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.
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