How can signal isolation in HMI (Human Machine Delivery) systems improve EMC (Electronic Performance Control)?

Signal isolation technology in HMIs is a powerful means of improving EMC performance. It effectively breaks ground loops, suppresses common-mode interference, and improves surge immunity. Typical signals requiring isolation include analog sensor inputs, various communication interfaces, digital I/O, and digital input/output. Isolation methods mainly include optocoupler isolation, magnetic coupling isolation, and capacitive isolation. Optocouplers are commonly used for low-speed digital signals; magnetic coupling and capacitive isolation can be used for high-speed digital and analog signals. After isolation, the circuits on both sides of the isolation have their own independent ground references, thus eliminating common-mode interference caused by ground potential differences.

Simultaneously, the isolation barrier prevents noise from one side from being conducted to the other. For optimal results, isolation devices should be placed close to interference sources or sensitive components, such as immediately after communication interface connectors. The power supplies on both sides of the isolation must also be independent, typically requiring isolated DC-DC modules or transformers. In PCB layout, traces should be avoided under the isolation strip, and the ground planes on both sides should be clearly separated. Although isolation increases cost and complexity, it fundamentally solves many challenging EMC problems for HMIs operating in harsh industrial environments or requiring long-distance connections. E-Tech Electronics offers a variety of isolation chips and isolated power supply solutions to help HMI designs achieve higher EMC ratings.