Downloaded data and PT display don't jive.

Discussion in 'Power Training' started by tonyzackery, Jan 11, 2010.

  1. tonyzackery

    tonyzackery Well-Known Member

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    Did a search for similar issues and found nothing. My display unit will show 'X' for max wattage and the downloaded max wattage in Power Agent will be lower than 'X'...Anybody know what's up with this??
     
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  2. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Any chance your PT recording interval is set to something longer than the minimum?

    -Dave
     
  3. tonyzackery

    tonyzackery Well-Known Member

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    Yes. I think I set it to 5secs awhile back.
     
  4. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Yep, that'd do it. The CPU displayed peak is at the hub sampling rate but the peak in your files would represent the best 5 second average power.

    -Dave

    [edit] Actually I can't recall whether the PT averages samples at lower recording rates or simply drops samples in which case your recorded peak would actually be just one sample out of each 5 second block which 4 out of 5 times won't actually be the peak.
     
  5. tonyzackery

    tonyzackery Well-Known Member

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    Thank you Obi Wan...
     
  6. Alex Simmons

    Alex Simmons Member

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    The PT discards all data except one second of data every 5 seconds.
    5 sec recording interval is definitely not recommended and significantly compromises the data analysis. Even at 2-sec recording, it discards every other data point.
     
  7. tonyzackery

    tonyzackery Well-Known Member

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    And here I was thinking I needed the extra long recording time afforded by the longer sampling rates. Heck, I download the thing after almost every ride as it stands anyway...I've switched the sampling rate back already...
     
  8. Alex Simmons

    Alex Simmons Member

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    Yeah - it's not a very smart "feature" of the cervo CPU. It would have been better had it simply averaged the previous 5 seconds and stored that but alas, no.

    FWIW - at 2 sec "sampling", the data isn't usually too bad (e.g. it wouldn't normally have a large impact on calculation of average and normalised power), but beyond that and I would take it with a grain of salt.
     
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