Fluke 337 Meters

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tkb

tkb

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MA
We are using the Fluke 337 clamp amp meters and when we are measuring 20 amp circuits in a data center PDU with no load we get a reading of 0.1 to 0.4 on the display.

I know it has something to do with the RMS something.

Does Fluke make a clamp meter for measuring AC circuits below 100 amps that will be accurate down to 0?
 
All of the 337's we have will never read zero when set to AC amps.
The zeroing button only works for DC amps.
 
101029-2043 EDT

tkb:

Look at the specifications at:
http://support.fluke.com/find-sales/Download/Asset/1629613_C_w.pdf

AC current range is 999.9 . Probably meaning it is quantized to 0.1 A. That means it increments by 0.1 A.

Then look at accuracy. Between 10 and 100 Hz it is specified at +/-%2 plus 5 counts. This probably means % of reading +/- 5 counts. A count means 0.1 A in this case. The % accuracy probably means of reading, although not defined, and at 1000 A that would be +/- 20 A, and the count part is not significant. At a 20 A level the error is the % error of reading (+/-0.4 A) +/- 0.5 A by my interpretation.

If I compare my 87 with my 27 I see what appears to low level noise on the 87 that I do not see on the 27 on the MV AC range. I attribute this to the RMS converter.

The Fluke 337 is not a high accuracy unit on low current levels. For this meter 20 A is a low level current, it is 2% of full scale.

The accuracy specification does not mean the meter is as bad as the specification. Also see how ambient temperature affects accuracy.

Relative to reading zero your meter is well inside of the accuracy specifications.

.
 
If anyone is interested, Fluke doesn't list the input impedance for their clamp meters anywhere. I emailed them the other day to ask about that. They responded that it's 1M.

I don't have a Fluke clamp meter but I do have a AEMC F07 which also has a listed 1M input impedance. At 1M that's not low enough to eliminate "ghost" voltage.
 
As gar said, you will need to pick out something with a lower range and better accuracy. As you noted, 1000A and 2% is pretty rough for measurements around zero.

I've got an Extech 200A mini AC/DC. It is 1% and 2d. It's not a lab instrument, but works pretty good at 100A levels. As I recall it was $225. There are likely plenty of other brands out there as good or better - maybe even cheaper.

As other have alluded, just because a meter has a .1A resolution doesn't mean the accuracy is anywhere close to .1A

Such be one of the banes of digital instrumentation (and calculators)

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ice
 
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