Digital, not Analog

I finally dug into the bowels of the Vitamaster, and found this little number. Our motor theory was wrong. Rather than depending on analog voltage input from a motor in the wheel, the Vitamaster uses what is misleadingly called an "electronic watch." I'm just glad they printed the patent number on that thing, or I may never have figured it out. Behold:

Getting this out without destroying anything proved difficult, but probably not as difficult as putting it all back together

Though patent descriptions read like dry nested story puzzles, it looks like this device is basically two rotating magnets and a reed switch, turned by that uppermost blue arm when the bike's wheel spins. Which (I assume) would mean we would actually be getting digital readings -- an on/off pulse -- and reading the pulse rate. Every time the wheel rotates, the magnets in the rotating trough pull the reed switch together, completing the circuit and thus sending a brief "on" signal once (or twice?) per rotation. Apparently mine is missing one magnet. I'm not sure if/how this affects performance.

Given my earlier (failed) attempt at reading voltage with a multimeter, this now makes more sense: A reed switch, when connected to an ohmmeter, should read either zero or infinity, depending on whether it's closed or open, respectively. I'll have to run another test tomorrow.