The optical sensors on the back of your smartwatch are not simply counting your pulse; they are executing a continuous, microscopic audit of your cardiovascular system. When you look at the metrics for your Heart Rate Variability (HRV) or your deep sleep architecture, you are looking at the output of a highly complex algorithmic translation. The device itself is not measuring electrical signals from your heart like an EKG in a hospital. It is using a technology called Photoplethysmography (PPG) to measure the physical volume of blood moving through your capillaries via light refraction. Here is the hardware science of how health wearables turn a glowing LED into high-resolution biological data. The Physics of Optical Blood Tracking The fundamental operating principle of PPG is based on light absorption. Blood is red because it reflects red light and naturally absorbs green light. When you strap a wearable to your wrist or slide a smart ring onto your finger, the device fires a high-i...
Nearly twenty years ago, I started a blog called The Path is Too Deep, a geeky reference to a rare computer error message. A great deal of life has happened since then, a life I would like to share. So, here again, are some random bits of unfiltered Chris.