The sensors are on the axle itself and with a tyre diameter of 33.03 inches and I've calculated to be a maximum of 180km/h the be around 1100rpm. So 1100 x 48 ÷ 60 = 880Hz.

33", eg 275/70R18, 381 revs/km so 1143rpm @180km/h = 914Hz, but whats the bottom end? Its 5Hz per km/h

 

Yes,though some experimentation with capacitor values might be needed...

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How would I go about amplifying the ac signal up to 5-6 volts peak to peak.