| 摘要 |
PURPOSE:To perform self-diagnosis without providing a route for self-diagnosis independently by mounting plural pairs of inputs and outputs on the same package and using an input circuit in two stages. CONSTITUTION:In an analog input circuit 30, the circuit 30 is connected to the side of a detecting terminal 1 by a changeover switch 31 to read process signals. Since operation results of a computer are outputted to a D/A converter 42, this output is converted to a feedback voltage by a feedback resistance Rf, and this voltage is read to check whether the output of the computer is outputted correctly to an operation terminal 2 of a process or not. That is, the feedback voltage is led to a signal amplifier 32 by the switch 31, and the output is subjected to A/D conversion through a multiplexer 33 and is sent to the computer, and it is compared with the preceding value, which the computer outputs to discriminate normalcy/abnormality. Thus, the output to the operation terminal is read back and checked to diagnose input/output devices of a control loop simultaneously. |
