measuring hall output

[Orin Eman]

> Hence, my question about if I can just calculate the position, by
> telling the ecu vendor that the falling edge is 20 degrees ahead of
> 62 btdc, and the rising edge is 20 degrees after 62 btdc.

Yes, if the distributor is properly set which it won't be.
To be honest, that measurement wasn't particularly accurate, so
just use one edge of the signal.  Let me make this perfectly clear...
you will have to set the distributor position with a timing light if
you are using it to drive the ignition.  The ECU will set a particular
timing at idle, you put a mark on the flywheel at that point and
you rotate the distributor until that mark is at the bellhousing
reference as seen with the timing light when idling.  There is no need for
anything fancy to place the mark - each flywheel tooth is 2.7 degrees.
Count teeth from the zero and interpolate as necessary.

There is nothing magic about the positioning of the hall sensor window
if you aren't using the timing pin.  It's just that if you use the
existing reference marks on the distributor, that's where the window
will be.

> I've been afraid to proceed with measuring things for fear of
> damaging something.  I'm a bit gun-shy about the hall sensor,
> because remember a friend having to replace one after damaging it
> by checking for spark improperly, iirc. (not grounding the plug body
> can fry it?)

Not grounding the coil wire and turning the engine over with ignition
on can fry just about anything.  Just don't do it.

Orin.