Programmable logic controllers (PLCs) play a central role in today's industrial automation systems. They connect measuring instruments and actuators connected via conventional cabling to the process. However, a PLC is not completely decoupled from the industrial environment, so overvoltage peaks and transient currents can certainly affect its functionality. In addition, its range of application is often limited to 24 VDC and 100 mA. In order to adjust the applied voltage and/or current and to provide the PLC with suitable galvanic isolation, the appropriate interface should be installed for each input/output point, which both regulates the voltage and current level and offers isolation protection. The relay and optocoupler series from ABB offer such interfaces. They allow a wide range of adjustment of the voltage (from 5 to 400 V) and current (from 1 to 16 A) as well as a high level of isolation between input and output of 2 to 4 kV.
