , in the current input module according to the fourth aspect , the current input module to be operated is started up earlier than the current input module on the standby side.

As described above, the first and second logic circuits that receive the duplex signal, the operation signal, and the other party's reading control signal are provided, and the control device has a function of detecting the presence or absence of current input in the standby state. If the duplex signal in the standby current input module is inverted according to the detection result, it is confirmed that the current has flowed through the standby current input module in the duplex configuration. By detecting, the operation of the current input module on the operating side can be stopped.
In addition, by controlling the duplex signal input to the first logic circuit, it is possible to perform an operation independent of the state of the reading control signal on the counterpart side, so that connection for the duplex configuration is possible. Can be easily operated even in a single configuration.

  Hereinafter, the current input module of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a current input module of the present invention. The example shown in the figure shows a duplex configuration. In the figure, components similar to those in FIG. G11 and G21 are first logic circuits. A duplex signal dpxsel generated from the control devices COM1 and COM2 is input to one input terminal, and a reading control signal of the counterpart module is input to the other input terminal. The service is input and an OR output is generated. G12 and G22 are second logic circuits. The output signals of the first logic circuits G11 and G21 are input to one input terminal and generated from the control devices COM1 and COM2 to the other input terminal. The operation signal request to be input is input and a NAND output is generated. DR1 and DR2 are switch drive circuits that receive a read control signal service generated from the second logic circuits G12 and G22 and generate a read signal Sr that drives the switch circuits SW1 and SW2.

The duplex signal dpxsel is “0 (low level)” in the duplex configuration, and “1 (high level)” in the single configuration. The operation signal request is both in the duplex configuration and the single configuration. It becomes “1 (high level)”. However, the operation signal request on the operation side rises first.
If the current input module 1 is the active side and the current input module 2 is the standby side, the operating signal request of the control device COM1 on the operating side is "1" first, and the operating signal request of the control device COM2 on the standby side is delayed. Becomes “1”.

For this reason, when the operation signal request of the control device COM1 on the operation side rises, one input terminal of the first logic circuit G11 is maintained at a high level potential via the resistor, and the first logic circuit G11 The output of “1” is “1”.
Therefore, the output (reading control signal service) of the second logic circuit G12 is “0” and is supplied to the switch driving circuit DR1.
The switch drive circuit DR1 receives the read control signal service and turns on the switch circuit SW1.

As a result, the signal current from the current signal source SS flows into the current detection resistor R1 on the operating side, and is read into the control device COM1 via the A / D conversion circuit AD1.
In the current input module 2 on the standby side, the operation signal request is delayed to “1”, but the output (reading control signal service) of the second logic circuit G12 on the operation side is already “0”, Since the output of the first logic circuit G21 is “0”, the output of the second logic circuit G22 (reading control signal service) remains “1”, and the switch circuit SW2 is off.
For this reason, no current flows through the standby-side current detection resistor R2.

  FIG. 2 shows a truth table for explaining operations in the first and second logic circuits G11 and G12. (A) is the operation of the first logic circuit G11 that generates an OR output, and the counterpart logic circuit G21 performs the same operation. (B) shows the operation of the second logic circuit G12 that generates a NAND output, and the counterpart logic circuit G22 performs the same operation. The table also shows the state of the read signal Sr generated in response to the read control signal service.

  Now, in such an operating state, the control device COM2 on the standby side detects the magnitude (presence / absence) of the current flowing through the current detection resistor R2, and if the detection output is other than 0, it is determined as a failure, It has a function of inverting the duplex signal dpxsel to “1”.

  As a result, the output of the second logic circuit G22 (reading control signal service) becomes “0”, the first logic circuit G11 on the operating side is inverted, and the output of the second logic circuit G12 (reading control signal service). ) Is reversed, and reading of the signal current in the current input module 1 on the operating side is stopped.

  Accordingly, it is detected that a current has flowed through the standby-side current input module 2, and the operation of the operating-side current input module 1 is stopped, so that the operating-side current input module 1 reads an incorrect current input signal. Can be prevented. The failure information is also notified to the host device, and maintenance such as replacement of the device is performed.

  Furthermore, the control devices COM1 and COM2 have a function of reading back the values of the duplex signal dpxsel and the operation signal request generated by itself. For example, even if a signal “1” is generated, a signal “0” may actually be supplied due to a port failure or disconnection, and such a failure may be detected by reading back. Is possible.

  The state of the signal to be generated is compared with the state of the signal read back, and if they do not match, it is determined that there is a failure and the failure information is notified to the host device.

  Therefore, in each of the current input modules 1 and 2, a failure of the first and second logic circuits G11, G12, G21, and G22 can be detected as a failure in its own device, and in a duplex configuration. Therefore, it is possible to minimize the range of the common part where neither failure can be diagnosed.

  Also, in a duplex configuration, when a failure of the current input module on the operating side is detected and the operation is to be stopped, the operation signal request etc. on the operating side is not switched due to some problem, and the operation stops. Sometimes it is not possible.

  In such a case, if the duplex signal dpxsel is set to “1” in the standby-side current input module, the operation on the operation side can be forcibly stopped as described above, and the reliability is higher. A system can be realized.

  FIG. 3 is a block diagram showing another embodiment of the current input module of the present invention. In the figure, the same components as those in FIG. In the example shown in the figure, the current input module has a single configuration.

In the single configuration, a high-level potential is input to one input terminal of the first logic circuit G11, and the output (reading control signal service) of the second logic circuit G12 is supplied only to the switch driving circuit DR1. Has been.
Further, the duplex signal dpxsel is “1”.

  Therefore, the output of the first logic circuit G11 is “1”, the switch circuit SW1 is driven in accordance with the operation signal request, and the reading of the current signal can be controlled only by the operation signal request.

  Further, the failure diagnosis function by reading back the duplex signal dpxsel and the operation signal request is the same as that of the apparatus shown in FIG.

  In the above description, the case where the first and second logic circuits are configured by an OR circuit and a NAND circuit is illustrated, but the configuration of the logic circuit is not limited to this.

  Moreover, although the case where the switch circuit was comprised by FET was illustrated, the structure of a switch circuit is not restricted to this.

FIG. 1 is a block diagram showing an embodiment of a current input module of the present invention. FIG. 2 is a truth table for explaining the operation of the logic circuit used in the current input module of the present invention. FIG. 3 is a block diagram showing another embodiment of the current input module of the present invention. FIG. 4 is a block diagram showing an example of a conventional current input module.

Explanation of symbols

1, 2 Current input module SS Current signal source SW1, SW2 Switch circuit R1, R2 Current detection resistor AD1, AD2 A / D conversion circuit COM1, COM2 Controller G11, G21 First logic circuit G12, G22 Second logic circuit DR1, DR2 switch drive circuit

Claims (5)

A current detection resistor is connected to the current signal source via the switch circuit, and a read signal for driving the switch circuit is generated by the control device, and the magnitude of the signal current flowing through the current detection resistor is read as an input signal. In a current input module configured to hold
A control device having a function of detecting the magnitude of a voltage generated in the current detection resistor in a standby state in a duplex configuration, and inverting the duplex signal when the voltage value is other than 0;
A duplex signal generated from the control device is input to one input terminal, and a high-level potential is input to the other input terminal in the single configuration, and a read control signal of the counterpart module in the dual configuration. Is selectively input and generates an OR output ; and
An output signal of the first logic circuit is input to one input terminal, and an operation signal generated from the control device is input to the other input terminal to generate a NAND output. And
A current input module for driving the switch circuit in accordance with a read control signal generated from the second logic circuit.   2. The current input module according to claim 1, further comprising a switch drive circuit that receives the read control signal and generates a read signal for driving the switch circuit. The control device has a function of reading back a duplex signal supplied to the first logic circuit and an operation signal supplied to the second logic circuit, and performing self-diagnosis. Or the current input module of 2. 2. A current input module having the same configuration is connected in parallel to a common current signal source, and each read control signal is supplied to a first logic circuit on the other side. 4. The current input module according to any one of 3. 5. The current input module according to claim 4 , wherein the operation signal is raised earlier in the current input module that should be the operating side than in the current input module that should be the standby side .

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