Based on this, would it be safe to say the signal is being generated from a position sensor in the flywheel? Not a rotorary encoder? Is it possble to tell the difference based on signal characteristics?
Whether it's specifically a position sensor, I don't know, but it's definitely not a digital encoder given that the signal is not a pulse train.
Also, I would like to get a direct measurement of force production... I am thinking of adding a tension/compression strain guage to the connector rod at the bottom of the bike between the lever arms and pedals... Any suggestions for what to use for this? Are "bolt on" strain guages any good?
In what direction do you want to capture force? Always in the downward direction, or always orthogonal to the lever? If you put a bending sensor (strain gage) on the connector rod, then which force orientation you'd capture would depend on whether the connector rod is rigidly connected to the pedal or to the lever.
Either way, I've never used a bolt-on strain gage, so no comment there. I almost wonder if there were a low-profile sensor with a large surface area that would sit between the pedal and the biker's shoe so you could get the force even more directly, but this would only be helpful if capturing force in the downward direction. If you wanted to capture force orthogonal to the lever, I'd be more inclined to use a torque sensor on the central shaft and then back-calculate force using the length of the lever. This seems simpler than trying to get a gage properly mounted in the right geometry on the tiny connector rod, though it would be even less direct a measurement. I'm definitely not an expert on mounting sensors, so take these comments with a pinch of salt.
