Testing a communication relay with a multimeter is a crucial skill when troubleshooting electronic systems. Communication relays play an essential role in switching signals, and ensuring they are functioning correctly is key to maintaining the integrity of the system. A malfunctioning relay can disrupt operations, so knowing how to test it accurately is important. In this article, we will explain how to test a communication relay using a multimeter, covering both the coil and contact sides of the relay.

1. Understanding the Relay and Its Components A communication relay consists of two primary parts： the coil and the contacts. The coil is an electromagnetic component that, when energized, creates a magnetic field, causing the contacts to either open or close. The contacts themselves are divided into Normally Open (NO) and Normally Closed (NC) configurations, which determine the relay’s switching behavior. NO (Normally Open) Contacts： These contacts are open when the relay is not energized. When the relay is activated, the NO contacts close to allow current to pass. NC (Normally Closed) Contacts： These contacts are closed when the relay is not energized. When activated, they open, cutting off the current flow.