Understanding the measurement duration

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Earlier versions of Shen AI required a 60-second measurement. Thanks to improvements in the SDK's signal processing pipeline, including a new multimodal sensing engine that combines remote photoplethysmography (rPPG) with remote ballistocardiography (rBCG), the standard measurement time has been reduced to 30 seconds while maintaining the same level of accuracy.

Today, the default measurement takes 30 seconds. During that time, the SDK continuously analyzes the physiological signal captured by the camera to estimate multiple vital signs and health insights from a single scan.

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What happens during the scan?

As soon as the measurement starts, the SDK begins analyzing subtle color changes in the face and micro-movements of the head caused by blood flow. Throughout the scan, it continuously evaluates signal quality and collects the data needed to estimate the requested measurements.

Not every metric requires the same amount of information. Some can be calculated from a relatively short signal, while others depend on observing physiological changes over a longer period.

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What appears first?

In the default measurement experience, heart rate is typically the first metric displayed. It usually becomes available within about 5 seconds, giving users immediate feedback while the rest of the measurement continues.

The remaining vital signs and health insights are calculated after enough data has been collected and are presented when the measurement is complete.

Keep in mind that this describes the default Shen AI experience. If you're integrating the SDK into your own application, you can customize the measurement experience, so the timing and presentation of results may differ from the standard implementation.

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Can you customize the measurement experience?

Yes. The SDK allows you to tailor both the measurement flow and the user interface to match your product.

Depending on your implementation, you can configure aspects such as:

- which metrics are shown,
- whether intermediate results are displayed,
- the measurement duration,
- the final results screen.

For more information, see Customizing the measurement experience.

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What happens if the scan is interrupted?

A measurement must collect enough usable data before the SDK can calculate the final results.

If the scan is interrupted, for example because the user moves away from the camera, the face is no longer visible, or the session is stopped early, the measurement may not complete successfully and some or all results may not be returned.

Your application should handle these situations by prompting the user to try the measurement again.

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Best practices for a successful measurement

To achieve the best results, encourage users to:

- remain still throughout the measurement,
- keep their face centered within the frame,
- avoid talking or making large facial movements,
- use even, well-lit conditions,
- begin the scan only when they are ready to remain still for the full measurement.

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These recommendations help the SDK capture a stable physiological signal and improve measurement quality.

If you're providing guidance directly to end users, you can also share the How to use Shen AI guide. Check the Preparing users for their first measurement article to learn more about user onboarding.

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