Maintaining connections

There are plenty of issues that cause network headaches, but never assume your electrical subcontractor is familiar with routing and terminating network connector cables, even if they do it all the time.

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Fiber Methods

A fiberoptic installation normally requires field terminations. Here are some tips your installer should know:

  • See if an anaerobic connector system will work for your application. If so, you can skip the curing oven and eliminate one more source of error.
  • Understand that “feel” is important when inserting the fiber into the connector. You can develop feel by setting up a practice station and doing several test runs on spare cable and connectors, and evaluating the results. This also is true for the polishing.
  • Set aside the notion that “if a little is good, then more is better” when using the epoxy. Too much is just as bad as not enough. Follow specifications precisely.
  • Use a microscope to inspect the polished connector. The flaws you don’t catch with the unaided eye will degrade the system.
  • Use a fiberoptic test set. Don’t rely on visual inspection alone, which can evaluate only the surface finish of the fiber. Other defects such as micro-bending or fiber breaks inside the connector need correction, too.
  • Obviously, dirt interferes with fiber signal transmission. But so can ordinary condensation, chemical cleaners, and solvents. When planning your fiberoptic system, ask connector providers about protection methods. Note that some methods make it difficult to undo a connection. Look for an industrial-grade optical connector with an IP67-rated seal.

Connector Styles

These are the more common connector styles used in networks:

  • Mini connectors have a 0.875-in (about 23 mm) barrel and 16 threads per inch. They have two to seven pins. Best application: Where space is at a premium and cables are thin.
  • Micro connectors are smaller than mini connectors, and follow European standards: They have a 14-mm (0.55 in) barrel and use M12 threads. Typically, they have two to six pins, but an M12 connector might have up to 12 pins. Best application: Where the equipment being connected adheres to metric standards rather than SAE. Also useful for two-pair Ethernet.
  • DB connectors come in a variety of sizes. Most common are DB-9, DB-15, DB-19, DB-25, DB-37, and DB-50. The number after the DB indicates the number of active lines the connector has, and not the number of pins. Network applications typically use a nine-pin DB-9 connector. Most computer monitors have a DB-9 connector. Best application: Serial connections. They’re commonly used for “snap-on” connectors, rather than plug-in or threaded.
  • IP67 RJ45 connectors are an industrialized version of the ubiquitous RJ45 connector, the most common Ethernet connector. Two problems with RJ45 are the small contact size and the weak clips—neither of which were originally intended for industrial use. Best application: Where standardizing factory floor Ethernet with the office Ethernet is desirable and failure is tolerable.
  • Narrow-tongue compression lugs provide high-quality, safe, reliable terminations, if you have the correct die for a given connector. Best application: Accommodating limited-space applications where you want lug-style connections.
  • Pluggable connectors for I/O modules simplify installation, speed up maintenance, and reduce wiring errors. Common features include built-in test points, tool-free operation, integrated coding, and industrial-grade (vibration-resistant or vibration-proof, thermal cycling resistant, and corrosion-resistant) secure mechanical connection. Best application: Reduce construction time via pre-manufactured wiring harnesses (in house or outsourced), or to simplify replacement of I/O modules.

Custom cable/connector assemblies (made at the factory or by a specialty shop) allow elimination of tedious connector assembly in the field, where it’s tougher to get right. This can result in serious cost-savings up-front, plus increased reliability for the life of the installation. Consider this for projects that you can plan in sufficient detail to know the needed cable lengths and which connectors to use with each one.

Custom connectors with modular inserts can solve oddball problems. Depending on the scope of your project, you might find it cost-effective to “mix and match” the housing of one connector with the guts of another rather than doing a major redesign.


  About the Author
Mark LamendolaMark Lamendola is a frequent contributor to Control Design and Industrial Networking, with many years of experience working on and writing about industrial automation issues. You can reach Mark at comments@mindconnection.com.

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