Re: Hooking Up Dwell Meter

Posted by KEB on August 16, 2006 at 10:27:38 from (192.31.106.35):

In Reply to: Hooking Up Dwell Meter posted by magman on August 16, 2006 at 06:30:00:

Dwell/tach meters will not work on a magneto. They measure dwell by measuring the percentage of time there is a DC voltage at the points (points open) and converting that to an equivalent number of degrees based on the number of cylinders. A magneto does not have constant DC on the points, only a pulse just before the points open, so there's nothing to measure the percentage of.

Remember dwell is nothing more than another way of measuring point gap. Setting the correct gap will give you the correct dwell unless there is serious wear in the distributor.

The tach function probably also doesn't work correctly, as its expecting to see pulsing DC as the points open & close, and actually gets a short pulse just before the points open on a mag. An inductive tach that clamps onto a spark plug wire will work just fine regardless of the source of the spark (magneto, distributor, electronics, etc.)

Keith

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