This article *** FDT, ifm, OPC and ODVA
Author |suzanne gill
By making field devices and sensors smarter, they are a key element in enabling manufacturing companies to implement digital transformation.
Traditionally, sensors and actuators have typically been devices with a single function, for example, a proximity sensor detects if an object is in its vicinity, and a valve actuator only opens or closes the valve. In the case of field devices, this type of single function came to be referred to as the "primary variable".
According to Steve Biegacki, managing director of the FDT Group, the adjective smart was first applied to the 3051 pressure transmitter at Fisher Rosemount in 1985, and it may have been the first digital field device ever produced, as well as the first field device to use a microprocessor to process the transmitter's direct measurements and convert them into standard signal types. The use of digital signal processing enables bidirectional data exchange between the transmitter and higher levels in the automation hierarchy, enabling the device to exchange more data than the primary variable, enabling multivariable data transmission and detailed diagnostic information about the transmitter's status.
Smarter field devices
In order to realize the intelligent functions of such devices, device descriptors need to be integrated into higher-level systems to inform the range of intelligent functions provided by the device. The FDT DTM (IEC62453) specification is one such feature. According to Steve, the application of the word smart to devices needs to meet the following requirements:
Digital microprocessors are used(usually ASIC) to collect process data generated by the transmitter and convert it into an industry-standard signal.
The ability to transfer more data than the primary variable, preferably with some sort of digital signal encoding method.
Support & Control Systemsor asset management applications for digitally encoded two-way communication.
Able to perform continuous self-diagnosisand transmit diagnostic status information to the upper levels of the automation structure for preventive maintenance through condition monitoring.
Able to pass through the control system, asset management applications, or dedicated programming devices to remotely configure, parameterize, and commission devices.
Through the same digital communication channelThe ability to exchange information on all additional features.
It is based on a standardized information modelDevice descriptors for architecture, which enable device detection at a higher level of control.
Therefore, a smart device can be defined as an instrument that has a certain degree of situational awareness of its environment and itself, and should also have the ability to communicate and exchange information in both directions with the upper echelons of the automated device in digital encoding. "In addition, smart devices must be clearly identified by higher-level control systems, asset management, and maintenance systems using standard information models. By performing this procedure, the equipment can be adapted to different working conditions. Steve concluded.
Advantages of IO-LINK
Peter Wienzek, Business Development Manager at ifm Electronics, agrees that sensors are not inherently intelligent. For decades, they only provided switching points or analog values. Advances in microprocessor technology have made them smaller and less costly, allowing automation equipment manufacturers to integrate more functionality into their equipment. The digitalization of sensors enables new intelligent functions. A smart sensor consists of a measuring unit, intelligent software functions, and communication interfaces such as IO-Link.
IO-Link is a serial, bidirectional point-to-point connection for signal transmission and energy**. Commenting on the advantages of IO-Link, Peter said: "Smart sensors with IO-Link provide logical data channels for cyclic process data and non-cyclic device data. "A typical example is a process sensor, which transmits temperature signals, service data, and events in addition to pressure, flow, consumption, or level signals. As a result, the images of machines and processes are getting bigger and bigger. Not only has the amount and variety of transmitted sensor data increased, but so has the speed and reliability. In addition, the sensor offers intelligent additional functions such as automatic calibration, drift detection, and data conversion directly.
In exemplifying smart actuators, Peter highlights the manipulators used in robotics and assembly applications. The electric robot provides power and IO-Link communication with just one cable. Servo-electric manipulators have many options for controlling the gripper position, gripping force and gripping mode. Thanks to the two-way communication capability of IO-LINK, the comprehensive feedback from the robot can also be transmitted to the controller via IO-LINK. This is a typical hybrid device application that integrates actuator functions, sensor functions, and a microprocessor for intelligent control.
It is clear that IO-Link is a common communication interface for smart devices, judging by the large number of IO-Link devices in the IO Device Description (Iodd Finder) database. It includes sensors, actuators, smart lights, displays, power supplies, eFuses and drivers, among others. Every IO-Link device is equipped with an iODD, and all of its functions must be recorded in machine-executable XML format. With this universal IODD standard, all IO-Link devices can be configured via a manufacturer-independent software.
The communication interface is key
According to Peter Lutz, Head of Field Communications at OPC, if a field device has certain functions, such as collecting and processing data, then both sensors and actuators can be considered intelligent. "The degree of intelligence can start with some basic data pre-processing and filtering, and gradually transition to highly complex algorithms including machine learning and artificial intelligence," he said. However, field devices often do not work in isolation, but are connected to a variety of other devices, which means that connectivity has become one of the key drivers of digital transformation. ”
In smart field devices, communication interfaces play an important role in providing raw or pre-processed data to external devices or software applications that perform data acquisition and data analysis.
Traditional field communication interfaces are often limited to field applications. This interface enables a point-to-point connection between a field device and a controller, or a fieldbus for the connection of multiple controllers or field devices. But the main drawback of these traditional communication interfaces is that they don't scale to the edge or even the cloud, which is the way Industry 4 is enabled0 and the key to the IIoT concept. The solution is provided by a gateway or protocol converter, or a controller performs a protocol or data conversion task.
The OPC UA (IEC 62541) framework provides a complete, open, standardized, and interoperable communication solution with built-in security that not only meets the requirements of industrial communication, but also enables consistency and semantic interoperability from the field to the cloud and vice versa.
To achieve this, OPC UA is being used in conjunction with different services (client-server and publish-subscribe) that are combined with different underlying communication protocols (e.g. UDP and MQTT) and a suitable physical layer (e.g. Ethernet-APL). Peter explains: "With this approach, with additional device companion specifications developed by numerous organizations around the world, information can be made available in standardized semantics directly in the data source, if possible. ”
For example, once plugged into the APL (Advanced Physical Layer), the flow meter directly provides standardized OPC UA flow measurement data. Similarly, servo drives directly process standardized OPC UA drive setpoints and provide standardized OPC UA actual drive values when integrated into machine networks configured with Ethernet TSN (Time Sensitive Networking).
According to Peter, "OPC UA devices and systems enable seamless communication regardless of the manufacturer or location, whether in the IT or operational technology space, improving interoperability and reducing integration costs".
OPC's Field Communication (FLC) program is actively expanding OPC UA to meet the needs of other applications in the field, such as deterministic, functional safety, motion, instrumentation and IO. Peter concludes: "It can be expected that in the future, field devices will become smarter by adding enhanced features, such as the regular exchange of real-time critical and safety-critical data, while having secure connectivity to the edge or cloud via OPC UA with vendor-independent data semantics. ”
Single Pair Ethernet
Steve Fales, Marketing Director at ODVA, also explains that one of the essential features that make sensors and field devices smart is the microcontroller, which includes a processor and memory that converts the sensor's analog signal into digital communicationProvide device diagnostics;Pass multiple process variables;Even perform internal calculations. Smart sensors and devices also enable digital communication via industrial communication networks such as Ethernet IP.
In addition, smart sensors can communicate digitally in another way: IO-Link. Steve explains, "The advantage of IO-Link is that it generates a digital signal;However, the disadvantage is that the gateway is required to convert IO-Link to an industrial Ethernet protocol such as Ethernet IP. He thinksSingle Pair Ethernet (SPE).It is a future-proof solution that will make low-cost sensors and devices smarter. Single Pair Ethernet will allow devices to power and communicate over long distances over a single twisted pair cable. One of its key advantages is that gateways typically don't need to convert data from smart sensors and devices because they already communicate via Industrial Ethernet.
One of the main variants of Single Pair Ethernet is Ethernet-APLIt combines 10BASE-T1L SPE, IEC TS 60079-47 2-WISE intrinsic safety and IEC 61158-2 Class A fieldbus cable to achieve a transmission speed of 10 Mbit-seconds, a transmission distance of up to 1000 meters, the ability to deploy in hazardous areas, and easy installation to meet the needs of the process industry. Ethernet-APL aims to revolutionize process automation by moving from 4-20 mA enabled devices to Ethernet-enabled devices. These devices will implement multiple process variables, commissioning in seconds instead of minutes, and can also be commissioned remotely, moving from reactive maintenance to diagnostics and functional, as well as easily communicating with the edge or the cloud.
While an analog device is generally not considered to be smart, its electrical signals can be converted into digital signals by another smart device, allowing the information it collects to be used by edge devices, MES or CMMS systems, or sent to the cloud for operational improvements. According to Steve, it's important to have a digital plan for critical equipment so that existing analog output can be translated into diagnostics and ** to reduce manual maintenance activities that can lead to unplanned downtime.
Given the advent of new low-cost smart sensors and devices, and the increased difficulty of finding workers performing low-value-added tasks, the days of maintenance personnel holding clipboards to collect data and check the condition of equipment are gone.
Key Concepts:
The degree of intelligence can start with some basic data pre-processing and filtering, and gradually transition to highly complex algorithms including machine learning and artificial intelligence.
It's important to have a digital plan for critical equipment so that existing analog output can be translated into diagnostics and ** to reduce manual maintenance activities that can lead to unplanned downtime.
Think about it:
How intelligent are your plant's field equipment?
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In the September 2023 issue of Control Chinese Engineering China, Technical Articles: How to Make Field Devices and Sensors Smart?
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