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IO-Link technology: How does IO-Link work?
The IO-Link chip is embedded in almost all of ifm's sensors at no extra cost. Even if you are only using the analog signal or a switching output from a specific sensor, the sensor processes much more data. Without IO-Link communication, this data is trapped inside the sensor.
Unlike a fieldbus system, IO-Link works using a straightforward point-to-point communication method with conventional 3-wire sensor and actuator connections. IO-Link unlocks the trapped data and transmits it to higher level systems for predictive maintenance and process quality improvements, as well as actionable insights not otherwise available.
Traditionally, the control world could only accept binary or analog signals and, therefore, only had limited information. More data required more inputs or analog cards, which are expensive and require more labor for wiring.
Today’s sensors process a lot of data, but without a pathway to the controller, it is trapped inside the sensor. IO-Link technology intergrates with PLCs and IIoT technology.
IO-Link offers three general types of data that vary from sensor to sensor: Cyclic, acyclic, and events data.
Digital measurements values (Cyclic data)
Regular, automatic, and periodic exchange of process data between the IO-Link master and its connected IO-link devices. This type of information is requested continuously from the controller and is needed to control machines or processes. The actual data is defined by the IODD and varies by device. Typical data includes:
- PDI (process data inputs)
- PDO (process data outputs)
- High level diagnostic information
The example below shows the difference between traditional outputs available for a flow meter vs. the data available via IO-Link.
Traditional sensor
2 wires, user chooses ouputs
- Switching output for flow
- Switching output for temperature
- Pulse output for totalization
- Frequency output for flow
- Frequency output for temperature
- Input for counter reset
IO-Link sensor
All data over 1 wire
Cyclic data
- Flow rate
- Temperature
- Totalized volume
- Device status
Acyclic data
- Max and min flow rates
- Max and min temperatures
- Totalizer memory
- Serial number and revision verification
- Simulation mode
- Configuration parameters
Events data
- Incorrect parameters
- Sensor out of range
The IO-Link master transmits machine data, process parameters, and diagnostic information to a PLC controller or directly to a higher level IIoT controls system. The 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.
A ports are standard for most connections on IO-Link masters. B ports are used on some output devices like valve manifolds and smart LED lights when extra power is required by the devices.
On A ports, pin 2 is always used as a digital input and pin 5 is not connected. ifm's DataLine (AL13xx) and CabinetLine (AL19xx) masters are offered with only A ports. These devices are limited to 300 mA load current per port.
On B ports, pins 2 and 5 provide an additional isolated supply voltage to connect IO-Link output devices that require increased power. With the introduction of the PerformanceLine masters (AL14xx), we can now switch loads up to 2A.
The ifm Y-path enables machine control via a PLC while offloading big data processing to higher-level systems, ensuring seamless machine operation without interference.
The PLC has been a mainstay of automation since the 1970s. It controls industrial automated equipment. With the advent of Ethernet technologies and IIoT applications, PLCs are asked transmit more information not necessarily used for machine control.
The PLC uses less than 20% of the sensor information for machine control. Data size of this information is in bytes, and cycle time in ms. HMI, visualization computers, servers, PCs, etc. use 80% of the sensor information. Data size is in Mb and cycle time is in seconds.
But what if we could allow your sensors to talk directly to your SCADA, MES, ERP and CMMS systems without intervention of the PLC and still send the information to the PLC for machine control?
This is now possible with the Y-path from ifm. Our IO-Link masters have a separate IIoT port with a dedicated IP address for the IT infrastructure. It does not affecting the machine control side of the system. This unique approach allows you to send information and data directly where you need it.
The IODD (IO-Link Device Description) is a compact file describing how IO-Link devices communicate information to higher level systems or controllers. It provides details about both cyclic data structure and available acyclic commands.
The IODD facilitates seamless integration of sensor devices into control systems. It offers a clear overview of communication behavior and structure.
Details on how to use the IODD can be found in the after-purchase setup and support section of this website.