Nyon power measurement accuracy

Johnny

Well-Known Member
I am using Nyon to regulate my workout intensity when I ride for pleasure. Instantaneous power measurements read on Nyon tend to be accurate (matches with the readings on fellow riders wattmeters when we ride together) however average power measurement seems to be quite off.

Today I went for a 15 mile ride. I did the ride with NO assistance hence I was using Nyon just just to check my power. Kept my power 250+ watts a good portion of the time and tried to keep it over 200W at all times. From time to time I had to stop for pedestrians and had to coast a little when my speed is simply too high on descents. The average power decreases at a very high rate even if you stop/cruise 15 seconds in 15 minutes(like a 10W drop on average which doesn't make sense at all since for such a drop I need to be averaging 600w up to that moment).

After the ride I checked Strava estimate and it was a little over 210W but Nyon's average was only around 140W. I made the same loop before with a roadie friend with a power meter and power meter average and Strava estimate was within %5-8 error(Strava's estimate vary when there is wind or the terrain is changing rapidly etc). But even if I assume the worst and adjust the estimate accordingly it still should be way above 140W.

If you keep same cadence and somewhat similar power output for a long time without any interruptions then it seems to have accurate output.

It may be a problem of the Gen 2 CX motor's torque sensor not sampling at a high rate. When I stop pedaling even for a moment and start again the power meter output stays at zero for a second or so before registering the power again (so in the graph I have lots of 0W to 200+W transitions) and this may be the reason behind the measurement accuracy problem.