OPC Tutorial
Printed version of the online multimedia tutorial To view the online version visit: www.matrikon.com/tutorial
Welcome & Introduction Hello! My name is Randy Kondor and I am Matrikon’s OPC Product Manager. As you may already know, OPC is one of the world’s fastest growing standards for the exchange of process control data. This vendor independent multimedia presentation provides a quick introductory overview of OPC to point you in the right direction with minimal effort. We will talk about the vision of OPC, cover a case study, and provide more information about the various OPC specifications. After this presentation you will understand the basics of OPC and the knowledge required to begin integrating OPC into your current system. To get started, please choose from one of the modules in the main window. Module 1 OPC Basics: Introduction to OPC Module 2 Case Study: Proprietary versus OPC Connectivity Module 3 Background Information: The OPC Foundation & OPC Specifications Module 4 OPC DA: Real-Time Data Access Module 5 OPC HDA: Historical Data Access Module 6 OPC Summary: Additional Resources
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Module 1: OPC Basics Introduction to OPC Introduction to OPC • • • • OPC standardizes the communication of process control data OPC standardizes on a technology rather than a product OPC provides true interoperability and scalability OPC reduces implementation time and costs
The purpose of OPC is to provide a standards-based infrastructure for the exchange of process control data. For example, manufacturers have many different data sources such as PLCs, DCSs, databases, gauges, RTUs and other devices. This data is available through different connections such as serial, Ethernet, or even Radio transmissions. Different operating systems like Windows, UNIX, DOS and VMS, are also used by many process control applications.
In the past, vendors would capture this data in their own applications using their own device interfaces. The data would be kept in a proprietary format, which meant that you could only access your data using tools from the same vendor who originally locked the data. You were then forced to return to that vendor every time you needed a system change or expansion.
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In contrast, OPC standardizes on a technology rather than a product. By using the OPC set of standards, data can be passed from any data source to any OPC compliant application. These applications include Human Machine Interfaces (or HMIs), trenders, spreadsheets, data archivers, Enterprise Resource Planning applications, and others. OPC is a communication standard that provides true interoperability and scalability. This enables you to visualize, analyze, report, or do anything you want, with applications from almost any vendor using one or more of the OPC specifications. By selecting the standards-based OPC technology, you enable true interoperability, reduce your implementation costs, and build a fully scalable system for the future.
OPC Definition OPC is a published industrial standard for system interconnectivity. The OPC Foundation maintains all the OPC specifications. OPC stands for OLE for Process Control. It uses Microsoft’s COM and DCOM technology to enable applications to exchange data on one or more computers using a client/server architecture. OPC defines a common set of interfaces. So applications retrieve data in exactly the same format regardless of whether the data source is a PLC, DCS, gauge, analyzer, software application or anything else. As a result, OPC is as an out-of-the-box, plug and play communication solution.
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Module 2: Case Study Proprietary versus OPC Connectivity Common Plant Requirements • • • Petrochemical plant needed to monitor equipment Three different applications were needed to analyze data Three different devices generated data
To better understand OPC, let’s have a look at a specific example. In this case, a very large petrochemical plant wanted to monitor their turbines using three applications; a Human Machine Interface, or HMI, for visualization, a Process Historian for data storage, and a machine condition monitoring application. The data would come from three different data sources; a PLC, a vibration monitoring system, and a calculation engine. Heading into the project, the plant had three common requirements: 1. Minimize device loads by minimizing data requests 2. Quickly and easily implement a communication infrastructure 3. Minimize implementation and acquisition costs
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The Proprietary Solution • • • Proprietary solution required many custom drivers Multiple device drivers would create too many data requests Lengthy implementation time and excessive costs incurred
The first option was to use the proprietary connectivity method. Each application would communicate with each data source using its own interface, or driver. The HMI needed three drivers to communicate with each of the data sources. One to communicate with the PLC using the TSAA protocol, a second to retrieve data from the vibration monitoring system using Modbus, and a third to retrieve preconfigured calculations from the calculation engine using DDE. The process historian also needed three drivers as did the machine condition monitor. In total, nine custom drivers were needed.
In this case, you will notice that each data source would have had to provide the same data three times: once for each application and its associated driver. This would have created a tremendous load on each data source due to an excessive number of data requests.
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It was estimated that it would take approximately 10 days to complete the installation and commissioning of the drivers, at a cost of over $50,000 for the software and associated labor.
The OPC Solution • • • • OPC solution minimizes devices drivers OPC drivers are readily available OPC reduces device loads significantly Implementation time and all costs drastically reduced
Now let’s take a look at the OPC solution using the same data sources and software applications. Here, we used one OPC Server for the PLC, one for the Vibration Monitoring System, and one for the Calculation Engine. Since the HMI, Process Historian, and the Machine Condition Monitor already supported OPC, we only needed three interfaces, which was one third of the previous total. Because OPC is a popular communication standard, the interfaces were available off-the-shelf, so no custom software development was needed.
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Notice that there is only one connection between each OPC server and its corresponding data source. When an OPC Server received three data read requests for the same point, it only had to send a single request to its data source. This drastically reduced the data request loads on each data source, to a third of the proprietary method, and significantly increased the performance for slow serial protocols such as Modbus.
The OPC solution only took 2 days to install and commission, at a cost of less than $10,000 for the software and associated services. The OPC solution helped the plant meet all of their requirements. It reduced data loads on each device, minimized implementation time and reduced their software acquisition costs. All of this was achieved with commercial off-the-shelf software.
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Module 3: Background Information The OPC Foundation and OPC Specifications OPC Foundation • • • • OPC Foundation is a non-profit organization Made up of hundreds of companies Interoperability sessions ensure OPC product intercommunication OPC Compliant products must pass OPC Compliancy test
The OPC Foundation is a non-profit international organization whose membership is made up of hundreds of companies throughout the world. It is responsible for establishing and maintaining the OPC specifications and strives to maintain interoperability.
OPC Interoperability sessions are held on a periodic basis around the world. During these sessions, vendors, who may also be competitors, send their technical experts to connect their OPC products with others. If they identify a connectivity problem, vendors can get together immediately to resolve the issue. This is all done in an effort to ensure that users have the best connectivity experience when they connect multi-vendor applications together. So check when your vendor last participated in an OPC Foundation Interoperability session.
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The OPC Foundation has also developed an OPC Compliance test suite. Those that successfully pass the test can submit their results to the OPC Foundation and display the OPC Compliance Logo on their product. The OPC compliance logo indicates that the OPC server complies with a particular OPC specification. However, the OPC Compliance logo does not mean that all OPC servers are the same. In fact, OPC servers can vary greatly in speed, reliability, capability and interoperability, which is partly why OPC Servers also vary greatly in price. So check with your vendor about the guarantees they offer.
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OPC Specifications OPC is a published industrial standard for the exchange of process control data and is available to anyone interested in developing their own OPC products. While there are many OPC specifications, here are some of the more common ones you will encounter: OPC Data Access, or OPC DA, provides access to real time process data. Using OPC DA, one can ask the OPC server for the most recent values of flows, pressures, levels, temperatures, densities, and more. OPC Historical Data Access, or OPC HDA, is used to retrieve and analyze historical process data, which is typically stored in a Process Data Archiver, database, or RTU. OPC Alarms and Events, or OPC A&E, is used to exchange process alarms and events. Operations personnel can use OPC A&E to notify them of alarms and obtain a sequence of events. OPC Data eXchange, or OPC DX, defines how OPC servers exchange data with other OPC servers. OPC Extensible Markup Language, better known as OPC XML, encapsulates process control data making it available across all operating systems. There are also other specifications such as OPC Batch and OPC Security. The OPC Foundation continues to update existing specifications such as OPC DA 2.0 to OPC DA 3.0. It is also working on new specifications like OPC for Complex data and OPC for ERP systems. So, as OPC evolves you can expect even more functionality in the future. It is important to select the correct OPC specification for your application. For example OPC DA and OPC HDA are separate specifications, and are used for different purposes. Furthermore, each OPC specification has a different release number such as OPC DA release 1, 2 and OPC DA release 3. Check with your vendor to find out the specifications and releases they support.
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Module 4: OPC DA Real-Time Data Access OPC DA Introduction • • • • OPC DA standardizes real-time data access Communication between all devices and applications is consistent OPC DA is available for every major process control system OPC DA secures scalability
OPC Data Access, or just OPC DA, provides a standard way to access real-time data from process control hardware and software. With OPC DA, the communication between all devices and applications is consistent. OPC DA servers for PLCs, DCSs, or other devices provide data in exactly the same format! Similarly, HMIs, Process Historians and other applications accept OPC data in the same format. This allows all of your process control hardware and software to freely exchange data, providing enterprise-wide interoperability. OPC is a powerful connectivity method. As a result, OPC servers are available for almost every major device and software application on the market today. Similarly, almost every process control application supports OPC in the form of an OPC Client connection.
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Major manufacturers have adopted OPC DA as their communication standard for the transfer of real-time data to secure their system scalability. Selecting OPC DA as your communication standard allows you to easily expand your system as needed for years to come. OPC DA began with OPC DA 1.0, followed shortly by OPC DA 1.0a. A later specification was OPC DA 2.0, with minor clarifications appearing periodically, such as OPC DA 2.01, 2.02, 2.03, etc. The most recent specification is OPC DA 3.0. Vendors are encouraged to keep their software current, so check with your vendor about the specific version that they support.
OPC DA Details • • • • Used only to read and write REAL-TIME data Provides access to single-value data items called “points” Each point includes a value, a quality and a timestamp Only uses latest values, not past values
OPC DA is used to read and write real-time data exclusively. To access previous, or historical values, you must use OPC HDA (Historical Data Access). Let’s consider a flow meter measuring the flow rate of a pump. In this example, the flow meter is connected to a PLC, which in turn exchanges data with an HMI client application.
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OPC DA provides access to single-value items, called points. For instance, a flow controller will have multiple points, including a set point (FIC101.SP), a process value (FIC101.PV) and others. OPC DA treats each of these as a separate point. Each point includes three attributes: a value, a quality, and a timestamp. OPC DA passes the value of the point, how reliable the reading is, and at what time the reading was taken, whether the point comes from a PLC, DCS or a software application. For example, a flow reading may have a value of “12.85 cubic feet per minute”, a quality of “good” and a timestamp of “October 7, 2003 9:15 and 17.358 seconds”. Typical questions posed by an OPC client and answered by an OPC server are “What is the current flow rate of FIC101?”, “Was this reading reliable?”, and “At what time was the latest flow read?”
OPC DA Timestamps • • • OPC servers provide a value, a quality and a timestamp If no device timestamp is available (e.g. Modbus), OPC servers provide a timestamp If a device timestamp is available, OPC servers pass it on
OPC DA servers provide three attributes for every point: a value, a quality and a timestamp. OPC specifies that a timestamp must be provided for each point, but it does not specify where the timestamp must come from. So where does the timestamp come from? Sometimes a timestamp is not available from the device. For example, Modbus does not provide a timestamp from the PLC. In this situation, the OPC server provides its own timestamp. But some device vendors do provide a timestamp with each value. So when the OPC server receives a reading, it also receives the timestamp from the PLC and passes it on. An OPC server may be designed to ignore a timestamp, even if one is available. Since OPC does not specify where the timestamp must come from, sometimes OPC server vendors choose to ignore the device timestamp because this takes less development effort. Always ask your vendor where their timestamp comes from.
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OPC DA Summary So to summarize, OPC DA provides standard access to real-time data and therefore provides open connectivity. OPC systems benefit from true interoperability and scalability that are used for monitoring and supervisory control. OPC enables applications to exchange, that is read and write, the latest values and not past values. If you need to access historical data, you must use OPC Historical Data Access (HDA).
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Module 5: OPC HDA Historical Data Access OPC HDA Introduction • • • OPC Historical Data Access (HDA) standardizes the exchange of archived data Historical Data is used for analysis: trending, fault prediction, root cause investigation, performance assessment, etc. Communication between all applications and data archives (Process Historians, RTUs, databases, etc) is consistent
OPC HDA, or Historical Data Access is used to exchange archived process data. To access realtime information you must use OPC Data Access, also known as OPC DA. Manufacturers around the world have been purchasing and implementing data-storage systems in mass numbers. These systems enable the usage of valuable data analysis tools. Using archived data, you can now accomplish trending, fault prediction, root cause investigation, performance assessment and other analysis from data that resides in almost any source. With OPC HDA, the exchange of historical data between an application and any data-archive is consistent. In other words, OPC HDA client applications that implement trends, reports, or spreadsheets, can retrieve archived process data from Process Historians, RTUs or databases in exactly the same manner. OPC HDA enables enterprise-wide interoperability because all applications that rely on historical data can finally rely on a single industrial standard that is supported by all the key vendors. OPC HDA Servers exist on the market today for every major process historian. Selecting OPC HDA as your communication standard enables you to access all of your archived data, providing true interoperability.
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OPC HDA Details • • • Any OPC HDA Client application can access archived data via OPC HDA Process Historians can answer queries relating to analysis OPC HDA separates the Process Historian from the client-side analysis application
Consider a flow meter measuring the flow rate of a pump. In this example, the flow meter is connected to a PLC, which in turn provides data to a process historian. Remember, the process historian is used to archive real-time data but once the data is captured, it can be retrieved using OPC HDA. In other words, the data can be accessed by any HDA client application such as data trenders, spreadsheets, and even reporting applications, in one consistent way by using OPC HDA. Typical questions asked by an HDA client application and answered by a Process Historian are: 1. What were the values of FIC101.PV over the past week, or 2. What was the average daily flow during the past Month, or even 3. What was the total monthly flow for each month in the past year? OPC HDA separates the process historian from the analysis tool. Imagine now that any application can connect to any data-archive. This enables users to change data archives and applications independently of each other.
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OPC HDA Versus Relational Data Standards Usage • OPC HDA - process data • ODBC/SQL – relational/business data • HDA and ODBC/SQL are complementary OPC HDA is a widespread standard to access historical process data. Other popular standards are SQL (sometimes pronounced sequel), or Structured Query Language, and ODBC, Open Database Connectivity. But, while OPC HDA is used for process data, SQL and ODBC are used for business, or relational data. It is important to note that the aim of OPC HDA is to access historical process data, and not business data. As such, OPC HDA and ODBC or SQL are not competing standards, but highly complementary ones. OPC HDA is an open standard that decouples archived data such as a process historian from HDA Client applications. Therefore, historical data can be exchanged freely between data archivers and analysis applications. Also, archived data and applications can be added and removed independently of each other so your system will have true interoperability from the beginning.
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Module 6: Additional Resources Matrikon Advantage and free downloads Matrikon is the world's largest OPC developer. We provide connectivity to every major control system and application on the market, with a collection of over 500 interfaces. Our vendor interoperability and OPC compliance are guaranteed. So far, we have attracted over 30,000 users and 100,000 installations around the world. Whether you need real-time process control data, historical trends, or even the transfer of events, OPC is an excellent standard for your data exchange requirements. With OPC, you can use multi-vendor solutions that provide true interoperability, and create a best-of-breed solution. This helps to reduce the total project integration time and costs, while providing a scalable system that can be easily modified in the future. I encourage you learn more about OPC. For example what affect OPC has on data transfer rates, how OPC works with SCADA applications, dealing with networking issues, implementing redundancy and other topics. For more information visit the OPC Foundation website or the Matrikon website. Or just click the “additional resources” link below. There you can sign up to attend a live OPC webinar, download and evaluate OPC tools and drivers, read a variety of OPC whitepapers and learn more about what it takes to implement OPC. Or simply contact us so we can answer any questions you may have. Website: Visit the www.matrikon.com/opc for additional OPC resources, current news and products Webinars: Sign-up to attend an online OPC information session at www.matrikon.com OPC Newsletter: Subscribe to Konnections, a regular and current source of OPC news and information at www.matrikon.com OPC Drivers & Tools: Browse the list of OPC server and client tools available at www.matrikon.com/opc Share this Presentation: Invite a friend or collegue to view this presentation Comments & Questions: Provide feedback, tell us about your project or request to speak to an OPC product specialist. See contact information below.
Inquiries or to request a copy of the OPC Online Tutorial on CD: Matrikon 1800, 10405 Jasper Avenue Edmonton, Alberta, Canada T5J 3N4 Telephone: 1-780-448-1010 Fax: 1-780-448-9191 E-mail: opcinfo@matrikon.com Website: www.matrikon.com
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