PLC analog output module

摘要

As a configuration for detecting an occurrence of abnormalities such as a disconnection of output wiring or an overcurrent of a PLC analog output module that controls a load by an analog current signal, the PLC analog output module includes a current output circuit that outputs the analog current signal, a current sensing resistor provided at a current output terminal of the current output circuit for directly detecting an analog current output to the load, a monitoring circuit that monitors voltages at both ends of the current sensing resistor, and an abnormality detection circuit that discriminates whether there is an occurrence of a disconnection or an overcurrent based on a monitoring result of the monitoring circuit.

主权项

1. A PLC analog output module for controlling a load by an analog current signal, comprising:
a current output circuit that outputs the analog current signal; a current sensing resistor provided at a current output terminal of the current output circuit and on a side of a higher potential than the load, the load being provided between the current sensing resistor and ground, the current sensing resistor directly detecting an analog current output to the load; a differential circuit that outputs a differential voltage of voltages at both ends of the current sensing resistor; an abnormality detection circuit that receives the differential voltage output from the differential circuit and discriminates whether there is an occurrence of a disconnection and an occurrence of and overcurrent based on a determination result as to whether the differential voltage is equal to or lower than a determination value; the abnormality detection circuit using the differential voltage output commonly to discriminate the occurrence of the disconnection and the occurrence of the overcurrent; and a control module that changes and sets the determination value to be compared with the differential voltage in the abnormality detection circuit.