Controllers: Software is difference between PACs, PLCs

03/15/2007


Controllers, PLCs, software, PC-based control, embedded control

LabView SignalExpress from National Instruments is an out-of-the-box, ready-to-run data logging tool with easy-to-use, drag-and-drop capabilities for controlling hundreds of measurement devices.

Programmable Automation Controllers (PACs)—devices that combine the functionality of a PC with the reliability of a PLC—are increasingly incorporated into control systems. Software is a key difference between PACs and PLCs, and a recent white paper from National Instruments (NI) explores this topic, as well as the direction NI sees industrial control taking with PACs.

The acronym PAC, coined by ARC (Automation Research Corp.), is typically used by traditional PLC vendors to describe their high-end systems and by PC control companies to describe their industrial control platforms. According to NI, engineers solve 80% of industrial applications with traditional tools, which creates strong demand for simple, low-cost PLCs. That leaves 20% of the applications to be built by engineers who require higher loop rates, advanced control algorithms, more analog capabilities, and better integration with the enterprise network. PCs solved some of those problems. Essentially, they provided software capabilities to perform advanced tasks, but they still were not ideal for control applications.

As a result, says NI, engineers with complex applications worked closely with control vendors to develop new products that would combine the advanced software capabilities of the PC with the reliability of the PLC. The result was the PAC, named by ARC in its 'Programmable Logic Controllers Worldwide Outlook' study.

Software is the key difference between PACs and PLCs, says NI, with two camps typically emerging: software providers with a PLC-control background and those with a PC-control background. With its background in measurements, NI is extending the PAC concept beyond simple I/O systems by incorporating higher-speed measurements and machine-vision capabilities. It notes the future for PACs hinges on the incorporation of embedded technology and the ability to use software to define hardware.

NI offers five LabView-based PAC platforms. Read about the NI offerings and more about PACs overall in the complete whitepaper, PACs for industrial control , the future of control, in the Control Engineering Resource Center .

LabView Signal Express
In separate, but related product news from NI, the company is extending its LabView graphical system design platform with the release of NI LabView SignalExpress, interactive measurement software that simplifies data logging, instrument control, and academic instruction. The product lets engineers and scientists quickly acquire live measurements, log data to a disk, and export the data to a spreadsheet application, such as Microsoft Excel. The software is fully integrated with more than 250 data acquisition devices, including the NI CompactDAQ modular data acquisition system. Engineers can easily control more than 400 modular and stand-alone instruments and automate the acquisition, analysis and storage of data.

In addition, NI has added 19 new I/O modules and LabView SignalExpress to its CompactDAQ Platform The new modules further expand the measurement and control capabilities of the portable, rugged, USB-based data acquisition system, adding measurement options such as RTD; current I/O; high-density digital I/O; high-speed, 24-bit precision analog; and channel-to-channel isolation. Every CompactDAQ chassis is shipped with LabView SignalExpress LE.

Advances in NI Multisim and the NI Circuit Design Suite 10.0 platform have also been made. The NI Circuit Design Suite 10.0 platform, which combines Multisim and Ultiboard with NI measurement software such as LabView SignalExpress, requires virtually no programming and helps engineers integrate design and test functions. Version 10.0 introduces several design features focusing on advanced simulation tools and new MCU cosimulation, increased quality and breadth of the component database, and strengthened design community and industry partnerships.

Learn more about these new products on the National Instruments Website .

—Edited by Jeanine Katzel , senior editor, Control Engineering





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