Hi there, I'm looking for some direction in creating an onboard tach for my rc helicopter that reads its input from a hall sensor, mounted on a model engine, that measures engine RPM up to say 25,000 rpm to be safe. Then I divide the read engine rpm by the gear ratio of the helicopter (8.50), to give rotor headspeed in rpm, and output to a 4 digit 7-segment display. Any help would be very much appreciated.

Regards,
ZipPhReaK