In Welltory, you can take measurements of heart rate variability (HRV) with your smartphone camera, a heart rate monitor, or Apple Watch. Note that HRV measurement is not an electrocardiogram (ECG) recording, and it can't be used as a substitute for ECG or a medical check-up.

However, Welltory's HRV measurement accuracy is on par with ECG monitors, according to the results of this study published by Elsevier.

With no external devices connected, camera measurement will be set by default. Otherwise, Welltory will remember the last device you used. To switch back to the camera, head to Menu → Settings → Measurement Device.

If your phone camera has a green connected status, it will be used to take measurements.

To take an accurate camera measurement:

  • Make sure your phone has a flashlight.

  • Put your finger so that it covers both the camera and the flashlight.

  • Don’t press too tightly.

  • Don’t move your finger. Our algorithm analyzes the images it gets from the camera. Any movements can distort them.

  • Always use the same finger of the same hand.

Learn more on how to take an accurate measurement.

Note: With some phones, the flashlight may get too hot and even burn. If so, hold your finger 2–3 mm away from it. Make sure your finger still covers the camera.

How it works

We use an optical method called photoplethysmography (PPG). It measures changes in the volume of blood in vessels with a light source and a photodetector.

These changes are caused by the beating of your heart. We detect them by illuminating your finger with a flashlight and measuring the amount of light absorbed using camera images.

When your heart contracts, capillaries in your fingertip are full of blood — more light is absorbed, and the image becomes darker. When your heart expands, there is less blood in your capillaries — less light is absorbed, and the image becomes brighter. Capturing these changes, our algorithm can analyze your heart rate.

Learn more on photoplethysmography.

My smartphone has multiple cameras. How do I know my finger is on the right one?

When the measurement starts, you’ll see the image from the relevant camera on your phone’s screen. If the screen is bright red (due to the flashlight illuminating your capillaries), you’re good to go. If the screen shows your surroundings, your finger is on the wrong camera. Try putting it on each camera one by one until you see a red screen.

Note: With an iPhone X measurement, your finger should cover the bottom telephoto camera and the flashlight.

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