Dry contacts and wet contacts remain two of the most confused basics in industrial automation, PLC wiring, and building control. The whole difference sits in one question: does the contact carry its own power? A dry contact is a passive switch. It supplies no voltage or current, only opens or closes

A dry contact, also known as a volt-free or potential-free contact, refers to a passive mechanical switch contact that carries no built-in voltage or power. It only provides two states: open circuit or closed circuit. Unlike active wet contact signals, dry contacts require an external power supply t