SRM and Cyclingpeaks

the holster said:

my srm speed sensor cable recently tore so i only get power readings. that inturn yields power data only when i am pedaling. i did a race, i was in a break from the gun and my raw data was 350 and my NP1hr was 390, then i got to thinking, are these numbers correct if they never measured zeros?

They are correct as long as you didn't coast long enough for your SRM to actually turn itself off. The SRM doesn't need to measure speed to calculate power, or to "know" that time is passing. Similarly, the calculation of normalized power in CyclingPeaks relies on just power and time.

As a double-check, you could simply look at the graph of power vs. time in CyclingPeaks, and see if certain events (e.g., a spike in power corresponding to a prime sprint) appears to have happened when they should have.

acoggan said:

They are correct as long as you didn't coast long enough for your SRM to actually turn itself off. The SRM doesn't need to measure speed to calculate power, or to "know" that time is passing. Similarly, the calculation of normalized power in CyclingPeaks relies on just power and time.

As a double-check, you could simply look at the graph of power vs. time in CyclingPeaks, and see if certain events (e.g., a spike in power corresponding to a prime sprint) appears to have happened when they should have.

the problem is that without the speed sensor the srm doesn't record time when your not pedaling, so the crit was 1hr10min but the srm file only showed 1hr4min.

the holster said:

the problem is that without the speed sensor the srm doesn't record time when your not pedaling

Mine does, but perhaps you've got your PowerControl configured differently?

Just to confirm: after downloading directly into CyclingPeaks, you find no points in the file where your power and cadence were zero?

acoggan said:

Mine does, but perhaps you've got your PowerControl configured differently?

Just to confirm: after downloading directly into CyclingPeaks, you find no points in the file where your power and cadence were zero?

thats correct. after thinking about it for a while the raw data on the srm will be close to the NP since its not recording zeros and not recording coasting time. and the NP will be over estimating because of that. sound right???

the holster said:

thats correct.

Okay, thanks for the clarification. (You do know you can change it so that it will always record power, heart rate, etc., right?)

the holster said:

after thinking about it for a while the raw data on the srm will be close to the NP since its not recording zeros and not recording coasting time. and the NP will be over estimating because of that. sound right???

The normalized power will clearly be overestimated, but there's no guarantee that the non-zero average power will be close to the true normalized power. In fact, given that it was a criterium, I'd expect non-zero average power and normalized power to be significantly different.