Guides
Measurement, not marketing. How to find out what your own sensors actually do — and how to read the numbers without kidding yourself.
How to bench two heart-rate sensors against each other
Wear a chest strap and a watch at once, stream both into one browser tab, and measure the disagreement directly. The full procedure, what bias, MAE, limits of agreement and sensor lag each tell you, and the five mistakes that quietly invalidate a run.
Polar H10 vs Fitbit: HRV accuracy, measured
Three minutes, both sensors on one body. Heart rate agreed within 5 bpm 94% of the time. HRV came out at 67.3 ms against 6.9 ms — and the reason is more interesting than a bad number.
Measure it yourself
HRV Dojo runs entirely in the browser on real sensor data — live HRV, ECG capture, breathing coherence, readiness, and a two-sensor bench. No account, nothing uploaded.
Open HRV Dojo