Freaky Amazing DMM?!



I have a few $3 DMM's from Harbor freight, but they're 2Mohm impedance in the 200mV setting.
PL
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on 16/01/2009, Paul supposed :

The evil thing about Voltmeters with very high impedance is they will read induced voltages that analog meters wouldn't. It makes a voltmeter useless for checking for live circuits in a crowded panel.
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Why? If the source has a low resistance/impedance then you're ok as soon as you have good probe contact. If not, then you could always twist the probe leads together a bit to try to make a balanced line to cancel induced noise. Crude, but it would help if the signal to be read was DC or audio AC.
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wrote:

A craftsman never blames tools for his failures. Hackers, on the other hand...
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krw explained on 19/01/2009 :

If you work with electricity you had better know the limitations of your tools or you will find them...the hard way.
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snipped-for-privacy@gmail.com says...>

m...
That is certainly true (though perhaps your heirs are the ones who will find you), but doesn't modify my statement. In this case, the tool *can* be used as long as the one using it knows what he's doing.
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krw used his keyboard to write :

Ok....everything seems to pass right over your head.... I pointed out a limitation of a DMM and you seem to be inferring that I am somehow a hack who blames his tools... BTW> I am not a "craftsman" I am an electrcian.. You don't do what I do for as many years as I have without knowing what the fuck you are doing.
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snipped-for-privacy@gmail.com says...>

com...
No, your incompetence didn't pass by anyone.

It is not a limitation of the tool, only the user. Lower the impedance if it's too high.

I'll take your word that you don't do "craftsman like" work. You clearly don't know how.

*I* know what I'm doing. You've clearly demonstrated that you don't.
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this immortal opus:

What's wrong with using a hi Z voltmeter in a live panel? I do it more often than I really care for, and never have a problem.
- YD.
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It's not the right tool for the job. A meter which gives you a false reading with bad (or no) contact is a BAD idea in dangerous high voltage/high energy circuits. That is why proper meters with low impedance (Kohms) modes exist for the job, e.g. Fluke 113, 110 series, 289 etc.

Oh dear...
Dave.
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penned this immortal opus:

>>>>>>>
The circuits are loaded, so any bad contacts will certainly affect the reading. Which is the way I like it. Any funny readings, move up to the next point in the line and check there.
I do know better than to measure an unloaded line without sticking some suitable load across it.
Anyways, AIUI, this started with a meter with Hi-Z in the mV range, most DVMs use a 10M or 1M divider at higher ranges.
- YD.
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There isn't anything wrong with it. Analog meters are dead. High impedance digital meters are only a problem if there is a loose nut inside the panel, holding the leads.
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>>>>>>>>
Then I suppose Fluke and others make all those purpose designed Low-Z electrical meters for loose nuts then?
Dave.
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On Tue, 20 Jan 2009 19:06:15 -0800 (PST), "David L. Jones"

>>>>>>>>
...and electricians who know nothing about electricity, perhaps.
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>>>>>>>>
But at least smart enough to chose the right tool for the job.
Dave.
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In article <9caaa5aa-54e2-4f21-a324-1f2ca8bdd389

>>>>>>>>
For an electrician who know nothing about electricity (99.44% of them, apparently), or if that's all one is ever going to do with the meter, perhaps. For anyone who knows anything about electricity or wants a tool that has more than one use, the high impedance meter is a better choice.
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Totally useless in areas of high RF.
As the man says, the proper tool for the job
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says...>

Wrong.
Know what you're doing is a better solution. Loose nuts are dangerous.
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That statement simply exposes another large hole in your knowledge and experience.
I spent 20 years on a high power HF transmitting station - believe me - I *know*

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I would agree. Take two meters. One is 1Kohms. The other is 1Gohms. If the load is low impedance, say 100 ohms, then there's an appreciable error with the low impedance meter-- simple ohms law. While the error associate with the high impedance meter is unmeasurable.
People are probably confusing the fact that a high impedance meter while unconnected to anything will pick up signals, for obvious reasons.
Paul
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