I have an old unit that does Tach, dwell, and something else... Can't remember right now, you have a pos. and neg lead that hooks to the battery and then a clip that goes on number one spark plug wire.
I knew an electronics technician in a lab back in college and he calibrated the tach for me, works really well. I checked it on several cars and they all match. He could never calibrate the dwell, he said it could be done but we never spent the time setting it up. Hope this helps.
The easiest way to test it would be to borrow a know good one and compare the readings you get with them. You would need some sort of calibrated signal generator to do much more that that. Some high end digital meters have a function called duty cycle which in effect is a dwell meter measuring in percent rather than degrees that could be used for a comparison
Well, I did check for an internal battery, and there is none. I could try testing a known good meter against this one, but the problem with my meter is that it's not reading anything at all -- just zero. At the moment, I'm not concerned with accuracy; I'm concerned with it functioning.
I appreciate the help so far, and I'm open to some more thoughts....
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