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Heart rate is the most fundamental vital sign returned by the Neurofit Vitals SDK and also its most accurate one. During a 60-second scan the SDK captures a continuous photoplethysmography (PPG) signal from the rear camera — the subtle changes in light reflected by the fingertip as blood pulses through the capillaries — and uses peak detection across that waveform to compute the average number of beats per minute over the entire window. The result is a single Double value available the moment a scan completes with an accepted quality tier.

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How It Is Measured

The rear camera acts as an optical sensor: the user places a finger over the lens and flash, and the camera records tiny frame-to-frame brightness variations caused by pulsatile blood flow. The SDK extracts a clean PPG waveform from this video stream, identifies each cardiac cycle, and averages the resulting inter-beat intervals into a beats-per-minute figure. Because the measurement spans the full 60-second window rather than a short epoch, transient noise has minimal effect on the final value.

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Validated Accuracy

Neurofit Vitals heart rate was validated against the Polar H10 chest strap — the consumer gold-standard reference for beat-to-beat cardiac measurement — across a diverse participant sample.
A mean absolute error of 0.47 bpm and r = 0.999 place the SDK’s heart rate on par with dedicated optical heart rate monitors. For most consumer wellness applications, a ±1 bpm tolerance is more than sufficient.

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SDK Field Reference

Heart rate is exposed as a Double on the VitalsResult object returned after a successful scan. It is expressed in beats per minute (bpm) and is always populated when qualityTier is .accepted / QualityTier.ACCEPTED.

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Interpreting the Value

For healthy adults at rest, heart rate typically falls between 60 and 100 bpm. Values below 60 bpm (bradycardia) are common in trained athletes and are not inherently problematic. Values above 100 bpm at rest (tachycardia) can have many benign causes — caffeine, stress, dehydration — as well as clinical ones.The Neurofit Vitals SDK measures heart rate at the moment of the scan. Because heart rate responds quickly to posture, breathing, and activity, encourage users to sit quietly for at least 60 seconds before scanning to obtain a stable resting measurement.
Several environmental and behavioural factors can reduce signal quality and cause the SDK to return a lower-confidence or rejected result rather than an inaccurate one:
  • Motion: finger movement during the scan introduces artifact into the PPG waveform.
  • Pressure: pressing too hard or too lightly on the lens reduces perfusion signal quality.
  • Lighting: very bright ambient light can wash out the camera sensor.
  • Cold extremities: reduced peripheral blood flow in cold conditions weakens the PPG amplitude.
When any of these factors degrade the signal below acceptable thresholds, the SDK sets qualityTier to a non-accepted value and does not populate heartRate.
Neurofit Vitals is not a medical device. The heartRate value is intended for general wellness and fitness applications only, and must not be used for clinical diagnosis, treatment decisions, or monitoring of any medical condition.