The following are some basic facts about input loop power sources: The input module usually isn't a loop power source. Although 120V is common for digital loops, other voltages are also used. There ...

Industrial control systems can be categorized in two types: open-loop and closed-loop systems. The open-loop control system is a continuous control system that provides no feedback from its output.

In our previous issue, we noted that the first step in troubleshooting digital input modules is to verify the power source of each loop. If input power is missing, the causes can be such things as ...