Design News, February 2013

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Each Expansion & Powerful Programming Tools PACs offer extensive built-in functionality, and they also have a modular design that simplifies system changes and expansion, making it easy to add up to thousands of I/O points. By contrast, a typical PLC is designed to control much smaller systems, with high I/O counts often impractical because of performance degradation. Multiple PAC programming languages offer flexibility and easy scalability for larger systems. In particular, most PACs offer tag-based naming conventions. This means programming system changes in a PAC doesn't involve the complex re-engineering to make such changes in an average PLC. With a PAC, a single tag-name database is shared across all development tools, thus requiring only one software package for programming. Each tag can consist of a descriptive English syntax name, and can be assigned to specific functions before tying to a particular I/O or memory address.This means variable names no longer must function as both a name and description.Where previously names consisted of numbers or arcane expressions such as "bits(3).5," easy-to-understand terms such as "Tank 1 High Level" can instead be used. Built-In Capabilities Reduce Costs Overall, PACs provide greater flexibility in programming, larger memory capacity, better interoperability, and more features and functions than a PLC, all at less cost than a DCS. A PAC is also easier to implement than a DCS, and is more scalable for lower I/O count applications. With an I/O capacity in the hundreds of thousands, extensive built-in memory, and powerful processing capability — a single PAC can be used to monitor and control large systems encompassing several areas of a plant or an entire facility. In addition to monitoring and controlling large areas of a plant, a PAC reduces costs by simplifying the communication of data between the plant floor and higher level computing applications and systems.The built-in communication capabilities of a PAC often negate the need to invest in middleware, extra gateways, and components — as the standard protocols and networking ports in a PAC make it easy to communicate with SQL databases, ERP systems, asset management systems, and enterprise-wide historians. DN For More Information: AutomationDirect: WASHERS & STAMPINGS POWER TRANSMISSION-PART CONVEYING PYRATHANE® BELTS With Lifetime Warranty Against Manufacturing Defects Very Clean in Operation Eliminates Tensioning Devices Exceptional Abrasion Resistance COLORS AVAILABLE FREE CATALOG & BROCHURE CUSTOM MADE IN INCH, METRIC & O-RING SIZES Round, Flat and Connectable Polyurethane Belts Samples available at little or no cost. DIAMETAPE BELT MEASURING TOOL Allows for accurate, non destructive measurements on o-ring and belt inside diameter (ID) or inside circumference (IC). Available in Standard and Metric Sizes. Call 1-888-WASHERS 1-888-927-4377 • 612-729-9365 • FAX 612-729-8910 AN ISO 9001 CERTIFIED COMPANY (P) 641.792.2405 • E-mail: WWW.BOKERS.COM/DN 522 North Ninth Avenue East, Newton, IA 50208 Design News | february 2013 | www.d esign n –53–

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