Dyno tach generator

[Rich M]

>Have a look at frequency to voltage converters. Don't know who
>makes them, but
>it shouldn't take long to find a datasheet. I'm not sure how
>accurate they can
>be, but you should be able to hook one up with a multimeter as a >display,
or
>use the movement in the tach if it is accurate enough.

>A friend of mine put such a circuit into his misbehaving period
>tach. Looks
>completely original from the outside, but reads far more
>accuratly.

LM2907 or LM2917 from National Semiconductors.
Linearity typically 0.3%. You get to trade off output ripple variation
against speed of response/settling time.

I've used them for both retrofit to moving coil tach and for digital
display, both work fine.

Rich