I'm trying to understand the methods smartwatches use to provide near‑real‑time heart‑rate data without a noticeable impact on battery life. Specifically, how do low‑power sensors, duty‑cycling, and on‑device processing combine to achieve this balance? Are there trade‑offs in accuracy versus power consumption that developers typically consider? Would love to hear explanations or references from anyone familiar with the architecture.
How do smartwatches track heart rate while keeping battery drain low?
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Smartwatches typically use a PPG sensor that pulses a low‑power LED for just a few milliseconds every 5–10 seconds, much like the intermittent sampling you see in Bluetooth chest‑strap monitors, and then run a tiny on‑device algorithm to smooth the values before sending them to the main processor. This duty‑cycling keeps battery use minimal, but it does mean rapid heart‑rate spikes can be slightly blurred compared to a continuously‑recording ECG strap.