Plant Services - October 2007 - (Page 52)

PERFORMANCE Automation But will wireless work in your application? In many cases, you can’t tell at a glance. Those pine trees might interfere with a signal. The wireless signal might not be able to pass through that building. Your area might have too much electrical noise, excessive inter- ference or conflicting signals. One solution some wireless vendors offer is a detailed engineering analysis, involving coordinates, site maps, topographical maps, and so on. Another more empirical way to evaluate suitability is to take a demo system to the plant and try it out. Surveying sites When plant professionals ask if wireless will work in their plant, we’ve learned that blanket statements or hurried assurances are inadequate responses. Instead, you should consider doing a site survey to find out for sure. This involves mounting a transmitter and an antenna at remote sites and an antenna and receiver at the controller site in a point-to-point configuration (Figure 1). Then, fire it up and see if it works. The radio’s onboard diagnostics quantify the signal strength on each hopping frequency the radios use to transmit data. This also helps to determine if any portion of the spectrum is subject to interference from co-located radio systems or cell towers. If so, the final wireless system can be programmed to ignore the “noisy” portions of the spectrum. A steel mill, for example, had been using a manual system to collect flow meter data. Essentially, an employee toted a clipboard during routine visits to eight flow transmitter locations. The mill asked if a wireless system could reduce this labor and was pleased to learn that an omnidirectional antenna could transmit to and receive signals from the eight flow transmitter locations. With the concept proven, the plant installed a wireless link module for an Ethernet network radio system and an Ethernet interface module with control software that enabled the distributed control system to do the flow totalization at each flow transmitter. A wireless link module in the computer room on the process floor set up in a point-to-multipoint configuration served as a multipoint master that received data from eight transmitters (Figure 2). This hardware combination provided a reliable and versatile alternative to the mill’s inefficient use of labor. At the same time, the system provides continuous access to the process data. October 2007 52 www.PLANTSERVICES.com http://v1000.yaskawa.com http://v1000.yaskawa.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - October 2007

Plant Services - October 2007 Contents Monetize It Letters Step into the Blogosphere What it Takes to be a Leader Up and Running Crisis Corner What Works From the Summit Treat Them Right Access Control Out of the Woods Show Me, Don't Guess Condition Assessment Made Easy The Air Above the Floor Power to the Prime Movers In the Trenches Illuminating Maintenance

Plant Services - October 2007

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