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propagation of back EMF

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Simon:
well as I said there are 6 8 amp fans running all the time, they have built in speed control resistors and indeed things are worse when they run at speed 3 (no limiting resistor) so ringing I expect is natural, what i never expected was the fact that I would get bursts of ringing, basically what you see happens maybe 20+ times but each burst is quite spaced out (like 10 times the length of the main burst) and only the first burst is so large but I guess that is because it is the initial energy that jumped the relay contact gaps. As this relates to a 2 piece military vehicle things certainly will be more hectic than with my little set-up and I've already warned them that these phenomenons are quite a physical thing and can only be faithfully replicated by using the actual installation which is likely to never happen

Rhythmtech:
Usually when I've gotten to this stage I start thinking Heisenberg's Observation effect - Which abstracted on to what you are doing says that you effect your measurement by simply making a measurement.  Is it possible that some of the voltages you are seeing are being incurred by probe impedance or other measurement variables?

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