Powertap and cyclingpeak issue

Discussion in 'Power Training' started by SolarEnergy, Apr 24, 2006.

  1. SolarEnergy

    SolarEnergy New Member

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    Hi

    I was quietly cruising yesterday on my trainer (in ergo mode at fix power). I didn't anything wrong on my powertap computer display while riding.

    When I downloaded the data in cyclingpeak though, there was a lot of powervalues well over 1000w.

    1) was I sleeping while riding? Could it be that the display showed those high numbers and I didn't notice?

    2) could it be that cycling peak had problem with coma separated file or something?

    Also, I was wondering. While you ride at constant power, or at least when you try to do so, what is the typical variation of power that you see? For me, it's at least 15watts. Eg, actual power will go from 190 up to 204, then 195 then 190 then 205 then 195 then 201 then 188 then 206. It fluctuates every 2 or 3 seconds or so.

    Thanks
     
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  2. acoggan

    acoggan Member

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    With the PowerTap, the data that are written to memory are different from what are shown on the display. Moreover, the display provides a rolling average over some X seconds, where X will (can) depend on which computer you're using (i.e., PowerTap vs. PowerTap Pro) and how it is configured. So, the fact that you didn't see any 1000+ W spikes while riding doesn't mean that they didn't occur...and you can trust CyclingPeaks to faithfully represent what is stored in memory, warts and all (with the caveat that CyclingPeaks doesn't recognize any power value >2046 W).

    As for the "typical" variation, with the PowerTap this will depend in part on your cadence: since the PowerTap calculates power every 1.26 s, each data point will usually represent power over some non-integer number of pedal cycles. OTOH, pedal at, e.g., 95.2 rpm, and your power will appear much smoother.
     
  3. peterpen

    peterpen New Member

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    Sounds like some sort of interference/ PT problem to me - you'd know if you were putting out 1000w.

    re: typical variation of power, I haven't noticed such a large fluctuation, especially if I'm on a steady grade, rollers, or trainer. How fast do you have your display set? ie, 1",2", 5" ? This might acct for the big jumps.
     
  4. SolarEnergy

    SolarEnergy New Member

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    Thanks guys. I have a pt sl (the older generation though, not the wireless one).

    I think I left the default values. What would be the ideal setup if I want smoother power reading and recording?

    Andy, my typical cadence is between 98 and 104 rpm.

    Peterpen, you're right, I didn't generate 1000w during this workout, not even half of it. I'd expect interference to show on the display as well though. That confuses me a bit.

    Should I set the refreshing rate at 3sec for both the display and the recording? The longer the rate, the smoother power is, is that is? If it's the case, what about 5 or 10 seconds?

    Also, I have an other little one. Do you guys use the interval feature. Let's say I need to stop for a fuel refill, between two segments, how do I pause my workout?
     
  5. frenchyge

    frenchyge New Member

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    Setup will not affect the recording, only the display. The recording will be the 1.26-sec values, and that cannot be changed.

    The averaging interval for the display is a bit of a compromise between jumpiness and responsiveness (ie, during an intentional change in power). I find that 3-seconds works for me. During a steady-power effort I'll still see the display swing from just below to just above my target power, so I switch to average power (rather than instantaneous) after a couple minutes into an interval. That removes any temptation to adjust my effort based on the changing display values.

    No need to pause the unit if you're just taking a brief stop. The unit will sleep within a few seconds of the wheel stopping, and a single button push will wake everything back up as soon as you're ready to continue. It will continue recording right where it left off, and the CP graph display will show a short break in the data stream.

    I do use the interval function as a way to focus on a particular segment of a ride, such as when I want to watch my average power for a certain length of time or distance. I also use it to set a marker for post-ride analysis, such as to distinguish the warm-up period from the start of a race, etc.
     
  6. SolarEnergy

    SolarEnergy New Member

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    A bit confused here Frenchyge,
    There's just a minor detail I am missing here.

    When I look at a data file at the moment, I see that it recorded the data at every single second. If I remember correctly, this can be changed so the data will be recorded every 2-3-5-10-30 seconds :confused:

    Thanks, I'll try every 3

    I couldn't find a way to "reset" the average value when switching to a second interval.

    In other words, suppose I go 30m at 190w, then I want to follow my avg power for a 60min segment, I hit both buttons, that switches the interval number from 1 to 2. Fine.

    But the avg values displayed on the first line of the computer display, namely power, will continue showing the avg from the begining of the workout. To see the avg, I need to hold the select button until a little "m" appears besides the interval number, but is this information static or dynamic?

    Thanks a lot Frenchyge, that'll make me save some time.
     
  7. jetnjeff

    jetnjeff New Member

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    Press and hold the Mode button for 2 seconds to switch between shoing the entire ride and the current interval (with out the"M") Previous intervals will be staic and the current interval will be dynamic and be chaning as you look at it with or with out the "M" This is how the Pro works. I belive the standard and Pro show this same step in the manual.
     
  8. frenchyge

    frenchyge New Member

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    Doh! I mis-spoke. :eek: You can change the recording interval as you say. That's only necessary for very long rides where the 1-sec recording will exceed the on-board memory of the computer -- about 7.5 hrs for a new PT system, if I remember correctly.

    The main point is that the recording interval and display interval are independent. Changing the recording interval only affects the amount of ride time that can be recorded, and the post-ride power graph displayed on the PC.

    Jetnjeff answered the question about the interval function. Hold "Mode" for 2 seconds to see stats on the current interval only. Hitting both buttons to set a new interval will reset the time/dist/av. pwr-spd-HR/etc to zero when in that mode.
     
  9. SolarEnergy

    SolarEnergy New Member

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  10. SolarEnergy

    SolarEnergy New Member

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    I have maybe one more.

    Is cyclingpeaks odbc compliant or something?

    Can I get rid of that interference, by maybe replacing everything that's over 500w by the the same value read few seconds before?

    Or does it contain any correction features to address garbage data?

    And how do you use cyclingpeaks as a database. Can I sort my work by day, by week, by month?

    In other words, the summary page displays information about last 28 days. Are these header records containing summarized data, or are these resultsets based on some queries over a database?
     
  11. grom

    grom New Member

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    maybe you need to zero torque your powertap
     
  12. SolarEnergy

    SolarEnergy New Member

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    I did. But thanks anyway :)
     
  13. Flatscan

    Flatscan New Member

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    You can use View->Raw Data Grid to edit data manually. I think the cursor position is carried over from the graph, so you can place it near the spike, then switch and edit. Alternately, you can export the file and edit in plain text or in Excel.
     
  14. SolarEnergy

    SolarEnergy New Member

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    Can we reimport it you think?
     
  15. jetnjeff

    jetnjeff New Member

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    Do this with the "123" Anything you have the "EYE" on will be high lighted.

    I have not figured out how to copy this into Excel yet.

    Pointers welcome.
     
  16. jetnjeff

    jetnjeff New Member

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    Figured it out. Go to Excel got to the folder you saved the TXT file and open it and use Fixed Width delineation. make sure the data important data is in columns and delete the top few rows, once in Excel.
     
  17. Blackie

    Blackie New Member

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    Hi, this seems related so I thought I'd ask you guys. I did a crit today, and cycling peaks says the avg W was 202W, NP 265W. Yet my power tap SL says average W was 250W. Is this because I had the averaging set to 3sec (the recording was set to 1sec)?Thanks.
     
  18. JohnMeyers

    JohnMeyers New Member

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    You probably have you PT set to not record zeroes.
     
  19. RapDaddyo

    RapDaddyo Active Member

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    Sure, you can import or re-import a PT CSV file so long as it meets the CP requirements (e.g., data observations every 1.26 seconds). In fact, you can create a CSV file outside of CP and import it (e.g., a non-PT ride).
     
  20. SolarEnergy

    SolarEnergy New Member

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    Yeah but I mean can I re-import it to over-write an existing segment?

    And also.

    If I set the recording interval to 10, or even 30 seconds (instead of the default which is 1 second). Is it the average power over 10 seconds that is getting posted to the file, or is it one picture of the power readout every 10 seconds that's getting stored?
     
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