What you'll learn
Connect a three-wire IO-Link sensor to Port 1 of an IO-Link master and link the master to the PLC network. L+ and L− power the field device; C/Q carries bidirectional point-to-point process data, parameters and diagnostics.
Lab time: ~18 minutes.
Lesson briefing
IO-Link Master and Smart Sensor
Connect a three-wire IO-Link sensor to Port 1 of an IO-Link master and link the master to the PLC network. L+ and L− power the field device; C/Q carries bidirectional point-to-point process data, parameters and diagnostics.
The device in the real world
IO-Link lets a smart sensor talk to an IO-Link master over a simple unscreened three-wire cable up to 20 metres. The same cable carries the 24 V supply and a data line called C/Q. The master collects data from up to several ports and passes it to the PLC over the plant Ethernet network, so the PLC can read process values and change parameters without a laptop at the sensor.
Why it is wired this way
IO-Link is not an Ethernet fieldbus at the sensor. The unshielded three-wire device lead runs only to the master. The master translates IO-Link data into the plant Ethernet protocol and must be separately powered and earthed.
Worked example
Plug a distance sensor into Port 1. L+ and L- bring 24 V to the sensor, and C/Q carries the measured distance as digital data. The master packages that value and sends it over Ethernet to the PLC, which can also write a new switching point back down the same wire. If the C/Q conductor comes loose, the sensor stays powered, but the master reports lost communication, because there is no data path. Wire the lab by powering the master first, then Port 1 to the sensor, then the Ethernet links.
Common mistakes
- Swapping L+ and L- at the sensor.
- Treating the sensor cable as Ethernet. It is point to point and never goes to a switch.
- Forgetting to power the master or switch separately from the PLC.
- Leaving the master earth terminal unconnected.
What you can now do
You can connect an IO-Link device to a master and the master to the PLC network, and explain what each of the three sensor wires carries.
Commissioning standard
Check the link status LED on the master port and read the device identity from the PLC before trusting any process value.
Hints
Power and earth the master before connecting the field port.
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This lesson uses 7 placed components on the lab canvas. Components are vendor-neutral (no proprietary trademarks); the wiring rules apply to any equivalent industrial part.
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