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Remy Blank wrote: |
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>Iain Buchanan wrote: |
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> |
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> |
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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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>> |
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>> |
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> |
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>Or only the neutral. It doesn't matter, actually. |
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> |
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> |
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> |
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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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>> |
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>> |
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> |
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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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> |
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>-- Remy |
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> |
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> |
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>Remove underscore and suffix in reply address for a timely response. |
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> |
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> |
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> |
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Well you almost got it right. The clamp is just a basic transformer |
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being the secondary winding. Since AC current flow changes both in |
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amplitude and direction, induces a current flow in the secondary |
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winding, "the clamp". The current is then rectified and the measurement |
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then is displayed on a meter. I've used high voltage transformers from |
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old monitors to monitor and trigger alarms signaling excessive current |
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change. Basically just a home made clamp. |
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Cheers. |
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-- |
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Ted Ozolins(VE7TVO) |
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Westbank, B. C |
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|
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-- |
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