Power meters · Public discussion

Initial PowerTap settings

Started by MikeMuk · · Last activity · 28 posts · 3,068 views

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Power meters
Published
26 August 2006
Last activity
24 November 2006
Original author
MikeMuk
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28
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  1. AFAIK, it should match - always does with me. Is your PT CPU sampling rate set at 1 sec (actually 1.26 secs) or at a longer sample rate like 2 or 5? I'm not sure if that would make a difference - but what I do know is that, say you have 5 sec sampling - it only records the data point every 5 secs (discarding the others) and not an average of last 5 secs. So maybe (and I'm only guessing) the peak occured during the non recorded data points but it still updated the Max Watts reading in the CPU.

    Bike N Ski said:

    On my last ride I did a 30 sec sprint where max. watts read 1396 on the display. However, in cycling peaks software my max. watts recorded for the entire ride was only 941. Is it a case that the higher reading wasn't stored or sampled as a datum point in the file but only maintained as my peak wattage in the max watt display field on the power tap? Or should this downloaded max. watts match the display? Thanks in advance for any comments.

  2. Alex, it was set to 2. I've changed it to 1 and I'll check it on the next ride. Thanks for the suggestion - it makes sense.

  3. Bike N Ski said:

    Alex, it was set to 2. I've changed it to 1 and I'll check it on the next ride. Thanks for the suggestion - it makes sense.

    Have another crack at it and let us know.

  4. Bike N Ski said:

    Alex, it was set to 2. I've changed it to 1 and I'll check it on the next ride. Thanks for the suggestion - it makes sense.


    Sorry for digging up this old thread, but did you guys figure this out? Mine was set at 5 for two months and I too have experienced the same sort of things where my peak watts on the computer does not correlate with what i see in Cycling peaks or on Power Agent. Also-at times I dont see on the graph what I know I did on the ride. Of course this applies mostly to short intensity stuff (under 1 minute efforts and max power).

    Thanks in advance,
    Ray

  5. rayhuang said:

    Sorry for digging up this old thread, but did you guys figure this out? Mine was set at 5 for two months and I too have experienced the same sort of things where my peak watts on the computer does not correlate with what i see in Cycling peaks or on Power Agent. Also-at times I dont see on the graph what I know I did on the ride. Of course this applies mostly to short intensity stuff (under 1 minute efforts and max power).

    Thanks in advance,
    Ray

    What was set at 5? The CPU rolling average or the frequency of data sample capture?

    If you set it to capture data every 5 sec, it will discard all other data points in between, just recording every 4th one (at 1.26sec per data point). So if your power peak happened on a data point that isn't stored, that's why the difference.

    The CPU will still update the max power number on the CPU display no matter if that data point is stored for later download or not (since all it needs to know is if any instantaneous data point is higher than current max, and if so then update the max value for the CPU display).

  6. Alex Simmons said:

    What was set at 5? The CPU rolling average or the frequency of data sample capture?

    Frequency of data capture. I set it to 2 for the next ride.

    Thanks Alex,
    Ray

  7. rayhuang said:

    Frequency of data capture. I set it to 2 for the next ride.

    Why? Why not set it to 1? Is there any particular reason you have to set it to >1?

    Even if you change it from 5 to 2, there is still 50% chance for your download data to miss the maximum power you see on the computer.

    Ken

  8. sugaken said:

    Why? Why not set it to 1? Is there any particular reason you have to set it to >1?

    Even if you change it from 5 to 2, there is still 50% chance for your download data to miss the maximum power you see on the computer.

    Ken


    Good point-why didnt I set it to 1?!?!?!? My last download seemed to show more subtle variations in power so going from 5 to 2 seemed ot help-though I didnt do any short interval work.

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