Benching ecms

[Bruce Plecan]

With both ecms "running" having the +5v for the sensors tied together
seems to generate "No Smoke". 

Next question, does this only work with both ecms powered up?.
  Can I have them wired like this and be running only one at a time?.
Seems like there is enough internal resistance to the off ecm not 
to hurt things, but I only did this momentarily.

Would the real answer be using ganged pots?.  I've tried looking in
my digi-key, and a couple other catalogs, but turned up no sources.

When doing pulse generators, is it better to use a 558, and use a
4017 for getting low rpm signals?.   For those veiwing from afar
the reason is that I need to get accurate 200 rpm steps.  The gms
from what I read do interpolation from one step to the next for
timing etc, so I gots to be close, to read changes accurately.

Much more and it seems like a commercial used freguency generator
will be the answer.  So if ya got a working gen please e-mail me.

Thanks again 
Bruce               nacelp at bright.net