The idea of Supervisory Control and Data Acquisition (Scada) systems dates back to the 1970s when minicomputer-based telemetry systems were deployed to look after oil pipelines and widely distributed remote assets of water and power industry resources.
The term Scada was first applied in the mid 1990s to a new class of PC-based software systems that had emerged following the introduction of the personal computer in the early 1980s.
Convinced that the PC would replace traditional control equipment such as programmable controllers and multiple loop process controllers, the early enthusiasts pitched their products as combination controller and human-machine interface (HMI) packages. They were largely defeated by a combination of the PC’s shaky, slow performance and the efforts of the traditional control manufacturers, who staunchly defended their markets with improved controllers and fast, inexpensive HMIs.
By the time of the mid 1990s, the climate for industrial PC packages had progressed. Faster Pentium processors combined with the much easier to use Windows operating system made PCs more attractive, and the increased use of Ethernet on the factory floor made connecting to third party equipment less complicated. Even some Windows-based industrial standards, such as OPC (OLE for Process Control) had begun to emerge, which would help bridge the gap between PCs and the control equipment they wanted to supervise.
On the other hand, several factors worked against the idea of bringing the PC into the factory. First, the PC Scada packages were far too expensive for what they actually delivered. The moniker Scada was itself inappropriate-the packages almost never did any control, supervisory or otherwise; they were in effect just overpriced software used to gather and monitor data. Newer, more powerful PLCs could provide that functionality, and moreover, a number of new software packages called Manufacturing Execution Systems (MES) had already started to show that they could connect with industrial control equipment and deliver useful information to factory managers. So what was Scada really needed for?
The drive for information
Manufacturing in the 21st century has become an information-intensive activity, more so than in any past generation. Several reasons have caused this to happen.
First, manufacturers face severe competition on a global scale, and must use extra resources to improve the quality and delivery of their products. Secondly, manufacturing has transformed from mass production to what is now called 'mass customisation' where companies produce a greater variety of products built to customers' specifications.
This requires more flexibility in the production, assembly, and packaging of manufactured goods. And thirdly, government regulation has required manufacturers in the pharmaceutical and food and beverage industries to acquire and store massive amounts of data on the products they produce, and this type of burden is increasingly shared by other industries who must protect themselves from the possibility of litigation as the result of faulty products.
Government environmental regulations add to the need to monitor and store both production and effluent data.
Thus, the need to acquire, monitor, and share information in the manufacturing process has grown to a large extent, and can only be satisfied with computer based data acquisition systems. PC-based Scada systems, tightly coupled to the manufacturing control systems, are in the best position to not only acquire massive amounts of data, but to sort it out and deliver the appropriate information to the right people. Scada systems have become the information gateway between the factory floor and higher-level business systems.
Thoroughly modern Scada
COPA-DATA’s zenOn system is built on an object-orientated platform that satisfies the needs of PC-based Scada systems for contemporary manufacturing. Great care has been taken to lessen the burden on engineering resources and to make the system easy to install, even for very large and complex applications. By using dynamic objects-which can be cloned indefinitely, a big help in constructing large systems-and linking them together in a way analogous to Microsoft Windows, a change in the ‘master’ object automatically changes all linked objects in the system.
For greater speed and efficiency, the network uses event-driven broadcast techniques instead of time-consuming polling; this keeps all the stations updated in real time.
Network-based decentralisation means that any PC in the system can be a client or a server. The software is compatible with any topology, but a ring topology is favoured and typically used to ensure redundancy. With circular redundancy, a backup server continually ‘shadows’ all communication, and in case of failure, resumes operation with no loss of data. This guarantees there is never any downtime.
Portable computing has become important for engineers and technicians who must cover wide areas in manufacturing plants. ZenOn was designed to be mobile from the outset, and its WindowsCE version that runs on a PDA is fully compatible with the WindowsXP and Server2003 versions. COPA-DATA, after Siemens, sells more WindowsCElicenses than any other industrial software provider.
OPC has become the industry standard for linking various manufacturers’ devices together, and zenOn provides this capability. However, to ensure maximum performance and device compatibility, zenOn software engineers have gone beyond OPC to create their own software drivers that take full advantage of a device’s functionality.
Thomas Pubzenberger is MD of COPA-DATA. For more information, www.copadata.com"