As always, these testers (the affordable ones) are capable of testing continuity, and, I guess, the cable chip report.
If you want to test bandwidth, that's a five- or six-figure bit of gear.
If you want to test bandwidth, that's a five- or six-figure bit of gear.
Resistance measurements can cursorily test claims of 240W but resistance changes with temperature which changes with current...so unless your tester puts 5 amps down the wire for 5 minutes and then tests resistance it's not a very good test.
For home use I've ended up treating real capability as an empirical property of the specific cable+port+device combo: does this exact cable drive this monitor at the mode I want, under load, for an hour? If yes, it gets a colored heat-shrink band and never leaves that use case. Everything else is a phone/charge cable until proven otherwise.
You need to generate a precise, calibrated, 40GHz signal, transmit it, then precisely measure the returned signal for phase, amplitude, and waveform integrity -at that speed.
Oscilloscopes and logic analyzers that run at that speed, are damn expensive.
You need to at least look at waveform integrity (which can be approximated, by doing things like looking for harmonics).
For example, you may send in a 40 GHz square wave, and get back a wave full of ringing, or a sine or sawtooth wave. It’s damn difficult to maintain clean square waves, at that frequency. The cable could also double as a microwave antenna.
Since it’s digital information, some waveform alterations are OK, but not too much. You need fairly clear state transitions. Ringing, or waveform distortion, can introduce extra (or fewer) transitions; thus, completely changing the data.
E.g., here's what a bad connector at the far end of an SFF-8654 cable looks like on a TDR: https://i.imgur.com/AiLnSuC.jpeg . This type of plot can be interpreted as impedance versus distance along the line. It could be made with a small handheld instrument, but currently a human is needed to read the tea leaves. While I was making that measurement, I couldn't help thinking that it would be nice if it didn't require either a 50 GHz VNA or equally-expensive training to read.
Equivalent-time sampling gets you out of needing an expensive network analyzer, but it doesn't help with the diagnosis itself. And of course when checking a USB cable you are most likely just after a go/no-go result, not the gory details. That further calls the market economics of such a gadget into question. Still, if somebody offered one at a reasonable price, they'd sell at least one to me.
As long as we don't get false positives. They are worse than false negatives, and is what happens, when you just read the markers from the chip. As we know well, lots of dodgy C.M.O.T. Dibbler-types will deliberately program the chips to emit bogus markers.
Because that is not reproducible and introduces all sorts of other random variables to your test.
Expensive equipment is the only answer here.
Its a bit like when you ask an electrician to install network cable (yuk !).
They consider their job done after a continuity test (if they bother to do a continuity test at all).
Meanwhile, if you put a Fluke on it, you will pick up all sorts of subtle faults that the electrician's continuity tester will never pick up, but will cause subtle and hard-to-diagnose problems when you try to push data over the cable.
Its the same thing with all those cheap USB testers.
They might have all sorts of fancy displays, but in the end they are no substitute for the real thing and will end up lulling you into a false sense of security.
Actually no. That one is no good.
The one I had in mind is the one that professional network cabling installers use.
This one: https://www.cdw.com/product/fluke-dsx-cableanalyzer-dsx2-500...
Only $13,000
:)
Datasheet: https://www.flukenetworks.com/datacom-cabling/Versiv/dsx-cab...
Your link 404's for me, here's it on Amazon.
Note: not an affiliate link but if I had one I'd totally use it here ;)
Dedicated test equipment that can reliably and verifiably test these high speeds is niche and therefor expensive. There's not really a way around that issue.
Make some properly formatted garbage, send it down the wire to the other end of the tester and see if you can read the result. It won't tell you if the cable is marginal, but how often is that actually an issue? Network cables are connected to hardware that retries, masking such errors.
A device isn't even necessarily better if it works with one cable when another doesn't, it might just happen to have a slightly lower impedance on its internal traces that happens to better match an out of spec cable, or any other one of a number of parameters.
I throw out every usb cable that comes bundled with devices because they are literal junk.