Some longer testing (1.5 hours) today and I’ve come to a few conclusions.
- My calibration is off
- It doesn’t matter that my calibration is off, the crank shear gauge on the inside of the driven arm to measure torque can be skewed by adding a twisting moment to your ankle.
- As a result my power balance and power numbers are all wrong! And WAY off from the method of calculating averaged (non-accelerating) power for my Kurt Kinetic Road Trainer.
So I will be adding new strain gauges to V3 on the top and bottom of the crank arm. The arrangement removes bending so it will stabilize and remove this issue. I had said previously that it is the superior arrangement. I didn’t want to have to use two different types of gauges but my hand has been forced. However this raises the question about Stages power meter. What is their arrangement? I suspect it is not a shear arrangement, but rather a double bending arrangement but still on the back side of the crank. It’d lose sensitivity but gains in accuracy.
The ADS1247 is reading out. It’s looking noiser than I want, but this might be a function of my protoboard / power supply / poor wiring / random resistors used as a voltage divider. I still can’t find a potentiometer around my apartment anywhere even though I bought and wired one up specifically for testing months ago. I’ll make a trip to the dollar store tomorrow and hope