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steve knight

macrumors 68030
Original poster
Jan 28, 2009
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I had to change my watch over to to my right wrist because of a wrist brace and it has a tattoo and the watch keeps locking.
image1.jpeg
 
I think tattoos are a known limitation of the Appel watch. It uses LEDs and the pigment in the ink absorbs the light differently to what it is expecting.
You can turn the lock off which will solve the issue although it will disable some features.
 
I am enrolled in that heart study. I will try the sticker. this thing made the change happen. if I can keep it on the other side of my wrist bone it works. may have to get one of those sport loops to keep it in place. IMG_0717.jpg
 
It uses LEDs and the pigment in the ink absorbs the light differently to what it is expecting..

This is incorrect. Its not absorbtion, Its reflection based. 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.
 
This is incorrect. Its not absorbtion, Its reflection based. 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.
I’m going to straight up apologize for the useless post that follows this message.

Omg! Keep talking nerdy tech to me!

I’m sorry. I had to.
 
This is incorrect. Its not absorbtion, Its reflection based. 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.

So what happens to the light energy that isn’t reflected back?
 
So what happens to the light energy that isn’t reflected back?

I explained this. Its being blocked by the dark ink. The reflection is being directly blocked, which can’t achieve a proper reading or accurate measurement, nothing specifically has to “Happen”, Because of said reasons. It negates the reflectivity and measurements are not quantified or read properly. Any light is essentially is being “Un-used.”
 
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I explained this. Its being blocked by the dark ink. The reflection is being directly blocked, which can’t achieve a proper reading or accurate measurement, nothing specifically has to “Happen”, Because of said reasons. It negates the reflectivity and measurements are not quantified or read properly. Any light is essentially is being “Un-used.”

Dark colours absorb light hence why it isn’t reflected.
 
Dark colours absorb light hence why it isn’t reflected.

This is what you originally quoted:

It uses LEDs and the pigment in the ink absorbs the light differently to what it is expecting..”

Which is completely false, its NOT absorbed and you’re spreading misinformation . It was explained to you three times now that you don’t understand the sensor readings and the measurements is actually trying to read from the penetration of the skin which is being blocked by the reflection the ink from the actual contact point, it’s not absorbed. Please research photoplethysmogpahy versus arguing something you don’t understand. Also, the light energy from reflected back from the photodiodes past penetration isn’t providing a reading after the Initial delay, its simply un-used. Nothing happens, which is why the watch won’t unlock or provide an accurate heart reading. Also, some ink isn’t as saturated, which the reflection is able to penetrate past, but other dark colored area’s is far more problematic.
 
This is what you originally quoted:

It uses LEDs and the pigment in the ink absorbs the light differently to what it is expecting..”

Which is completely false, its NOT absorbed and you’re spreading misinformation . It was explained to you three times now that you don’t understand the sensor readings and the measurements is actually trying to read from the penetration of the skin which is being blocked by the reflection the ink from the actual contact point, it’s not absorbed. Please research photoplethysmogpahy versus arguing something you don’t understand. Also, the light energy from reflected back from the photodiodes past penetration isn’t providing a reading after the Initial delay, its simply un-used. Nothing happens, which is why the watch won’t unlock or provide an accurate heart reading. Also, some ink isn’t as saturated, which the reflection is able to penetrate past, but other dark colored area’s is far more problematic.

So your telling me tattoos don’t absorb light? Interesting.
 
So your telling me tattoos don’t absorb light? Interesting.

Two things that are not mutually exclusive, in which case you don’t understand the context of the discussion, which was proven multiple times, yet you refute unrelated points already addressed.
 
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Two things that are not mutually exclusive, in which case you don’t understand the context of the discussion, which was proven multiple times, yet you refute unrelated points already addressed.

Reflected light and absorbed light are not unrelated though.
 
Good grief. We can argue over anything these days.

Off topic to the OP: Judging the looks of the tatoo, it is pretty dark.

I also had to move my AW to my right wrist as my left wrist has carpel.

Hope yours get well.
 
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I have two tattoos on my wrist area. with a small space separating the two. I can wear my watch in between the two and it works perfectly except for when the watch slips just a bit lower on my wrist. I had planned the original tattoo on my wrist with the idea that I could always hide it with a watch one day if I ever had to. That was 2010. Smart watches weren't a thing yet.
 
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The silicone disc did let the watch work but I could not get it to charge. Not that big of a deal. I got a sports loop to see if I could keep the watch on the other side of my wrist but it would slip after a bit.
 
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