On Thu, 20 Jan 2022 14:19:17 -0800 (PST), Tom Kunich
Nobody asked you to design a PWM cable tester. Since you claim that
it exists, I asked you to find me one or describe how it works.
>and waste any more time on you.
I forgot about that. You promised not to respond to the "haters".
That would be me. I hate you. So, why are you responding?
>You aren't even a technician and you're telling an engineer
>that he doesn't know what he's talking about.
You are not an engineer. You may have written firmware and worked
with engineers on various products, but that does not make you an
engineer. Whether you are or are not an engineer doesn't matter. You
still don't know what you're talking about.
>If you had ANY reputable experience at all you could at least
>understand how that would work.
I already declared that I have no knowledge, experience or familiarity
with a PWM cable tester. Please display your vast knowledge and
enlighten me as to how such a device might operate.
>You and Jeff can agree with each other than you can in some
>manner use a megger to check a mile of wire for shorts or opens.
You didn't read what I scribbled. A Megger (high voltage dielectric
and insulation leakage tester, only tests one of the numerous
specifications required for a cable to be acceptable. Nobody
mentioned using one for a continuity tester by just checking for
shorts or opens. I can do that with a common multimeter.
>After he cites Time Domaine Reflectometry which is really
>what I was speaking of since it CAN use PWM to give additional
>information,
What additional information will PWM provide in time domain
reflectometry? Are you aware that the TDR only uses the leading edge
of the pulse and generally ignores the rest of the waveform? The
pulse can be as narrow as you want (within rise time limitations) or
as wide as you want (within power consumption limitations), and the
TDR will display much the same information. What additional
information do you believe it can provide?
>Even
>in that Fluke comment it describes modification of waveforms due
>to signal input and cable length but stupid doesn't understand
>anything that means.
The comment was:
I don't see anything describing "modification of waveforms due to
signal input and cable length" in the comment. The article describes
problems that might occur in a VFD (variable frequency drive) where
the fast rise time (needed to reduce power consumption), and long
cables, can cause a (power) transmission line impedance mismatch,
which produces high voltage overshoots, which might blow something up.
The PWM signal to a VFD is modulated to create a sine wave and change
the speed and direction of an attached motor:
<
https://www.kebamerica.com/blog/pulse-width-modulation-in-vfds/>
None of this has any application to *TESTING* a cable.
>...can't even understand that you use PWM
>to achieve Time Domaine Reflectometry since that pulse width of
>necessity changes with the length and other particulars of the wires
>being tested.
It would seem that you are doing a credible job of demonstrating that
you don't understand how a TDR works and how it's used.
Which functions and on what page does it show how to test a cable with
PWM? I couldn't find anything that mentions PWM.
BTW, the article is really basic and covers what a lineman needs to
know about how a TDR works for testing power lines. After all, that's
the business of the vendor who posted the article on their site.
Also, it's bad enough when you don't bother to substantiate your
claims with references and links. It's worse when you waste my time
with unrelated URL's and references that have nothing to do with the
discussion.
Stand and deliver. I want to know how to use PWM to test cables, and
I want it now or post a retraction.
[ I can't believe I wasted 60 mins on this ]