Tachometer for phone

[Windmill John]

Possibly been covered, but just purchased Soundtach.
I tried it free for six days then trial expired. Needed it and at £5, thought it was a good investment.
In the past, I normally use my Draper VMM which includes an inductive tachometer pickup. But, on My CM400, I can only think that the double insulation on the HT lead was restricting the signal; unless my tick over was actually 1rpm
Anyway, the app works very well and works for two strokes as well as four strokes, singles as well as multis.
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[stl360+450]

Pretty cool. I was thinking about this recently and it's no surprise that there are polished apps doing the acoustic tachometry.

Are there any conditions that cause it to give sketchy readings? Nearby diesel engines, other bikes, etc.?

 

[Cycleranger]

A tach for your phone? To measure how fast your phone is spinning?