Apple Watch and my tattoo..

Discussion in 'Apple Watch' started by kdw877, Jun 16, 2017.

  1. kdw877 macrumors newbie

    Joined:
    Feb 14, 2017
    #1
    so I have a black and grey sleeve tattoo, not solid lots of small details. I've tried the watch in both wrists and the heart rate sensor is pretty much identical on each wrist, the tattooed and the not tattooed. However, on the tattooed wrist it locks every time the screen goes off. On my untattooed arm, it doesn't lock unless I take it off. It seems odd since the heart rate is the same on each wrist but wrist detection trips?
     
  2. Relentless Power, Jun 16, 2017
    Last edited: Jun 18, 2017

    Relentless Power macrumors P6

    Relentless Power

    Joined:
    Jul 12, 2016
    #2
    The Watch senses when it's on your wrist. Regarding the tattoo, it's having difficulty to sense the wrist detection due to reflectivity. I have read where other forum members have had the same situation you have.
     
  3. infinitejest macrumors 6502

    infinitejest

    Joined:
    May 1, 2016
    Location:
    Orange County, CA
    #3
    Happens to me too as soon as the Watch slips down a bit.

    IMG_1575.JPG
     
  4. kdw877 thread starter macrumors newbie

    Joined:
    Feb 14, 2017
    #4
    It's so annoying because having to wear it on my right hand means everything I do on it is my left (wrong) hand. I might just wear it on left and turn off wrist detection. I hardly ever use Apple Pay on my phone even so I won't miss much
     
  5. infinitejest macrumors 6502

    infinitejest

    Joined:
    May 1, 2016
    Location:
    Orange County, CA
    #5
    Yeah, turning off wrist detection is probably the easiest way. However, I use the unlock my MacBook feature and that only works when wrist detection is turned on.
    I don't have much problem to keep it on the same spot on my wrist and when I'm running I wear it on my right arm.
     
  6. kdw877 thread starter macrumors newbie

    Joined:
    Feb 14, 2017
    #6
    Is the heart rate sensor still accurate on tattoo arm? Cos it seems to read the same when I switch it a couple times to test. Just wrist detection doesn't work so I'm not sure how it's getting the same heart rate still
     
  7. Newtons Apple Suspended

    Newtons Apple

    Joined:
    Mar 12, 2014
    Location:
    Jacksonville, Florida
    #7
    Might need to shave a little bit of that hair off you arm.
     
  8. kdw877 thread starter macrumors newbie

    Joined:
    Feb 14, 2017
    #8
    Haha I don't really have any, little blonde ones maybe
     
  9. Newtons Apple Suspended

    Newtons Apple

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    Mar 12, 2014
    Location:
    Jacksonville, Florida
    #9
    Sorry ment infinitegest.
     
  10. infinitejest macrumors 6502

    infinitejest

    Joined:
    May 1, 2016
    Location:
    Orange County, CA
    #10
    Yep, still accurate on the tattoo arm. Seems like they use different techniques to detect the wrist and to measure the heart rate.
     
  11. Cogsworth macrumors 6502

    Cogsworth

    Joined:
    Feb 7, 2015
    #11
    Huh so wrist detection works by shining light on the skin and measuring how much is reflected, so dark tattoos interfere with the reflection and cause wrist detection to fail.

    Must be a different technology than heart rate, since that uses visible green light and wrist detection uses invisible (infrared?) light.
     
  12. Relentless Power macrumors P6

    Relentless Power

    Joined:
    Jul 12, 2016
    #12
    The Apple Watch uses photoplethysmography, which essentially enables the rear LED sensors distribute light towards your skin and measure the skin, which immediately reflects back. If there is no reflection or little reflection, Passcode is engaged. Hence, dark tattoo's have very little reflection due to the dark ink.

    The other two sensors are illumination sensitive photodiodes, which detect reflected light from your arms blood vessels and as a the heart beat is happening, the blood flow is occurring and the green diodes absorb the light to distinguish between beats as the reflection differentiates.
     
  13. infinitejest macrumors 6502

    infinitejest

    Joined:
    May 1, 2016
    Location:
    Orange County, CA
    #13
    Thanks, well explained!
     

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