4–20 mA vs 0–10 V vs RS485 vs IO-Link: Which Sensor Interface Should You Use?

• time：2026-10-10 15:10:18
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Choose the sensor interface by five application facts, in order: cable length, electrical-noise environment, whether you need remote diagnostics and parameter access, the update rate the control task requires, and which input modules the PLC already has. As working defaults: 4–20 mA serves long runs and noisy plants; 0–10 V suits short, clean in-panel runs; RS485 (typically Modbus RTU) serves multi-point digital reads over distance; IO-Link adds per-device diagnostics and parameterization where a master port is available. Verify each candidate against the sensor's data sheet and the PLC module specification before ordering — interface and module must be confirmed together.

Key Takeaways

• Distance and noise eliminate options fastest. Voltage signals degrade with cable resistance and pick up noise on long runs; current loops and differential serial links do not share those failure modes. A 100 m run next to drives is a different decision than a 2 m in-panel link.

• Analog answers "how much", digital answers "which value and why". 4–20 mA and 0–10 V carry one measured value per wire pair; RS485 and IO-Link carry scaled values, status and configuration over a digital protocol — different capability, different wiring, different PLC modules.

• 4–20 mA's live zero is a fault-detection feature. Below ~3.5 mA the loop is broken, not measuring zero — a general property of current loops that voltage output cannot replicate.

• IO-Link is a point-to-point technology, not a fieldbus. One port, one device, plus cyclic process data and acyclic diagnostics/parameters — it requires an IO-Link master and an IODD for the device.

• The PLC module decides as much as the sensor does. The best interface on paper still fails if the input module, scaling and scan behavior are not verified — check the full chain, as covered in the output-to-input integration guide ({{URL_F10}}).