Powering 8-ohm speaker through ~130 feet of RG6 coaxial? - Page 2 - AVS Forum
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post #31 of 44 Old 08-20-2013, 04:19 PM
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As promised:


Here's the DMM with the leads open. It reads "OL" which is pretty standard for a DMM on infinity.


And here with the leads shorted. Ahh wait it's not zero ohms but rather 00.3. Hmm the wire leads and connections have some resistance so I guess a "dead short" is not so dead is it? Further evidence that shorting the end of a 100 foot coax cable is not going to read zero ohms even on a cheap DMM such as this one. Now a competent technician or engineer would carefully verify that error in the meter leads and cancel it out of the final reading. But we are now getting way ahead of you Gregzoll.
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post #32 of 44 Old 08-20-2013, 04:37 PM
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Quote:
Originally Posted by fcwilt View Post

And while I am a fan of MP I don't remember what is taking place in the referenced photo. What is the name of that sketch?

I would like to go watch it again.

eek.gif

"Argument Clinic"

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post #33 of 44 Old 08-20-2013, 05:02 PM
 
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And for many decades people have been shorting the test leads to get a zero voltage reading and then pressing the little calibration button. That would make no sense if that resulted in infinite resistance.

Infinite resistance means there is no flow. Zero resistance means there is full uninhibited current. It's a short circuit. It's also common usage in English language as in, "She offerred no resistance to my arguments." Or for fun, "She gave me infinite resistance to my advances" - which is definitely not a short circuit condition.

I = V/R (Ohm's Law) if I have an infinite resistance than the current will be very very small (R is very big swamping the V). If I have 0 resistance then I is infinite as in a short circuit.

Wow. Can we argue the validity of Ohm's Law next? rolleyes.gif

For fun, ask him about HDMI cables and differences.

Here's a reference. if it is really needed:
http://en.wikipedia.org/wiki/Ohm's_law
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post #34 of 44 Old 08-20-2013, 05:44 PM
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Originally Posted by Glimmie View Post


INFINITE OHMS. Note the open meter leads. The needle is at 1Kohms which is actually the infinity symbol but it's too small to see here.


ZERO OHMS: Note the shorted test leads. The needle is on 0.

You may have found the answer.

If you haven't taken the time to understand all the different scales on a analog meter you might think because the needle is to the left (which would be zero for volts, etc) that it is also zero for resistance.

And by the same "reasoning" infinity ends up on the right.

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post #35 of 44 Old 08-20-2013, 05:52 PM
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Quote:
Originally Posted by jautor View Post

eek.gif

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http://www.youtube.com/watch?v=kQFKtI6gn9Y

Thank you very much.

Regards, Frederick C. Wilt
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post #36 of 44 Old 08-20-2013, 05:55 PM
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Quote:
Originally Posted by fcwilt View Post

You may have found the answer.

If you haven't taken the time to understand all the different scales on a analog meter you might think because the needle is to the left (which would be zero for volts, etc) that it is also zero for resistance.

And by the same "reasoning" infinity ends up on the right.

Agreed. But if you don't understand the scales, how are you going to use the meter? It's interesting how Gregzoll tells others to get an education in basic electricity (and in numerous posts, not just here) and how we don't know anything yet he clearly in his own words demonstrates he is the one who needs this basic education. He clearly has no idea of what electrical resistance actually is or means.

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post #37 of 44 Old 08-20-2013, 06:06 PM
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How many times have you seen the "phrase" RTFM?

We know that many (most?) folks don't

So it would not surprise me at all that folks would buy equipment but never really learn to use it correctly BUT believe they have.

But for this person the obvious lack of understanding makes a curious contrast with the insistent declarations of education and knowledge.

I wonder what this person does for a living. It might be entertaining to be one of his co-workers.

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post #38 of 44 Old 08-20-2013, 07:37 PM
 
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...or scary. I'd hate to have my life depend upon those decisions.
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post #39 of 44 Old 08-20-2013, 07:53 PM
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Where did he go? The posts seemed to have stopped.

Do you suppose he went to RTFM? smile.gif
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post #40 of 44 Old 08-20-2013, 10:33 PM
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Quote:
Originally Posted by fcwilt View Post

Where did he go? The posts seemed to have stopped.

Do you suppose he went to RTFM? smile.gif

It looks like some posts were deleted? Usually the moderator announces any edits? Posts 32 & 33 are not the same posts as before.

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post #41 of 44 Old 08-21-2013, 05:28 AM
 
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I wonder how the OP is doing (we kind of lost track of the original issue)? Does the wire impedance change with frequency (in the audio range, of course)?
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post #42 of 44 Old 08-21-2013, 07:38 AM
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Quote:
Originally Posted by alk3997 View Post

I wonder how the OP is doing (we kind of lost track of the original issue)? Does the wire impedance change with frequency (in the audio range, of course)?

Yes it does. The question would be by how much - would it be enough to be audible - and that would depend on the quality of the source and the speaker.

Easy enough to measure though with the right equipment.

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post #43 of 44 Old 08-24-2013, 12:27 PM
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Quote:
Originally Posted by Glimmie View Post

As promised:
And here with the leads shorted. Ahh wait it's not zero ohms but rather 00.3. Hmm the wire leads and connections have some resistance so I guess a "dead short" is not so dead is it? Further evidence that shorting the end of a 100 foot coax cable is not going to read zero ohms even on a cheap DMM such as this one. Now a competent technician or engineer would carefully verify that error in the meter leads and cancel it out of the final reading. But we are now getting way ahead of you Gregzoll.
That's what the "Zero" knob (Ohms on the Triplett) is for. Higher end DMMs may have that same "Zero" function as well, but I don't know.

CIAO!

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post #44 of 44 Old 08-25-2013, 01:08 PM
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Quote:
Originally Posted by egnlsn View Post

That's what the "Zero" knob (Ohms on the Triplett) is for. Higher end DMMs may have that same "Zero" function as well, but I don't know.

Correct. But DMMs are far more sensitive. You would be hard pressed to see 0.3 ohms on an analog meter at a full scale of 1K ohms. Sometimes re-inserting the leads will clean off any oxidation and this helps zero it out.

And as I stated above although dismissed by another "expert" low batteries will compromise low ohm (<10) readings accuracy. I have experienced this on several brands of DMMs over the years.

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