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“Documentation is my pet issue,” he says. “The first things students hear—and they face it throughout the class—is that the whole concept of this technology brings with it a need for excellent document control. You better have a handle on where the wire is, what switch it’s going to, and whether the switch is managed.” Control engineers are not going it alone. Carter has seen an ever-increasing number of IT engineers in attendance, and often finds them excited about applying the principles of control to Ethernets. We suspect some of the control engineers might be learning more about IT than they ever wanted to know.
Train a Trustworthy Installer
Industrial networks—especially at the transport, network, and application layers—certainly are complex, but when installation and maintenance issues crop up, the real problems usually are down at Layer one—the physical layer, which for the most part, concerns basic wiring principles.
Helge Hornis, Pepperl+Fuchs’ intelligent systems manager, says roughly 95% of the service calls P+F receives about the AS-I bus P+F supports are wire-related—not equipment, not software.
“The biggest issue that I’ve seen with industrial networks—especially DeviceNet and ControlNet—is in the media installation, and especially with DeviceNet,” observes Chris Wahl, controls engineer at Stone Technologies, a system integrator based in St. Louis. “The media installation has to be done by an electrician you really trust.” Maybe keeping a couple of well-trained, certified installers in house is a good idea.
Mark Llewellyn, electrical controls engineer, Navistar International, sent a couple of people for Profibus training, and then used them to train the remainder of applicable personnel in his factory.
When fiberoptic media is required, Polytron’s Persyn recommends technicians with specialty certification to terminate fiberoptic connections. Cat5 connections to a patch panel or RJ45 connectors are somewhat simpler but do require special punch down and crimping tools. He typically details the connections on the drawings.
Control Technology Inc. designs and builds factory automation solutions with expertise in high-performance analog and plant-floor communications—specifically Ethernet TCP/IP, Profibus-DP, and DeviceNet. They know training is vital in many areas. “We have two engineers that have attended the PTO ‘Certified Profibus Network Engineer’ training,” says Fred Wilson, applications engineer. “It focuses mainly on installation and debug of Profibus networks. It is useful in developing product specifications and customer support situations, but it is not a requirement for design engineers.” A one-day course discusses protocols, configuration tools, and installation requirements.
“I have been badgering the Fieldbus Foundation and the organizations that test fieldbus devices and issue their “check-marks” to institute certification programs for wiring installers, “ states Maris Graube, president of network testgear provider Relcom. “I believe this would weed out Bubba and Skeeter who have just slapped a magnetic sign on the side of their pickup truck that proclaims them to be wiring installers.”
A valuable learning resource is a network certification lab. Phil Lewis, Schneider Telemecanique Automation & Control Services network specialist and field service engineer, says the ability to mock up a factory environment in a certification lab is invaluable training that can save considerable integration time and money. “Such a lab could replicate the loading that would be seen in the target environment and simulate fault conditions so [these] effects can be designed out before deployment,” says Lewis. He adds that the lab also is useful after installation to simulate fault conditions that are seen during operations, and allow engineers to correct the problems.
Many vendors offer labs to do these mock-ups, so it’s a good idea to check with them before setting up an installation you’re still not sure about. In addition, specialized tools may be required for configuration; for example, Wilson uses a Profibus configuration/parameterization tool called COM-Profibus.
Whether it’s troubleshooting a just-installed network, prior to commissioning it, or maintaining a network down the road, there are some basic tools you can’t do without. “The best tool for troubleshooting our network,” says Navistar’s Llewellyn, “is a good solid schematic. All the software and hardware in the world can’t get you any closer to the solution if you have no idea how the network is laid out. For example, Profibus has terminating resistors integral to the terminal connectors. By understanding how these terminating resistors are placed in the network, you can find the problems. Without a good road map, you are just hunting for Easter eggs until you stumble upon the answer.”
|FIGURE 2: SHARP TOOLS|
A handheld network tester interfaces to a PC over a USB port so that key network variables can be measured and put into the computer for historical recording and report generation. Source: Relcom
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