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Old 5th February 2004, 04:59 PM   #1
waben is offline waben  Netherlands
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Default DMM, what accuracy should i be looking for

Just about to buy a new DMM to replace my rather crappy current one.
But what kind of accuracy should i be looking for in a DMM?
I grasp the 'as great an accuracy as you can afford' concept...but that would mean buying something seriously expensive and most likely comlete overkill.
So what would do fine for amp building?

Cheers,
WB
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Old 5th February 2004, 06:48 PM   #2
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The most precise component you have in circuit might be 1 or 5% (being the resistors), and I imagine most DMMs are at least that precise, so don't worry about it. It is a poorly designed circuit to need even that much precision anyway!

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Old 22nd March 2004, 08:59 PM   #3
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Quote:
Originally posted by Sch3mat1c
The most precise component you have in circuit might be 1 or 5% (being the resistors), and I imagine most DMMs are at least that precise, so don't worry about it. It is a poorly designed circuit to need even that much precision anyway!

Tim

I disagree with the previous post - the accuracy of the meter you buy should depend wholy on your intended purpose. The tolerance rating of a resistor only tells how far it will deviate from it's rating and not dictate how accurately you want to measure the voltage across or current passing through it.

You should ask yourself the question, "what is the allowable tolerance of any readings I will make?" - if you are working in a medical or military field then a DMM may have to be incredibly accurate (and high tolerance) for it's intended purpose, if you are only making simple circuit measurements on audio equipment then obviously lower accuracy and lower tolerances are acceptable.
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Old 22nd March 2004, 10:31 PM   #4
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Old 22nd March 2004, 10:37 PM   #5
SY is offline SY  United States
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You have to consider what you're using it for. Also, it's important to distinguish between precision and accuracy. Normally, precision is more important.
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Old 22nd March 2004, 10:46 PM   #6
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Although a good precision, good accuray DMM might occsionally
be useful, you may find it better to buy two chepaer DMMs instead,
since that allows you to keep track of two parameters simultaneously.
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Old 22nd March 2004, 10:46 PM   #7
Magura is offline Magura  Denmark
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Just make sure its able to measure true RMS, it comes in handy when working on power supplies.


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Old 22nd March 2004, 10:55 PM   #8
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Originally posted by Magura
Just make sure its able to measure true RMS, it comes in handy when working on power supplies.


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That's overrated I think, at least if you have a scope. Without
a scope, perhaps, but if you cannot see the waveform anyway...
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Old 22nd March 2004, 11:04 PM   #9
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I agree - often true RMS can be calculated with the appropriate correction factor.
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Old 22nd March 2004, 11:36 PM   #10
Magura is offline Magura  Denmark
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Quote:
Originally posted by annex666
I agree - often true RMS can be calculated with the appropriate correction factor.

True, but RMS measuring ability dosnt have to make the DMM more expensive, its just nice to have, hence the advice.


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