Wondering if anyone has done this using a digital multimeter (DMM) with a frequency scale? I tried once, but I suspect the magneto voltage may have been to low to be picked up by the DMM. The frequency I think should be 213 1/3 hz @ 1600 engine rpm. That is calculated by 16 poles/magnets X 1600 rpm divided by 120. Thoughts
Wouldn't there be a pulse for every magnet pass?
Then for 1600 RPM there would be 25,600 pulses per minute or, dividing by 60, 426 2/3 cycles per second. I don't think you need to count the positive and negative parts of a cycle separately.
Where's John Regan when we need him?
I'm betting on Hershey.
Buzz Pound made tachs with a 270° analog meter. Versions were available for dizzy points or magneto frequency. I dearly wish they were still available.
Gail is right, 1600 r.p.m. is 213 1/3 hz. It still can be done and was done by Buzz Pound as pointed out by Garnet. It doesn't work with Ruckstells in low, or low pedal and such. For me it is nearly as easy to hook up a bike speedo, or even easier yet, use a GPS.
The magneto testing function in the ECCT works on this basis.
Multiply frequency by 7.5 to get rpm. Some digital instruments are affected by the Model T ignition system so this needs to be kept in mind when attempting to measure the magneto.