HRV describes variation in the time between detected heart beats. It is not the same thing as heart rate, and a “higher is always better” rule misses most of the useful context.
Three labels you may see
SDNN summarises overall variation between beat intervals in a session. RMSSD focuses on shorter, successive changes. pNN50 is the percentage of successive intervals that differ by more than 50 milliseconds.
Why the values do not appear after every check-in
HRV needs cleaner beat-to-beat timing than a basic pulse value. If the camera signal contains movement, unstable light or uncertain peaks, Cardiom may save heart rate without presenting HRV details. Missing data is better than false precision.
Compare with yourself
Device, posture, breathing, time and measurement duration can all affect short HRV sessions. The most useful comparison is usually your own repeated routine using the same method.
- Measure at a similar time when practical.
- Sit still and breathe naturally.
- Compare Finger and Face trends separately.
- Focus on broader direction, not one unusual session.
Consumer camera HRV is personal wellness context. Clinical HRV assessment may use longer recordings, controlled protocols and medical-grade sensors.