IO-Link or Analog Signal - Which Wiring Should You Choose?

What sets IO-Link apart from the analog signal?

IO-Link is a standardised point-to-point communication per IEC 61131‑9 that connects a sensor digitally to a master. The classic analog signal instead transmits the measured value as a continuous current (4‑20 mA) or voltage (0‑10 V) over its own line.

With an analog signal the physical value is converted into a proportional signal and recalculated in the controller through an A/D converter. Every conversion, contact resistance and cable length can distort the result. IO-Link transmits the same value digitally and therefore without signal loss right up to the final terminal.

How do diagnostics and parameter setting differ?

The biggest practical difference lies in diagnostics and parameter setting. An analog sensor only delivers its measured value - on a wire break the current drops to 0 mA and no further information is available. Alongside the process data, IO-Link also transmits service and diagnostic data such as operating temperature, contamination or switching cycles.

• Remote diagnostics: short circuit, wire break and overtemperature are reported as events, not just as a missing value.
• Parameter setting during operation: switch points, filters and ranges are written from the controller, without a potentiometer on the device.
• Automatic device replacement: on a swap the master reloads the stored parameters into the new sensor via Data Storage.
• Plain-text identification: manufacturer, type and serial number are read out, making goods receipt traceable.

With the analog signal every setting is instead made locally on the device. That is quick for simple applications but becomes laborious with many measuring points and is hard to document.

What does the choice mean for cabling effort?

IO-Link uses an unshielded 3-wire standard cable (M12, up to 20 m) and saves the shielded analog line. Because the signal is digital, the shielding and EMC effort that 4‑20 mA lines require in noisy environments is no longer needed.

For simple limit switches or very fast control loops with cycle times below the IO-Link response time the analog signal is often still the right choice. But as soon as diagnostics, frequent reconfiguration or many identical measuring points come into play, IO-Link clearly lowers cost over the life cycle.

Frequently asked questions