IO-Link - the easy, quick, and efficient way to connect your sensors

Most process plants have auxiliary services that do not require sophisticated instrumentation; more basic sensors are adequate, while also being more cost-effective. IO-Link offers an easy way to integrate these devices. It comprises IO-Link masters (comparable to a remote I/O), each with IO-Link devices, which can be sensors or actuators, connected via standard three-core cables. It is typically a subsystem of a larger, plantwide monitoring and control network.

IO-Link master-device communication uses a digital point-to-point UART protocol rather than Fieldbus networking. This manages transfer of parameters to devices, and collection of diagnostic and measurement information from them. The IO-Link master exchanges data with higher levels through PROFINET, Ethernet/IP and many other protocols.

As an industrial communications networking standard, IO-Link’s devices, while more basic, still offer the data-rich visibility and controllability benefits of digital technology. The standard, defined as IEC 61131-9[i], has now evolved from V1.0 to V1.1.

What challenges does IO-Link address?

For traditional systems, parameter loading for system and machine commissioning has always been a costly and time-consuming factor. Time and expense can be similarly wasted in reloading parameters after instruments have been swapped out. And this parameterization must be performed online, causing further production delays.

This is also a problem in a system manufacturing environment. Time is lost as the same parameters are entered into each unit of a system production batch.

Once in operation, such systems can be prone to failure and downtime as sensors do not provide status data to help spot latent problems. Even without a significant system failure, identifying and diagnosing problems in traditional instruments can be difficult and time-consuming – and may require skilled technician expertise to resolve.

Logistics complexity and delays can also arise, as well as onerous stocking costs, if a process needs multiple devices with varying configurations. Often, differences between sensors can be small; 0 to 10bar vs 0 to 100bar, for example. Nevertheless, this represents a difference in parameterization, which may have to be performed by the instrument vendor.

This is exacerbated if each device type calls for its own cable and/or connector, possibly of elevated specification.

IO-Link is a solution that can be used anywhere except in hazardous areas. It offers answers to these issues through its communications capabilities. In a standardized environment, each sensor has a unique identification comprising a vendor ID and a device ID. It can continuously deliver data packets that include 32 bytes of process data, a status bit, parameter and diagnostic device data, and event data such as error messages.

Planning and parameterization of an IO-Link system can be performed using I/O Device Description (IODD) and an engineering tool. This allows easy device configuration, while stockholding for different device types is reduced. Parameterization can be performed remotely offline or online, using the engineering environment of the automation system.

Complexity on the factory floor is also reduced, as all IO-Link device types connect to their IO-Link masters via standard 3- or 5-core unshielded cables, and use industry-standard M12 connection plugs. Cables can be up to 20m in length.

Once the system becomes operational, maintenance, repair, and operation (MRO) is accelerated. New repair and maintenance concepts become possible, through IO-Link’s self-diagnosis and self-parameterization capabilities, with value added to process measurements by detailed status and error data. Sensors often provide other values, such as temperature, alongside the main measurement, or continuous measurement values alongside a switch status.

IO-Link functions as a compelling alternative to simply monitoring non-digitalized devices such as 4-20mA transmitters or digital input switches, which only permit one process variable per cable pair. Such devices also require scaling and local configuration – operations that must be repeated manually every time a device is exchanged.

How does IO-Link benefit users?

IO-Link offers easy and efficient integration, through using standardized function blocks. IO-Link also complements Industrial Ethernet well. High-end Ethernet devices can operate alongside more basic IO-Link sensors and actuators.

A traditional control system’s wide variety of sensors would have many different analog and digital signal types – Digital In (DI), Digital Out (DO), PNP, NPN, Pulse, 0 - 10V, and 4 – 20mA and possibly others. These would all generate requirements for their own connector and cable types; by contrast all IO-Link devices use a common standard cable, which reduces inventory, complexity, and installation time. Once installation is complete, commissioning and start-up is accelerated by automated parameter setting.

If problems occur, the system provides diagnostic information with cause and remedy; this includes cable break detection. If diagnostics indicate that a device needs changing, this can be facilitated through automatable parameter data storage and download.

The Endress+Hauser contribution

One advantage of IO-Link is its large community, with 145 member companies. Users can benefit fully from this wide choice, because all devices are interoperable if they comply with the IO-Link standard.

Against this background, one particular Endress+Hauser advantage is that they offer sensors to measure a wide range of process variables, including flow, temperature, pressure, level, and conductivity.

The Endress+Hauser sensor examples below demonstrate this product diversity.

• For level, Endress+Hauser offers the Liquiphant FTL31 point level switch for liquids. The FTL31 is designed for industrial applications in machine-building and all other industries. The Liquiphant is used for overfilling prevention or pump dry-run protection in cleaning systems. The IO-Link capability allows easy parameter setting and continuous self-monitoring, with no calibration required for plug & play operation. It provides reliable switching irrespective of the measured media properties.

• Pressure sensor: The Cerabar PMP23 is a price-attractive and compact absolute or gauge pressure transmitter. The piezo-resistive measuring cell with flush-mounted 316L diaphragm was designed for applications in the hygienic industry. PMP23 offers various EHEDG and 3-A certified hygienic process connections, materials with FDA conformity, EG1935/2004 conformity, IP69 protection, optional IO-Link, and hazardous area certificates. The device can be delivered with customized measuring ranges up to 40bar.

• Pressure switch: The Ceraphant PTP31B is a price-attractive pressure switch with piezoresistive sensor for safe measurement and monitoring of absolute and gauge pressure in gases, steams, or liquids. The pressure switch with compact design is extremely stable and overload resistant for up to +400bar. The IO-Link capability allows easy integration and parametrization of the device.

• Temperature: the iTHERM CompactLine TM311 thermometer measures the process temperature using a Pt100 sensor element (Class A, 4-wire). An optional integrated transmitter converts the Pt100 input signal. In the version with integrated electronics, the device automatically detects the connection variant (IO-Link or 4–20mA).

• Flow: The Picomag is the economical electromagnetic flowmeter for many applications in secondary circuits with conductive liquids in all industries. End customers, skid builders, equipment manufacturers and system integrators value the space-saving Picomag for its flexible installation capabilities. Additionally, its future-oriented, intuitive operation via Endress+Hauser’s SmartBlue app on every Bluetooth-enabled smartphone or tablet ensures fast, secure, and simple commissioning. Picomag provides simultaneous measurements of flow, temperature, and conductivity through its single IO-Link cable.

An important consideration for these and all other Endress+Hauser IO-Link devices is that each is fully compatible with the latest V1.1 version of IO-Link. IO-Link 1.1 enables data backup so plant personnel can save and reuse device parameters. It also enables data rates of 230.4 kBaud via IO-Link 1.1 primary devices, and can handle data widths of up to 32 bytes per port.

The V1.1 environment also means that device manufacturers like Endress+Hauser can design successors for other devices from the same family to maintain compatibility. If a failure occurs on a user’s system, the operator can install a compatible device without needing any software tools. Unlike V1.1 devices, no automatic device exchange is possible with IO-Link V1.0 sensors. Additionally, an IO-Link V1.0 master will not support V1.1 sensors.

Benefits of the Fundamental Selection

Endress+Hauser’s IO-Link sensors form part of their Fundamental Selection range, which in turn is part of their FLEX Selections strategy.

The Fundamental Selection comprises deliberately simple products with minimal numbers of variables, making selection easy. Compared to the other FLEX selections, there are also fewer features and options. Installation, maintenance and handling accordingly become considerably easier.

However, simplicity does not mean lower product quality. Endress+Hauser relies on the same component quality as for their other products. They also employ the same technologies as developed over the last 60+ years together with customers from a wide range of industries.

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