Hi,

Your answer is here :
Excel comes up with the correct answer. for 1 ADC count the result comes out at 6.1266 knots
you have to use a signal amplifier to get more ADC counts for the same outputted voltage ...

A logarithmic amplifier could be a nice idea to get a linear ADC input voltage Vs Speed.

I remember some really good work had been done here for Vu-meters ... ( a greek project ... )

CA3089 or NE 604 could be some interesting keywords to try ...

have fun

Alain