EMI

Many sensors work well on the bench, then fail once the cable becomes long.

A door sensor toggles randomly. A water leak probe alarms without water. An external button triggers by itself. An analog voltage input shows strange spikes. The issue gets worse near motors, relays, or inverters.

These problems are often called “interference,” but a long wire is not just extra copper. It turns an on-board input node into a field-exposed system.