Apple details Watch Series 12 sensor with dual-zone ceramic to block optical cross-talk

Apple has for the first time described the ring-shaped health sensor in Apple Watch Series 12 and Ultra 4: eight LEDs, eight trapezoidal photodiodes around the perimeter, and a dual-injection zirconia ceramic that blocks light leaking between emitters and receivers. Background heart rate sampling now runs every five seconds instead of five minutes, though HRV accuracy remains unvalidated.

• Sensor uses 8 LEDs (4 green, 4 red/NIR) and 8 trapezoidal photodiodes in a ring
• Two zirconia formulations with different yttria levels are sintered into one ceramic part
• Background heart rate readings every 5 seconds, up from every 5 minutes
• HRV accuracy is not validated in the white paper