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IO-Link: What it is, how it works, and why it's important

IO-Link is a worldwide open-standard protocol for communications networking. It is used for communication between devices in industrial settings. An IO-Link system is bi-directional. It exchanges data between a master device, actuators and sensors.

IO-Link is the foundational technology of Industry 4.0. This digital communication network provides raw sensor values for more accurate data from your machines. It also eliminates the need to scale analog signals. 

On this page, We'll explore how this open-standard protocol works. You'll also learn how it can improve your facility’s productivity, maintenance, and expenditures. Finally, We'll compare this technology compares to similar industrial communication solutions.

IO-Link benefits

Digital real-time communication and easy data retreival are the backbone of IO-Link's important benefits for facilities in many industries: 

Improved product quality

100% digital communication is more reliable and accurate than an analog signal. And, predictive information from sensors improves product quality and instrument verification processes.

Lower costs

Reduce expenses by eliminating analog input cards and reducing the size of control cabinets.

Increased efficiency

Reduce cycle time for recipe changes with bidirectional communication between process instruments and a higher level controller.

Improve machine uptime

With the automatic device replacement feature of IO-Link enabled sensors, parameters from an existing device are automatically downloaded onto the replacement device. This minimizes unplanned downtime and gets your machine up and running faster.

Unlock the potential of your machines with digital communication

What if you could get more information without increasing cost, engineering time and complexity? What if we told you your existing infrastructure could already provide more insight?

IO-Link's digital, bidirectional, point-to-point interface integrates with virtually any automated system. The result is a 100% digital path to your PLC from a field-mounted sensor.

Unlike a fieldbus system, it works using a straightforward point-to-point communication method with conventional 3-wire sensor and actuator connections.

Using wired or wireless configurations, this technology overcomes integration challenges and allows devices to seamlessly share enriched data sets.


What is an IO-Link master?

The IO-Link master replaces a traditional analog input card with a digital communication path between the master and device. Up to 8 IO-Link devices such as sensors, valves, and I/O modules can be connected to a single master depending on the configuration of the master. The master transmits machine data, process parameters, and diagnostic information to a PLC controller or directly to a higher level IioT controls system.

Diagram of connections between an IO-Link master module and IO-Link device and diagram of IO-Link plug with signal and voltage information.

Unlock the potential of your machines with digital communication

Why has this technology been accepted so quickly?

This communications protocol has grown exponentially over the last decade for a number of reasons.

Chart showing the number of IO-Link nodes in use rising from less than 2 million in 2012 to 37/5 million in 2022

Reduced complexity

Scalable technology from simple binary On/Off devices up to smart IO-Link enabled sensors provide complete process transparency that quickly integrates into existing controls architecture.

Reduced cost

Savings of approximately 50% per point on input cards without the need for analog PLC cards.

With ifm, there is often no impact on sensor cost because the communication is already available in most of our sensors.

Minimal changes

Replacing analog communication requires few changes to controls architecture. And, each device can be connected using standard 3-wire unshielded cabling.

Comparisons to other communication technologies

IO-Link combines the best of all worlds with the functionality of analog signals and intelligence of Ethernet communication at the cost of binary On/Off points.

  Sensor communication
  Binary On/Off Analog IO-Link Ethernet based
Amount of data 1 bit 16 bits 32 bytes Many bytes
Sensor diagnostics    
Remote sensor parameter adjustment    
Automatic sensor parameter replacement    
Standard sensor cordsets  
Digital communication    
Complexity to integrate


IO-Link vs. Standard Analog Wiring

Analog systems are still in use at many facilities and are less expensive to install then IO-Link. However, they suffer from data losses when the signal coverts from analog to digital so it can integrate with modern software. The data losses become more severe in setups with multiple conversion points.  IO-Link is fully digital, avoiding any data losses even connection span large distances. 

IO-Link vs. HART

HART protocol is well-known, especially in the food and beverage, pharmaceutical, and chemical industries. Like IO-Link, it provides bidirectional communication of data between sensors and the controls system. Digital and analog signals are transmitted over cables. Integrating HART requires specific programming knowledge.

ifm and IO-Link

In the rapidly-evolving landscape of industrial technology and automation, ifm is committed to innovation, efficiency, and conserving resources. We’re dedicated to universal protocols and advancing interconnection between ecosystems.

ifm is a founding member of the IO-Link consortium. This group works with industry leaders to further the technology and integration, upholds quality standards, holds workshops, and more. The consortium has more than 250 members and counting.

Connected ecosystems

ifm offers one of the largest selections of sensors and other IO-Link-compatible devices. Our broad offering allows you to implement a comprehensive digital communication system on all your machines and processes.