Products > Dodgy Technology

Cable validator

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Raj:
So I saw this video from Linus tech tips-
https://youtu.be/u6lx1ntNoxE?t=88
I thought, cable testing just needed a continuity tester (be it modded to beep when continuity is broken) and sockets (to actually get access electrically, of the pins of the connector) as long as you have the cable, well under standard maximum supported length.
Sure, you can have fixtures for a factory environment but expensive oscilloscopes? for digital signal? simple lcr meter ain't enough?

Kleinstein:
For really demanding cables one may actually need quite some effort to really test a cable all the way to the details. The box does not look really dodgy, though may be already at the limits with HDMI.
The video however looks a bit odd - for me the way the video is made rings some alarm bells and makes me a bit suspecious.

TimFox:
I haven't viewed the video, but there are cable faults that will not be measurable with continuity or LCR meter.
The usual test equipment required for some types of faults is "TDR" for time-domain reflectometry.
For example, back in WW II, it was noticed that the manufacturing process for coaxial cable could produce a periodic deviation in the dielectric diameter along the cable length, which would result in interesting interference effects at certain frequencies where a small reflection at each cycle of the deviation could add up to serious problems for a long cable.

Kleinstein:
The cable tester seems to measure the eye diagrams, which is standard for testing transmission systems. However a large part of the error is usually from the send and receive side and more like an amplifier if present. The cable is only one part. The more tricky part could be the connectors and here half of them are in the tester, with additional one for the front ends.

Raj:

--- Quote from: TimFox on October 14, 2021, 08:26:55 pm ---I haven't viewed the video, but there are cable faults that will not be measurable with continuity or LCR meter.
The usual test equipment required for some types of faults is "TDR" for time-domain reflectometry.
For example, back in WW II, it was noticed that the manufacturing process for coaxial cable could produce a periodic deviation in the dielectric diameter along the cable length, which would result in interesting interference effects at certain frequencies where a small reflection at each cycle of the deviation could add up to serious problems for a long cable.

--- End quote ---
aren't those for RF? I do know the phenomena of line ringing and importance of termination of coax so they are indeed more complex than twisted pairs and straight lines that are generally used in HDMI, ethernets and USB.

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