mtbr wrote:
RChung wrote:
Tom A. wrote:
C'mon people...NO powermeter should be put into service without at least a static torque check...and if the PM doesn't allow for that, you might want to reconsider the use of it.
People buy PMs based on features, and that's a mistake. Being able to check the accuracy of your PM is like having the 9 key on a calculator. It's not a feature, it's a key.
Why is there an assumption that a static torque check will verify every calibration?
Has anyone ever put a Quarq or SRM on a dyno to see if their static calibration is in fact correct?
I have dealt with rotary torque cells that cannot be calibrated by hanging weights alone.
The AIS has published a number of studies comparing the outputs of SRMs, PTs, etc. with dynamic calibrations, which I'm sure you can find in a web search.
Also, take a look at a typical crank torque plot, and you'll easily see that the vast majority of the torque is applied through a fairly narrow range, so checking the torque output in that same area is going to result in a pretty good idea of how well it will be able to measure the power output of a human cyclist. Once you have that, measuring average crank rotational velocity is fairly trivial, and those are the 2 inputs to calculate power.
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