questions about Powertap SL

Discussion in 'Power Training' started by frenk, May 5, 2006.

  1. frenk

    frenk New Member

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    Hi all,

    After almost two years of trying to justify a powermeter I finally decided that I don't need to justify it, so I got a powertap sl :D

    The device is GREAT and so is cyclingpeaks (as a software engineer I say it's one of the most impressive sw I've seen lately).

    I have a couple of questions. First, I usually download the data after the ride, then I press and hold the two buttons until "clear", then press mode.
    So I start from zero on the next ride.
    But what if I don't download the data for a couple of rides? Distance, time, etc. will continue from where it left the day before?
    I'd like to reset everything but don't clear the memory.

    Second question: yesterday I did some sprints and the cpu shows a max power of 1999 W :eek: . Now this would be very cool but I'm not sure this data is real...
    Cyclingpeaks shows a max of 1254 W (5s and 10s is about 1150).
    Is it possible that there was an interference at some point that caused the very high reading?
    Or it is possible that for a very short amount of time --shorter than the recording interval (1s)-- I put out such a huge power?

    Thanks,

    Francesco
     
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  2. Alex Simmons

    Alex Simmons Member

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    CP will recognise the download as separate ride files that you can then drag into the calendar on the day you did them. Just do it once and you will see - it works fine.
    Most likely, I have seen this once, right before I started a ride. Not sure what caused it but I left it there caused it looked cool for an hour or so!

    Perhaps you could, I don't know, but the PT would not record it as such. It needs 1.26 seconds of hub data (sampled at 60Hz) to record one data point, which would be an average value for that entire 1.26 secs.
     
  3. RapDaddyo

    RapDaddyo Active Member

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    You can usually figure out whether a max power observation is an anomaly by looking at the data before and after. Watts, speed and torque all move together, so if you see a one observation spike you know it's bad data (e.g., 25mph w/ a 40mph spike). If it's real, you will see it from an overview of what's going on in the ride during a 15 or 30 second duration before and after the observation in question. A lot of the max power numbers occur from a standing start, which are only interesting if your event includes standing starts.
     
  4. Spunout

    Spunout New Member

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    Advance to the next interval and your display will be reset. But the earlier data is still in the PT under the previous interval(s).
     
  5. frenk

    frenk New Member

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    Thanks, that's it.
    OTOH does this mean that when I do an interval I won't be able to see the data of the whole ride anymore?
     
  6. Woofer

    Woofer New Member

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    Simply hold down the button again until it switches the CPU from interval mode to full ride mode. You can switch back and forth as many times as you wish.
     
  7. Spunout

    Spunout New Member

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    OP, you can also go into interval memory mode and view the stats on all previous intervals.

    Anyways, hit a new interval every day and you'll be starting over without losing data.
     
  8. SolarEnergy

    SolarEnergy New Member

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    I must admit that they built a very nice and interactive set of graphs, with left and right clicks and drags and stuff. There's a lot of work in it.

    Don't hesitate to play with these graphs. You can create your own by clicking on the option little button (top right corner).

    I had this issue (and some other issues too). But I used to get more than one sporadic, random >1000watts readout.

    I found out that it was because I was using the original USB Serial port driver that comes with Powertap CD, on an XP machine. If it's your case, be very careful, it generates very mean bugs.

    I forgot what the url was, but if you have a driver problem just call Saris and ask for the url to get the latest driver.
     
  9. velomanct

    velomanct New Member

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    I've seen some max readings of something like 5345w in the downloaded view, after a rainy ride! Max speed was 346mph too. Man I wish that was real, lol.

    I also have had a false max reading during a sprint, which pushed up my peak about 200watts. It's easy to spot if you look closely.
     
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