SRPhotoplethysmogramOpticalSample
A data sample from the photoplethysmogram (PPG) optical sensor.
Declaration
class SRPhotoplethysmogramOpticalSampleOverview
To get the PPG waveform, use the normalizedReflectance property. Apple Watch uses an arrangement of emitters and photodiodes to measure the PPG waveform.
Interpret second-generation PPG sensors data
Second-generation optical heart sensors, in Apple Watch 4, 5, SE 3 and SE models, use green or infrared (IR) LED lights paired with light-sensitive photodiodes.
The active photodiode’s indices show which photodiode or combination of photodiodes the Apple Watch uses. The light-sensitive photodiodes have different arrangements between the Apple Watch models:
For the second-generation sensors, the mapping of the optical heart sensor (SE, Series 4 and 5) emitter is:
Emitter index | LED arrangement |
|---|---|
0 | 0, Infrared (940 nm) |
1 | 1, Infrared (940 nm) |
2 | 2, Green (525 nm) |
3 | 3, Green (525 nm) |
4 | 4, Green (525 nm) |
5 | 5, Green (525 nm) |
Interpret third-generation PPG sensors
Third-generation optical heart sensor, in Apple Watch Series 6 and later, plus Apple Watch Ultra and Ultra 2, use an additional red LED with a different arrangement of emitters and photodiodes than the second-generation PPG sensors. The active photodiodes indices show which photodiode or combination of photodiodes the Apple Watch uses.
[Image]
For the third-generation sensors, the mapping of the optical heart sensor (Series 6, 7, 8, 9, Ultra, and Ultra 2) emitter is:
Emitter index | LED arrangement |
|---|---|
0 | 0, Infrared (850 nm) |
1 | 1, Infrared (850 nm) |
2 | 2, Infrared (850 nm) |
3 | 3, Infrared (850 nm) |
4 | 4, Infrared (940 nm) |
5 | 5, Red (660 nm) |
6 | 6, Red (660 nm) |
7 | 7, Red (660 nm) |
8 | 8, Red (660 nm) |
9 | 9, Green (525 nm) |
10 | 10, Green (525 nm) |
11 | 11, Green (525 nm) |
12 | 12, Green (525 nm) |