Over the years, sensors/actuators and their wiring have moved from purely analog (typically 4-20 mA or dc volts) to combined analog/digital (e.g., HART) and finally to 100% digital networks. During these years, plant engineers have seen more than their share of incompatible and proprietary networks, whether at the simple hardware, networking or application layer.
Recognized as an international standard, IEC 61131-9, IO-Link is a standardized, bidirectional communications protocol supported by sensors or actuators—which are connected through a master—which then connects to a controller, e.g., PLC, DCS, IPC or other. This networking solution provides users with more information about their devices, and it allows them to have remote access to the IO-Link master through industrial Ethernet networks, such as PROFINET or EtherNet/IP.