Tennis Warehouse: Zepp Tennis Sensor Playtest

Discussion in 'Racquets' started by TW Staff, Feb 3, 2014.

  1. julian

    julian Hall of Fame

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    Last edited by a moderator: Feb 17, 2014
    #51
  2. gzhpcu

    gzhpcu Professional

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    corrected...
     
    #52
  3. palmerop

    palmerop Rookie

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    Fortunately I'm playing the Babolat pure drive play...

     
    #53
  4. Shroud

    Shroud Hall of Fame

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    Why is the power too low? Because you have some ego number in mind? The value of the number is how it changes in each session, not some relative scale. IMHO if the pros are 100 then 13 is probably accurate based on the vid. though I bet Zepp learns from these posts and inflates so the rec player "feels better".
     
    #54
  5. gzhpcu

    gzhpcu Professional

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    I sent the videos to Zepp support and they wrote back that the values are way too low. I would prefer an absolute power figure being used. Zepp support told me that the sensor seems to be faulty and they would send me a new one.

    But according to you, pros hit ten times harder than this:
    https://www.youtube.com/watch?v=KuBvWtUYk_4
     
    Last edited: Feb 15, 2014
    #55
  6. Shroud

    Shroud Hall of Fame

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    See they ARE learning!

    Maybe it is defective, but compared to this video, yes:

    https://www.youtube.com/watch?v=jzb_GbnMnnM

    10x would be over the 100 power level but I think you can see the difference in the vids.
     
    #56
  7. gzhpcu

    gzhpcu Professional

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    Certainly a twenty year old pro hits much harder than a 69 year old amateur. But do you understand what 10 times harder means? And no, I am not in a dick-measuring contest.
     
    #57
  8. Shroud

    Shroud Hall of Fame

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    Well we are assuming some things, like that its some sort of linear progression. Maybe its some inverse logarithmic function or maybe its just tracking RHS and perhaps 7x (13 to 100 is about 7x)RHS doesnt lead to 7x ball velocity, etc.

    Even if we knew I can't see how useful an absolute number would be, though the relative numbers between session or after starting new technics, weight training, etc. would have value.

    Anyhow for 69 you are in great shape and you should market your secret.
     
    #58
  9. julian

    julian Hall of Fame

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    Rhs

    How do you know whether it is really RHS?
    There is a second option
    Julian W.Mielniczuk
     
    Last edited by a moderator: Feb 17, 2014
    #59
  10. julian

    julian Hall of Fame

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    220 kms per hour quoted for a competing vendor

    220 kms per hour as a speed of an outgoing ball quoted as a max value for
    a competing vendor
    Julian W.Mielniczuk
    Babolat Team member
     
    Last edited: Feb 16, 2014
    #60
  11. gzhpcu

    gzhpcu Professional

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    That is the problem: no information on how to interpret the metrics or how they are derived.
     
    #61
  12. gzhpcu

    gzhpcu Professional

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    I still think there is a race to bring a product on the market (to get an early ROI for further development?) and immature products are coming out. Had I known, I would have waited 6 months... It was just the novelty effect that lured me...
     
    #62
  13. julian

    julian Hall of Fame

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    Channels of communication

    Sir,
    I believe some channels of communications should be open.
    Chris Edwards is an excellent source of info-
    he tried both sensors.
    He is getting consistent power numbers for both sensors.
    I have posted some questions for Chris Edwards in the section entitled
    TW Questions/Comments.
    He responded to first three questions.
    He promised a TW review shortly after March 17th (which is not very far away).
    My experience with sensors as described above is limited to avionics.
    I have checked that there are no Customer Reviews posted by TW US
    for a Zepp Sensor.
    I have looked for independent reviews of a Zepp sensors in Europe
    and I cannot find them.

    There is a manual for a Zepp sensor but it does NOT answer all of my questions.
    There are tutorials as well.
    I assume you know all tutorials already.

    The max numbers for forehands from the ATP tour are in the range 100-124 mph
    The link below
    https://www.google.com/#q=Landlinger+tennis
    provides a list of publications on forehand.
    The max numbers for forehands for elite Austrian players are below 60 mph,if my memory serves me well.
    I have checked corresponding reviews for a Zepp golf sensor
    http://www.zepp.com/golfsense/reviews/
    There are three or four threads with a discussion about a Zepp sensor.
    Please let me know which posts/threads of mine are of low technical quality and I will put an effort to improve them.
    respectfully.
    Julian W.Mielniczuk
     
    Last edited by a moderator: Feb 17, 2014
    #63
  14. Shroud

    Shroud Hall of Fame

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    I don't, and I did use the word MAYBE a few times.

    Do you know what it is really measuring?
     
    Last edited by a moderator: Feb 17, 2014
    #64
  15. palmerop

    palmerop Rookie

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    Strongest forehand I got was 61. Strongest backhand was 63.

     
    Last edited by a moderator: Feb 17, 2014
    #65
  16. palmerop

    palmerop Rookie

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    I clocked a 71 serve that was definitely an outlier.
     
    #66
  17. gzhpcu

    gzhpcu Professional

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    BTW: the Zepp support team wrote me that:

    The other issue I had was that I kept getting other user's data on the iPhone app instead of mine. This was finally resolved.

    I should be getting a new Zepp sensor by midweek....
     
    #67
  18. julian

    julian Hall of Fame

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    110 miles per hour?

    110 miles per hour if I understand the max value issue correctly.
    Pretty impressive
    Julian w.mielniczuk
     
    Last edited by a moderator: Feb 17, 2014
    #68
  19. palmerop

    palmerop Rookie

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    156 km/h racquet head speed... I'm not sure I serve that fast usually.
     
    #69
  20. palmerop

    palmerop Rookie

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    As I said my average power is well below 50 percent normally.

     
    #70
  21. julian

    julian Hall of Fame

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    110 miles per hour

    110 miles per hour was referring to an outgoing ball speed
     
    #71
  22. julian

    julian Hall of Fame

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    Did you get your new sensor?

    Did you get your new sensor?
     
    #72
  23. julian

    julian Hall of Fame

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    Do you see any areas for improvement?

    Do you see any areas to improve your serve?
    Did you try to combine/cross reference your sensor data with videos of your strokes?
     
    Last edited: Feb 18, 2014
    #73
  24. gzhpcu

    gzhpcu Professional

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    Arrives by Wednesday afternoon...
     
    #74
  25. palmerop

    palmerop Rookie

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    on the serve racquet head speed and swing speed are the same aren't they?
     
    #75
  26. palmerop

    palmerop Rookie

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    I've been mostly looking at the impact locator. I've seen some big improvements there. Also, I look at hitting more backhands and more topspin backhands. The one thing I don't care too much about is increasing my power... I'm very far from that unfortunately.
     
    Last edited: Feb 18, 2014
    #76
  27. julian

    julian Hall of Fame

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    Two different enities

    Two different entities are:
    A racket head speed and an outgoing ball speed.
    They are at the ratio 7 to 10 for forehand.
    Probably a similar ratio for a serve.
    Please let me know whether my explanation is clear enough
     
    #77
  28. julian

    julian Hall of Fame

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    Impact locator

    Please elaborate whether an impact locator improved your serve.
    Thank you
     
    #78
  29. julian

    julian Hall of Fame

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    I do not understand the last sentence

    I do not understand your last sentence.
    Please elaborate.
    Your power numbers for forehand are very good.
    Thank you.
    Julian
     
    #79
  30. julian

    julian Hall of Fame

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    Swing speed

    I do not know what a swing speed is
     
    #80
  31. julian

    julian Hall of Fame

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    What strings?

    What strnings and which tension (ball park)?
     
    #81
  32. palmerop

    palmerop Rookie

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    I'm using rpm blast at 48 lbs. I think the Babolat sensors only measure the swing speed but don't give you a measure of the outgoing ball speed. I'm saying that because Babolat official says that string type/tension or lead tape won't affect the measurement. However, I don't know this for sure.

    I'm wondering whether this topic should be discussed in a Babolat play thread and not here but I'll first answer the other questions you asked me. I already gave the answer to some of your questions in the Babolat play playtest thread btw.
     
    #82
  33. palmerop

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    When I wrote swing speed I meant outgoing ball speed. I am pretty sure the ratio is not the same for forehand and serve. On serve you hit a static ball that has no incoming speed.
     
    #83
  34. palmerop

    palmerop Rookie

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    I'm just not trying to hit harder or heavier balls. I've improved my consistency by hitting less off center shots. I discussed this in the Babolat play playtest thread. Mostly on my backhand and then on my forehand. I got some tips here on tt on how to do that btw.
     
    #84
  35. palmerop

    palmerop Rookie

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    i meant racquet head speed/outgoing ball speed. Sorry about that.
     
    #85
  36. magmasilk

    magmasilk New User

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    Not an official tester, but received my zepp. Have the testers got theirs yet?

    So far one session. Seemed to collect accurate info. Not obvious since no minute by minute data similar to fitbit/jawbone app. At least start and end time would be nice. Also my session was recorded on a random day. Not sure how it's supposed to track date/time, but didn't work so far. Anyone have this happen?

    Comfort-wise I didn't notice weight or impact to grip. I put it under my overgrip. Also I don't hold at the end of the grip.

    * edit *

    Resynced and the data includes more realistic power and duration and date!
     
    Last edited: Feb 19, 2014
    #86
  37. julian

    julian Hall of Fame

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    A new thread entitled "sensors"

    I will move some questions to to the thread entitled "sensors"
     
    #87
  38. julian

    julian Hall of Fame

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    I will respond in the thread entitled "sensors"

    I will respond in the thread entitled "sensors"
     
    #88
  39. gzhpcu

    gzhpcu Professional

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    Zepp sensor finally works for me! Playing on clay courts in lugano
    Gave very low figures, trained this week in dubai on hard courts
    And now results are good: serve 62 average, 79 max. Forehand 50 average, 60 max, backhand: 42 average, 70 max, now
    I wonder why does the surface make such
    A big difference? If explainable. Zepp should add a parameter for surface type.
     
    #89
  40. julian

    julian Hall of Fame

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    Hard surface and high temperature

    Hard surface and high temperature did provide a higher speed of
    an incoming ball (for forehand and backhand).
     
    #90
  41. gzhpcu

    gzhpcu Professional

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    Don't think so. Played with 20 C in Lugano (indoors) and with 24 C (early morning in Dubai). Moreover, it was a slow hardcourt. Noticed no difference in speed. And anyway, it could not make a difference of a factor of 4.
     
    #91
  42. julian

    julian Hall of Fame

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    Hard courts in Dubai

    Hard courts in Dubai accumulate heat during the day.
    Layer number 6 or number 5 is generally a rubber.

    A quality and a weight of balls could matter as well
    Even a difference between hard surface balls in Dubai and clay balls
    in Lugano could matter
     
    #92
  43. gzhpcu

    gzhpcu Professional

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    What does the Zepp sensor measure is the question? Swing? Impact?
     
    #93
  44. gzhpcu

    gzhpcu Professional

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    If it matters that much, then these must be parameters to be entered when configuring the Zepp app.
     
    #94
  45. gzhpcu

    gzhpcu Professional

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    The equation for momentum is: m(of tennis ball) x v(of tennis ball) + M(of racket) x V(of racket) = m x v' + M x V', v' and V' being the velocities after impact.

    Newton: At impact - The force of the ball on the racket is equal and opposite to the force of the racket on the ball.

    ma=MA

    So: m (mass of tennis ball) x a (acceleration of tennis ball) = M (mass of tennis racket) x A (acceleration of racket)

    a = v - v'
    A = V - V'

    The important factors are:
    - swing speed of racket
    - weight of racket
    - speed of ball before impact
    - weight of tennis ball

    Apart from my problems with the surface, shouldn't a configuration parameter also include weight of the racket for more accurate measurement?
     
    #95
  46. gzhpcu

    gzhpcu Professional

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    As I understand it:
    The Zepp sensor has two acceleration sensors using piezoelectric effect to detect acceleration and gyro sensor: detects angular velocity using the coriolis force.

    At impact with the ball, the racket rebounds slightly - this force can be calculated then from the resulting brief acceleration acceleration rebound value measured (and a default racket mass value).

    The gyro sensor detects the direction of movement at impact, so it knows what type of spin applies.
     
    #96
  47. julian

    julian Hall of Fame

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    Comparison with Sony

    Sony limits usage of their sensor to four models.
    To the best of my knowledge all four models have very close weights.
    So in the case of Sony there is no issue-see your last sentence.
    You may consider asking a Zepp support the question.
    Once more i find a conversation very useful.

    It provides an insight what sensors do well
     
    Last edited: Mar 3, 2014
    #97
  48. julian

    julian Hall of Fame

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    Regret

    The only thing to regret is that we did not do this analysis two months ago
     
    Last edited: Mar 3, 2014
    #98
  49. julian

    julian Hall of Fame

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    Swingweight

    I believe swing weight is an important parameter as well.
    The only problem is that it does not enter in an obvious way equations
    you posted above
     
    #99
  50. julian

    julian Hall of Fame

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    Ball machines

    Ball machines are recommended for testing sensors.
    If a ball machine has multiple speeds comparing results from a slowest
    to fastest gives some idea what a sensor can do for a given surface of courts
     
    Last edited: Mar 3, 2014

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