How to prevent interference with EPS dry contact signals?

Although EPS dry contact signals (such as relay outputs and digital inputs) are in a switching state, they are susceptible to interference, leading to malfunctions. Anti-interference measures include:

1. Input-side anti-false triggering: For digital inputs, connect an RC snubber circuit (e.g., 0.1μF + 100Ω) in parallel across the contacts to absorb jitter and spikes; use a Schmitt trigger for shaping; and perform debouncing in software.

2. Output-side anti-interference emission: For relay outputs, connect a freewheeling diode or RC/TVS snubber circuit in parallel across the coil to suppress reverse voltage peaks; connect an RC circuit (e.g., 0.01μF + 47Ω) or a varistor in parallel across the contacts to reduce arcing and noise during opening and closing.

3. Wiring isolation: Dry contact signal lines should use twisted-pair cables and be kept away from power lines. If possible, use shielded cables and ground the shield at one end (usually on the PLC/DCS side).

4. Isolation relays: For important or long-distance dry contact signals, use opto-relays or isolated solid-state relays to achieve electrical isolation.