Open standard offers open dialogue

Last year Sick was the first company to offer a fieldbus-enabled standard sensor - the WT18-33 photoelectric proximity switch.

Last year Sick was the first company to offer a fieldbus-enabled standard sensor - the WT18-33 photoelectric proximity switch.

One year later it is fair to say that the technology used by the sensor and for the communication protocol - IO-Link - is firmly established and ready for wider implementation.

The standardisation of IO-Link, initiated by Sick and supported by many other sensor manufacturers, will shortly be completed - with most of the specification being defined and agreed.

This is reinforced by the fact that the German Electrotechnical Commission (GEC) has accepted the IO-Link open standard as a standardisation proposal for the International Electrotechnical Commission (IEC).

The most important advantages offered by IO-Link are increased plant availability, comprehensive remote diagnosis and automatic plant documentation.

Of particular importance for the chemical and pharmaceutical industries, it also offers the possibility of validating entire machines.

It is for these reasons that the fieldbus-enabled IO-Link sensor has very quickly received the attention that experts predicted.

One of the main technological drivers is the economical upgrading of an output signal-switching device to a communication interface.

Third-generation scanners, with their ASIC-based sensor design and the WL12G glass photoelectric switch, provide the best prerequisites for IO-Link.

Physically, IO-Link sensors can be coupled to fieldbuses, including Profibus, DeviceNet and Ethernet, via a connection module that will allow detection, communication and state information to be called up both from the machine's operating panel or a control room sited elsewhere in the installation.

IO-Link is not a classical bus system, but a fieldbus-neutral point-to-point connection infrastructure for dialogue between sensors and controllers.

This new concept not only permits the transfer of digital switching states and digitalised analogue values but also the transfer of considerable supplementary information.

This can include pre-contamination warnings, the presence of sources of interference in the sensor surroundings, the quality of the switching signal and the current scanning distance.

This dialogue between sensors and automation systems opens up completely new perspectives during the design, construction, installation, operation and maintenance of machines.

Machine manufacturers and end users can easily and rapidly profit from the advantages offered by IO-Link.

In addition to the use of dialogue-enabled photoelectric proximity switches from SICK (and corresponding sensors from other producers), an IO-Link connection module is all that is required for a fieldbus connection.

This advance permits connection of up to four sensors via unscreened, three-pole standard cables making it compatible with existing switching and connection technology.

It is also possible to connect sensors that are not communication-enabled, though these cannot use the dialogue advantages offered by IO-Link.

The numerous advantages offered by IO-Link are not achieved at the cost of process speed.

The rapidity of the communication dialogue is sufficient to exchange process data within 2ms.

The concept can also be expanded with a real-time output for very rapid switching processes.

Numerous end users and machine producers are now waiting for the products to become available.

Three sectors will be the first out of the starting blocks.

In the pharmaceutical industry IO-Link supports, among other things, rapid changes in ingredients and the validation of entire machines and plants.

The packaging industry profits through the automation of format-changing processes, as well as the dialogue-controlled adjustability of critical applications in which high accuracy and reliable reproducibility are vital.

In handling and warehousing systems, IO-Link makes it possible to see with the "eyes" of the sensor from distant locations.

As a result sensor optimisations, e.g to suppress passive background interference, can be carried out from decentralised locations without impairing application performance.

In summary, IO-Link will have positive effects on the design and control technology of future machines and plant.

Largely passive function elements will become active participants that are in dialogue with the control level and, in addition to switching signals, can autonomously report errors and supply state information.

IO-Link is very much perceived to be the sensor communication of the future.

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