I didn't know a better place to ask this, so here it goes. For activity trackers, Fitbit has the Charge HR with an optical heart rate monitor, while Jawbone has the UP3 with a bioimpedance sensor for heart rate.
Can you please explain the differences between the two. Also, diagrams would make it more understandable.
Info about optical sensor: electronicdesign.com/displays/build-your-own-optical-heart-rate-sensor Also, are any diagrams from here relevant?
On Jawbone's blog, there is some info:
Bioimpedance measures the resistance of body tissue to tiny electric current to enable the capture of a wide range of physiological signals including your heart rate. If you've ever measured your body composition such as fat content, this is very similar. Our choice to use bioimpedance technology sets us apart in three key ways:
Battery life. Because bioimpedance requires significantly less power compared to optical sensors for same level of accuracy, we can deliver a smaller form factor and longer battery life Physiological signals. A single platform utilizing bioimpedance sensors captures a wide range of signals: heart rate, respiration rate and galvanic skin response (commonly known as skin conductance) Updatable technology. Given the versatility of the sensor platform, we are able to (and we will) unlock exciting new features with a simple, free, over-the-air firmware updates in the coming months