I can also confirm the pulses, i found an old 1K 25 watt wire wound pot, and can detect the pulse using my hall, but it's only there for a second or so the pot heats up pretty fast, next task in to film it  As usual i screwed up something showed up which looked exactly like the pulse, it disappeared after a couple of seconds when the pot warmed up, the pulse was in phase with the ac waveform across the pot, but then i realized i could pick the pulse up anywhere round my bench, so powered off the variac it goes away, switched back on and it's amplitude varies with the variac setting but the hall sensor is no where near, so i disconnect the pot, blow me it's still there again varies with variac setting now this means the variac has no load, what the hell, I'm getting some sort of earth loop between my hall psu and the variac which are tied together via the scope earths, even though my psu is not earthed and uses a transformer? The strange thing about it is that it goes after a couple of seconds when the variac has a load, it's definitely some sort of earth loop though because i see a little spark when i connect my scope earth to one side of the variac. Looks like i will need to sit this out until the wire arrives. This is probably a total waste of time but Just in case this means something i have filmed what i am seeing, the hall is not placed near anything of interest while scoping except when i place the north or south pole of a horseshoe magnet near it. [youtube]http://www.youtube.com/watch?v=llIqI8krieY&feature=youtu.be[/youtube] Having thought about the hall, when the north is used it drives the hall to the positive rail and when south is used then it drives to the 0V rail, so that explains that i think, so it's noise on my rail or a ground current as i said earlier, i wonder why it disappears after a second when the variac has a load.
« Last Edit: 2012-08-12, 22:15:50 by Peterae »
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Topic: Hot Coil Electromagnet (Read 80219 times)
