Testing tach

[Destroyer]

Originally Posted by Joker2

I have heard that for my motor it should be set to 6 as I have a 12 pole alternator, correct ?

Correct

Here's why: A signal that drives the tachometer is often taken from the permanent magnet alternator. Typically the signal is taken from the stator coil output as it is applied to the rectifier. The attachment of the battery and the rectifier to the circuit affects the ouput of the stator coil somewhat. The positive voltage peak is limited to about a volt above the positive battery voltage, and the negative voltage peak is limited to about volt below the negative battery voltage (or ground). This signal is a half-wave rectification, so it has half the frequency of the full-wave output. If the alternator has twelve magnets, the tachometer output will have six pulses per rotation. Hope this helps.

[Joker2]

Thanks !