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T-Series & Prewar Forum

measuring dwell angle with positive ground

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sonofmagni Avatar
sonofmagni Karl Thorkildsen
Mason, NH, USA   USA
This might important for people with positive ground vehicles. Unless my logic is wrong, if you use a conventional analog dwell meter, your dwell measurement will not read correctly. Because the meter is measuring the time that the signal is the same level as the minus side of the battery, your actual dwell is the difference between 90 and what the meter reads. Of course this is assuming your meter doesn't have a setting for positive ground.

Can anyone confirm or dispute this?

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sonofmagni Avatar
sonofmagni Karl Thorkildsen
Mason, NH, USA   USA
I confirmed this today. With my analog meter designed for neg ground, increasing the gap increasing the reading. Hence the reading is inverted and need to subtract what the meter reads from 90.
Another way to think about it, because the points connect to +12 (ground) the meter thinks the points are open when they're closed.

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