IO-Link fully integrates sensor technology into the overall communication system, permitting communication with sensors and actuators.

Sensors check the status of machines. When equipped with IO-Link, such sensors allow data to be collected and transmitted, enabling communication with the process controller from the most fundamental level of a factory. This is why the industrial automation sector views IO-Link as a crucial prerequisite and engine of the fourth industrial revolution - Industry 4.0.

To be economic, highly individualized products must be manufactured under the resource-efficient conditions of much more flexible mass production. At the same time, systems must be able to react quickly to changing market conditions. All this depends on new manufacturing technologies, including appropriate software solutions and the networking of individual processes. With the development of IO-Link as a globally standardized communications interface (IEC 61131-9) and its implementation in sensor technology, a crucial step has been taken towards Industry 4.0.

Communication with Sensors and Actuators

IO-Link fully integrates sensor technology into the overall communication system, permitting communication with sensors and actuators. Devices are detected, parameterized and diagnosed. This includes querying the cyclic device status using process data. Such information as the serial number or parameter data (e.g. sensitivities, switching delays, characteristic curves) are read or written via the IO-Link protocol.

This allows process parameters to be adjusted by the programmable logic controller (PLC) during operation. But IO-Link is not a fieldbus. Its technology is more like a USB interface, with point-to-point communication between a master and a device. The IO-Link master usually combines with the PLC to form the gateway to such fieldbuses as Profibus, Profinet and EtherCAT.

During the installation and start-up of milking machines, an IO-Link solution permits the automatic reading of sensor ID and sensor diagnosis, ensuring reliable operation.

IO-Link technology replaces parallel wiring and analogue signal routing. It allows the polling of sensor temperature, power supply, functional status and switching cycles – including remote diagnosis. In addition, switch output function can be set as normally open (NO) or normally closed (NC) via IO-Link.

The Swiss sensor specialist Contrinex is also convinced of the future of Industry 4.0 and the importance of IO-Link in this context. It therefore equips all new sensors with IO-Link, provided they have a PNP output and Contrinex ASIC or microcontroller.

With a robust and intelligent point-to-point communication system, sensors can transmit device and parameter data clearly to an IO-Link master. This technology is not reserved only for complex sensors. All the new standard series have the IO-Link interface. The user decides whether to take advantage of IO-Link, or use the standard output. The device is the same – and so is the price.

IO-Link for Responsive Maintenance

All inductive sensors from the Classics family already have IO-Link, allowing continuous monitoring of a sensor’s operating status. If there is a fault (e.g. wire break, undervoltage, LC oscillator break) or if the wrong sensor has been installed, appropriate information will be forwarded to the controller via IO-Link.

Moreover, to ensure that the sensor is not operating near the limits of its technical capabilities, sensor switching status can also be monitored not just for the actual signal, but also for the status at 80 percent of the operating distance. Any necessary repair, maintenance or replacement measures can therefore be initiated as quickly as possible.

Another IO-Link functionality of Classics family sensors is the detection counter. It counts the number of switching events detected, so that the number of parts or their speed can be calculated. A single IO-Link message resets the counter. In addition, the sensor’s internal temperature can be communicated to the controller via IO-Link. This information can be used to infer the ambient temperature in the application. Furthermore, since the maximum temperature is stored, this also supports machine diagnostics and maintenance.

IO-Link for Reduced Maintenance Inventories

Another interesting functionality of sensors with IO-Link, particularly regarding inventory management, is the possibility of selecting the circuit type. Thanks to this new communication technology, a single sensor type can be configured either for NO or NC operation, as each application requires. This halves the number of sensors that have to be kept in stock.

Application-dependent programming of a turn-on or turn-off delay (Delay or Stretch) is also possible: the switching timer allows a sensor signal to be delayed or stretched as required. All settings remain the same, even for standard sensor operation without IO-Link master.

Future Developments

In addition to the inductive Classics sensors, Contrinex has already integrated IO-Link into its photoelectric contrast sensors and small fibre-optic amplifiers. The company is also integrating IO-Link in all its full-metal inductive sensors. In future, every new product and every new sensor series will be equipped with IO-Link. This applies in particular to photoelectric sensors, in which IO-Link allows remote adjustment of the sensing range. This does away with direct adjustment on the sensor itself, either via potentiometer or a ”teach-in” button.

IO-Link is the prerequisite by which Industry 4.0 works - it is the interface for factory automation. Increased standardization of data organization and sensor profiles can therefore be expected. For IO-Link users, this would have the great advantage of always being able to find specific data at the same defined address - regardless of the sensor manufacturer.

Application Examples

The applications for sensors with IO-Link are as diverse as the industry as a whole. Whether used in milking machines or packaging equipment, the benefits of the new technology are obvious. For example, during the installation and commissioning of milking machines, checks to ensure that the right inductive sensor is at the right place previously took place manually.

Since every sensor had to be checked one by one, this process took a very long time. Also, due to the human factor, it was impossible to exclude errors. An IO-Link solution not only provided enormous time savings, but also increased reliability, because it allowed sensor ID to be read automatically and sensors diagnosed individually.

Another example: during the packing of chewing gum with ten strips per pack, ten fibre-optic amplifiers with specially focused optical fibres check the presence of each individual strip. Since each variety of chewing gum has a different colour, the sensors must be adjusted to the colour of each new one.

If fibre-optic amplifiers with IO-Link are used here much tedious, manual, job-by-job configuration can be avoided. Then, for any change of variety or colour, a simple download is enough to adjust each sensor for the new task. Significant time savings and increased process reliability result from switching to IO-Link.

IO-Link sensors - The advantages at a glance

• Continuous monitoring of process data
• Continuous diagnosis of sensor status
• Advanced parameter settings
• Central data storage
• Simple check of sensor ID, to ensure the right sensor is in the right place
• No manual setting of parameters; parameter sets are loaded automatically
• Plug-and-play sensor replacement
• Reduced downtime for machine setup

IO-Link

IO-Link is the name of a communication system for connecting intelligent sensors and actuators to an automation system, as standardized in IEC 61131-9 under the description: Single-Drop Digital Communication Interface (SDCI) for Small Sensors and Actuators. The standard covers not only the electrical connection data, but also a digital communication protocol used by sensors and actuators to communicate with the automation system.

An IO-Link system consists of an IO-Link master with one or more IO-Link devices (sensors and actuators or combinations of both) and a standard 3-wire sensor/actuator cable. The IO-Link master provides an interface to the programmable logic controller (PLC) and controls communication with connected IO-Link devices. The master may be a device of any construction or protection class.

References and sources:
IO-Link www.io-link.com
Industry 4.0 www.bmbf.de/en/19955.php
Contrinex www.contrinex.com

Pierre-Yves Dénervaud

Product Manager, Contrinex AG, Switzerland,

Pierre-Yves.Denervaud@contrinex.com