Hi Itsu,
I just did some tests with a setup similar to yours. I replaced the wire with an iron bar covered in stainless steel. When I place the magnet at one end, I don't see much change. If I leave it there for 10 to 20 seconds and then remove it, I see an increase of between 20 and 40 µV, followed by a slow decrease. But this effect, which I've seen several times, doesn't seem to be systematic. As in your configuration, there is indeed at times a clear signal of a current that appears to be abnormal. But there are several possible reasons and it is difficult to identify them (for example, contacts between different metals to establish the circuit, e.g. copper/iron, we know that these junctions create DDPs). It needs to be explored further. I am lucky to have an old but reliable HP 3468A, which measures µV directly. In the photos, the white areas just hide the mess :-). We can see that we only had 2µV with the magnet, but 21µV just after I removed it and before the voltage slowly dropped.
Hi F6, i was hoping that someone with a good uV meter would join in, so thanks for that. I, too, see very little response (only +-1uV) on my short iron wire (30cm) compared to the earlier used 1.6m wire, even with longer connection leads to create a comparable "loop" length. I also noticed that touching the wire and/or connectors/magnets with my fingers will cause a much bigger voltage swing (10 to 15uV) which stays on for several minutes then simply using the magnets only. So therefor i carefully try to avoid touching anything with my fingers when working on the setup. But the effect you mentioned of not seeing much change when connecting the magnet and only after removing the magnet to see a 20 to 40uV change, i have not noticed here. (by the way, it can initially take up to 5 minutes for a reasonable change to be seen here). Could it be that the makeup of your rod (an iron bar covered in stainless steel) has anything to do with this? Anyway, perhaps you find the time to look for a 1.6m @ 1.5mm piece of garden iron wire to repeat your test. Itsu
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