An analog tach is easy to make as you feed the CAS through a 4050 CMOS
gate and feed the nice rectangular wave pulse through a diode into a
capacitor. There needs to be a resistor across the cap to bleed the
charge other wise you will just get constant DC. A bit of experimenting
with the value of the cap and resistor and you are home free.


Paul Lamar


... speaking of capacitors and filtering...
I assume you have capacitors all over the place for noise suppression on
your engine electronics.  All the sample-application circuits supplied
with the analog sensors I purchased illustrate adding capacitors to both
the input and output sides of the sensors.

With the high-powered ignition systems you use there is potential for
all sorts of induced signals.  Do you use capacitors near the sensors?
Use shielded wires?  What kind of spark-plug wires do you use?  Have you
ever had to use a choke on any instrumentation circuitry?

R Bergland