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Iain Buchanan wrote: |
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> um, I just came across a problem - it won't work with an AC power cord, |
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> because you have active and neutral both going through the clamp in |
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> opposite directions, hence they'll cancel each other out. You need only |
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> the active going through the clamp... |
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Or only the neutral. It doesn't matter, actually. |
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> But "how it works" (with AC) is something like this: AC produces a |
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> field around the wire as it "flows". This field in turn will induce a |
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> current in a wire placed close to it. Loop a wire (transducer) around |
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> another wire (AC current flow), and you can inference the change in |
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> current in the original wire by measuring the current flow in the loop. |
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> |
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> It doesn't work with DC, as DC doesn't create a field (at least, not |
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> when it's steady. When switching on and off a DC device, you'll still |
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> get a change in current) |
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> |
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> IANAE(lectrician), so this might be complete bunkum, but that's how I |
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> remember it anyway. |
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You almost got it. Actually, it's not necessary that the current be AC: |
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even a DC current produces a magnetic field around the conductor (albeit |
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a DC field). The clamp is a ferromagnetic ring that "concentrates" the |
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magnetic field, and it is interrupted at one location by a hall-effect |
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sensor that measures the magnetic field. The current can be calculated |
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from the magnetic field intensity and the diameter of the clamp ring. |
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-- Remy |
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Remove underscore and suffix in reply address for a timely response. |
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-- |
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