My dependable generic two-piece network cable tester finally released its magic smoke after roughly 15 years and well over 2,000 cable tests. It has the usual eight indicator lights, an on/off switch, a 9V battery, and RJ45/RJ11 ports. I accidentally connected it to a 60W PoE++ injector after checking a cable. I assumed the injector would negotiate first and refuse to provide power to a device that could not respond, but apparently that was an expensive assumption. The tester survived years of exposure to various passive and active PoE equipment, but not this injector. Should I simply buy another inexpensive continuity tester, or is there a reasonably priced, more capable cable tester that can handle PoE safely and provide useful diagnostics?
4 Answers
Even inexpensive testers can offer more than a simple continuity check. Some include basic TDR measurements and show the approximate length of each pair, which can reveal a damaged or poorly made cable when all eight conductors appear correctly wired. It still will not replace a proper verifier or certify bandwidth, but it is a useful upgrade without the cost of a premium Fluke unit.
Be careful assuming every injector negotiates properly. Compliant active PoE uses detection and classification before applying power, but passive and vendor-specific implementations can put voltage on the cable without a normal negotiation step. Cheap or unusual injectors are especially risky, and high-power versions can damage anything connected to the far end that is not designed for it.
A basic continuity tester is useful for checking wiring order, but it will not prove that a cable can actually carry Ethernet traffic or handle PoE. A proper verifier can test link speed, PoE behavior, cable length, pair faults, and sometimes provide TDR or performance reports. Fluke and NetAlly tools are excellent, though the higher-end models can be difficult to justify on a personal or departmental budget.
The high-end models look fantastic, but getting approval for a purchase costing several thousand dollars is going to be the harder test.
For something more affordable, the Klein Scout Pro Max is a solid step up from the basic eight-light testers. There are also older Fluke or NetAlly units available at lower prices, such as the AT-series testers. They cost more, but they make troubleshooting much faster and are designed for real network and PoE work.
I recently started using a higher-end tester nearly every day, and the time saved compared with a generic continuity tester has been noticeable.
This was a 60W Ubiquiti injector, so I expected it to behave more politely instead of applying power before establishing what was connected.