high impedance capacitive cable, what is it

hello, I heard somebody talking about a type of cable the other day and I can't find any information on it... does this make sense to anybody:

I was doing a continuity check (aka ohming out, ringing out...etc etc) on a db15 cable with all the pins connected straight through the cable... and my multimeter was showing very high (open) resistance on all the pins... then someone said something that was something like this:

"maybe it's a capacitive type cable where it sends/recieves pulses.... then it would make sense that you're seeing such high resistance"

- I've tried googling to find out what this person was talking about, but have found anything.... I was wondering if anyone in here knew what this person may have been talking about?

Thanks, Fibo

Reply to
Fibo
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Ignore the capacitive cable comment. There's no such thing. Those fast edges would experience all kinds of frequency dependent delay and the cable would not have a constant characteristic impedance to support signal integrity.

Are you sure your meter leads are OK? Are the pins (or leads) corroded or oxidized?

Steve

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Reply to
Steve

All metalic cables, connectors and conductors have low ohmic resistance regardless of their impedance. If you do not have low ohm continuity, something is wrong, pin confusion, broken wires, un-crimped pins, corroded pins, mis-wired, bad meter, etc.

Reply to
Bob Eld

ges

ld

Yeah, my cable and meter are fine... my cable is just a regular cable, I haven't opened her up yet, but I imagine there's nothing connected in it... but that's no problem... my real confusion/question was.... trying to figure out what this person was talking about... because I've never heard of anything like that... a capacitance based cable that's used for transmitting pulses and uses regular DB9 (or 15 or whatever) type of connectors.... I was just wondering if that made sense to anyone in here...

Reply to
Fibo

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He was talking nonsense.

Some of the possibilities are:
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Reply to
John Fields

ok... good... so there's no pulse sensing type of cable that wouldn't register a low impedance.... I'm glad to hear that, cause I didn't know what in the world he was referring to

much thanks

Reply to
Fibo

The only cable I have ever seen where I got odd results, turned out to be thermo-couple cable. The 2 conductors are made from different metals. I did not know what it was and used it for my supply. My circuit did not work, and it turned out I had quite a big voltage drop over a fairly short piece of this cable.

Regards Anton Erasmus

Reply to
Anton Erasmus

Hi Fibo

Could he have meant something like this?:

Fluke PM9080/001 *Optically* *Isolated* RS232 Adapter/Cable:

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/Glenn

Reply to
Glenn Møller-Holst

Stupid answer.

Reply to
Robert Baer

Check; most likely connection problems between meter leads and cable connector(s).

Reply to
Robert Baer

No such thing, and zero reason to be made.

Reply to
Robert Baer

either a fault with your multimeter or that cable is broken. (or possibly wired differently)

sounds spurious to me, I don't think VGA signals will pass well thrugh a capacitor.

although a capacitive cable can be used with RF signals to isolate ground loops.

Bye. Jasen

Reply to
Jasen Betts

"Hi Fibo

Could he have meant something like this?:

Fluke PM9080/001 *Optically* *Isolated* RS232 Adapter/Cable: "

- woah, what is this thing used for? I've never seen one of these

"although a capacitive cable can be used with RF signals to isolate ground loops."

- So there is such a thing?

Reply to
Fibo

Double-check the pin numbering scheme. If *all* the pins are showing open, that makes me think that you may be using the mirror image of the proper scheme on one end.

Best regards,

Bob Masta DAQARTA v4.50 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

Reply to
Bob Masta

I would grant that it is probably not a cable with series capacitance, but such a thing is neither impossible nor useless.

If you have a moderately fast signaling scheme, digital or analog, that does not depend on any low frequency component or DC offset, it may be desirable to have A/C coupled interconnect.

Unshielded twisted pair Ethernet is a good example. Normally the DC blocking is done by transformers, but if you are just fooling around on a lab bench for fun it will often more or less work with series caps instead.

Usually I'd think the DC coupling components would be found just inboard of the connector, not in the cable. So I don't really think that is what is happening here, but it's not impossible.

Reply to
cs_posting

prolly for connecting a multimeter with serial output to an earthed device (like an ordinary pc)

I've seen adaptors with TV antenna style plugs, there's no reason why the same circuit couldn't be built into a cable.

Bye. Jasen

Reply to
Jasen Betts

I think it's used to connect a flux capacitor to a refurbigated framagammit. Only used on DeLorean's, so it's very hard to find.

Scott

Reply to
Not Really Me

Used on Delorean's what?

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Reply to
Apostrophe Police

Time travel system.

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