Fluke makes very good meters and if anyone can make a clamp on DC meter work they can. I love my Fluke meters but do not have a clamp on DC one. However it is a difficult technical and electrical situation to measure the steady magnetic field around a wire with DC current in it vs. the varying AC current. When you look at the range of clamp on meters you will find very few are available that attempt to measure DC current, which tells you something about the issue.
The one I have, which is a Craftsman from Sears, is hard to zero, and hard to get a repeatable number from test to test. I simply don't have any confidence in it at all. I have an inexpensive AC clamp on meter which is accurate, repeatable measurements and all things are good.
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