Ancestors

Written by Electronic Eel on 2024-02-29 at 17:00

Was at the EMC test lab for work today - and I guess I've got a bunch of extra work ahead 🥴​

This is conducted emissions on the ethernet port. The device needs to meet category B, so the lower two lines are the limit...

[#]electronics #emc #emi #emissions

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Toot

Written by Electronic Eel on 2024-03-19 at 20:38

You may remember my post about the completely failed EMC test from about 3 weeks ago - I finally got proof of what the issue was: the EMC test lab bodged the test method and didn't ensure proper impedance on the measured cable.

The two attached graphs are from the same device, but just one measurement is done properly...

[#]electronics #emc #emi #emissions

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Descendants

Written by Electronic Eel on 2024-03-19 at 20:39

The last 2 weeks I tried & failed to reproduce the measurements done by the EMC lab. I upgraded my test equipment at work to no avail and began to doubt my understanding of the matter.

Then it dawned on me that the impedance on the measured line isn't something they could calibrate for all different customer DUTs, so it should have been measured, and this was something they didn't do back then. Then it was a bit of back and forth convicing them of their error, but in the end they agreed to redo the measurement.

For the readers deeper into this topic: this is conducted emissions on a ethernet network cable, measured according to C.4.1.6.3 of EN 55032. They didn't measure impedance per C.4.1.7 and the ferrite they used between the 150 Ohms resistor and the auxiliary equipment (AE) wasn't good enough, resulting in much too low total impedance.

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Written by jacquelines 🌟 on 2024-03-19 at 21:06

@electronic_eel hell. congrats on working it out!!

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Written by sky-guided on 2024-03-19 at 23:49

@electronic_eel they gonna bill you for that?

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Written by Electronic Eel on 2024-03-20 at 06:45

@skyguided no, they don't bill me for redoing the measurement.

But it costed me many hours figuring out what the problem was and that they caused it. Would love to be billing them for it - but that would require some fighting I don't have the time or energy for.

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