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Posts tagged: Motion Artifacts

2 posts found

A person sleeping on their side with a smart ring on their finger, illustrating how body position compresses the finger against a pillow or mattress
PpgAccuracySleep

Why Your Smart Ring's Nighttime Data Is a Lie: The Sleep Position Problem Nobody Mentions

Your smart ring's PPG sensor assumes your finger is at heart level with unrestricted blood flow. When you sleep on your side, neither of those things is true. Here is what the data actually looks like.

James Hoffmann James Hoffmann
Jun 21, 2026 1 min read
An oscilloscope display showing a clean waveform, representing the textbook PPG signal that smart rings almost never actually capture during motion
PpgHeart RateSensors

What Your Smart Ring's Heart Rate Data Looks Like After You Move: Motion Artifacts, Adaptive Filters, and the Signal You Never See

Your smart ring's PPG sensor produces clean heart rate data roughly 40 percent of the time. The other 60 percent is a signal that has been through an adaptive filter, and what comes out is a reconstruction. Here is what actually happens inside the chip when you wave your hand.

James Hoffmann James Hoffmann
Jun 18, 2026 1 min read