Can you tell me what's the difference of PPG bomb between b840 and b 810?

你能告诉我b840和B810的PPG炸弹有什么区别吗？

We won't get into too much detail as to how it works, but by emitting green light, the watch's optical PPG sensor tracks blood circulation of your wrist, which outputs data to measure a little thing called your heart rate.

我们不会详细介绍它是如何工作的，但是通过发出绿光，手表的光学 PPG 传感器跟踪你手腕的血液循环，输出数据来测量一个叫做心率的数据。