Very very electrical question., Tachometer waveform Options

[sgomes]

Ok, I don't expect to get an answer to this question but here goes nothing:

I've got this fancy tacometer drive thingy that is supposed (IMG:style_emoticons/default/unsure.gif)

Assumptions about the tach:

It expects at least +5V pulses more is ok.
It assumes a four cylinder engine.

My assumption on how tachs work:

You get one pulse for every spark. So.....

assume 6000rpm for the sake of argument
6000rpm= 100 revs per second * 60 seconds
4 sparks per revolution.
4 * 100 = 400 pulses per second.

I've got something close to 200 pulses per second comming out of my sender at about +10V.
The tach isn't moving.

[lapuwali]

There aren't four sparks per crank revolution. There are four sparks per distributor revolution, which runs at half the crank speed. So, 200 sparks per second is correct for 6000rpm.

I'd expect 13-14v pulses from the low-tension wire on the coil, since that's what the voltage regulator really regulates the system voltage to, not 12v, and certainly not 10v. Dunno why you'd assume the tach would work with 5v.