AC _DC amp meter

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AC _DC amp meter

Peakfoto Digital Photo Still n Video
 

What do you mean by "fairly accurate down to thousands"?  

Milivolts for measuring individual LFP cells for balancing n charging etc..


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Re: AC _DC amp meter

EVDL Administrator
On 24 Sep 2013 at 20:48, Peakfoto Digital Photo Still n Video wrote:

> Milivolts for measuring individual LFP cells for balancing n charging etc..

Just be careful.  Cheap multimeters are notoriously inaccurate.  Some vary
their readings with temperature.

I'm not an expert, but my impression has been that clamp ammeters are mostly
for by-guess-and-by-gosh measurement.  I don't think they're ever all that
accurate.  Certainly the ones I can afford aren't. ;-)

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: AC _DC amp meter

Jeffrey Jenkins
EVDL Administrator wrote
....
Just be careful.  Cheap multimeters are notoriously inaccurate.  Some vary
their readings with temperature.

I'm not an expert, but my impression has been that clamp ammeters are mostly
for by-guess-and-by-gosh measurement.  I don't think they're ever all that
accurate.  Certainly the ones I can afford aren't. ;-)

David Roden - Akron, Ohio, USA
EVDL Administrator
....
Yes, this. I have 3 different model Fluke clamp meters and 2 clamp probes that all agree within 10A at 1000A (ie - 1%). We also have 4 other different brand clamp meters and not a single one agrees with the others, much less the Flukes, and are off anywhere from 30A, at best, to 100A typical (and invariably they read low, which is especially bad in my opinion).

And for mV accuracy don't even think about a clamp meter... Voltage readings on them are more or less an afterthought, even for the Flukes.

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Re: AC _DC amp meter

David Nelson-5
This link was posted over on Insight Central and I wondered if it
might help for those wanting to check the accuracy of their DMM
voltage readings: http://geoffg.net/Voltage_Reference.html. It looks
quite simple and am thinking of making it just to see how my meters
are doing.

Jeff, are you implying that if I want reasonably good voltage
measurements I'd be better off with a non-clamp meter? I have an
Extech EX830 so don't really know how accurate it is.


On Wed, Sep 25, 2013 at 7:34 AM, Jeffrey Jenkins
<[hidden email]> wrote:

> EVDL Administrator wrote
>> ....
>> Just be careful.  Cheap multimeters are notoriously inaccurate.  Some vary
>> their readings with temperature.
>>
>> I'm not an expert, but my impression has been that clamp ammeters are
>> mostly
>> for by-guess-and-by-gosh measurement.  I don't think they're ever all that
>> accurate.  Certainly the ones I can afford aren't. ;-)
>>
>> David Roden - Akron, Ohio, USA
>> EVDL Administrator
>> ....
>
> Yes, this. I have 3 different model Fluke clamp meters and 2 clamp probes
> that all agree within 10A at 1000A (ie - 1%). We also have 4 other different
> brand clamp meters and not a single one agrees with the others, much less
> the Flukes, and are off anywhere from 30A, at best, to 100A typical (and
> invariably they read low, which is especially bad in my opinion).
>
> And for mV accuracy don't even think about a clamp meter... Voltage readings
> on them are more or less an afterthought, even for the Flukes.
>
>
>
>
>
> --
> View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/AC-DC-amp-meter-tp4665328p4665338.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
> _______________________________________________
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>



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Re: AC _DC amp meter

Jeffrey Jenkins
David Nelson-5 wrote
This link was posted over on Insight Central and I wondered if it
might help for those wanting to check the accuracy of their DMM
voltage readings: http://geoffg.net/Voltage_Reference.html. It looks
quite simple and am thinking of making it just to see how my meters
are doing.
This is more or less how I check my meters for accuracy, and I suspect most practicing EEs do the same (certainly no one I know uses a Weston cell!). I like to test at 1.25V and 2.5V to see if there are any linearity errors. If the meter reads off by more than 1% then I send it in for calibration, otherwise I keep on using it. The Fluke 179 that I bought 3 years ago (with NIST calibration) has not deviated more than 0.5% (using 0.1% voltage references) while the el cheapos I got from Harbor Freight (mainly for the bead thermocouple) wander as much as 5%, especially with a change in temperature. I also test the DC mA range by inserting a precision (0.1%) 125 ohm resistor in series with the reference voltage. Same stability with the Fluke; same wackiness with the el cheapos.

David Nelson-5 wrote
Jeff, are you implying that if I want reasonably good voltage
measurements I'd be better off with a non-clamp meter? I have an
Extech EX830 so don't really know how accurate it is.

> On Wed, Sep 25, 2013 at 7:34 AM, Jeffrey Jenkins
> And for mV accuracy don't even think about a clamp meter... Voltage readings
> on them are more or less an afterthought, even for the Flukes.
Implying? More like bluntly stating! ;)

More specifically, my Fluke clamp meters only resolve down to 0.1V, while my 179 DMM resolves down to 0.001V (ie - 1mV) on the 6V scale.
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Re: AC _DC amp meter

Rush Dougherty
Very nice...

Will build one to see how accurate the 4.95 chinese meters are.

Rush
www.TucsonEV.com


>
> David Nelson-5 wrote
> > This link was posted over on Insight Central and I wondered if it
> > might help for those wanting to check the accuracy of their DMM
> > voltage readings: http://geoffg.net/Voltage_Reference.html. It looks
> > quite simple and am thinking of making it just to see how my meters
> > are doing.





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