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How to measure heart rate and Spo2 levels on Samsung s9?

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  • 5 min read

Today’s smartphones can do many things, and if you own a Samsung flagship, you can measure your heart rate and oxygen saturation levels in the blink of an eye.

That said, most users are sceptical about measuring vitals using smartphones, as the accuracy of these results is questionable.

So in this article, we will be looking at how pulse oximeters work and the accuracy they offer when mounted on a smartphone. Thereafter we will be guiding you on how you can use the Samsung health app to measure your heart rate and oxygen saturation levels.

Samsung flagships starting from the Samsung S5 have an integrated pulse oximeter which enables devices to measure heart rate and oxygen saturation. That said, the Samsung S20 series does not have this sensor, and you can’t measure your oxygen saturation if you are using Samsungs’ latest flagships.

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How to calculate Spo2 and heart rate on Samsung smartphones?

Samsung makes things extremely easy when it comes to calculating Spo2 and heart rate levels. All you have to do is place your finger on the oximeter next to your camera, and the Samsung health app does the rest for you.

To calculate your Spo2 and heart rate follow the steps given

How to measure heart rate and Spo2 levels on Samsung s9?
  • Open the Samsung Health app on your smartphone.
  • Scroll down to Stress and click on Measure.
  • Place your finger on the oximeter next to the camera module and wait for the app to process data.
  • Save results with notes to monitor and stay on top of your health by clicking on the Save button.

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How does the pulse oximeter work on your Samsung devices?

The pulse oximeter on a Samsung device works on the same principle as any other oxygen saturation measuring device. The only difference is that this sensor is placed on the back of a mobile phone and is manufactured by Maxim Integrated.

Getting into the electronic side of things, a pulse oximeter sensor consists of two light-emitting diodes, one in the visible spectrum at 660 nanometers (Red light) and another in the infrared region at 910 nanometers. The device also has a photodiode which is used to analyse the reflected light signals.

Wavelength vs molar extinction coefficient (a measure of how strongly a substance absorbs light at a particular wavelength.). Inset Source: Wikimedia Commons

Now you might be wondering what a set of LEDs have to do with measuring oxygen concentration in the blood? Both oxygenated and de-oxygenated blood absorb light of different wavelengths, and this characteristic is used to calculate the oxygen saturation level of blood.

A brief overview of the pulse oximeter works is given below

  • Light irradiation: Both the LEDs on the oximeter project light through the skin. Due to the wavelength of the light, they penetrate the human tissue and interact with the blood flowing through the arteries.
  • Photodiode detection: The photodiode detects the light which passes through the blood and starts analysing the received photons. It also uses ambient light detection to reduce the effect of other light sources in the received signal.
  • Preprocessing: The data from the sensors is then sent to a computing device that uses the Beer-Lamberts law to calculate the R-value. This value considers the proportion of oxygenated blood to deoxygenated blood and the pulsatile component of the cardiac rhythm to calculate oxygen saturation.
  • Conversion to oxygen saturation: The R-value is then converted to Spo2 values using training data giving the Spo2 value for a particular R-value.

Due to the calculation of the pulsatile component of the cardiac rhythm, most pulse oximeters show the heart rate along with the oxygen saturation level.

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How accurate are the readings generated by Samsung smartphones?

According to a preprint research paper published in the National Library of Medicine, oximeters used on Samsung S9 and S10 devices have a root mean square deviation of 2.6 per cent for measuring oxygen saturation. According to the FDA/ISO, this deviation is in the permissible range, as it allows a maximum deviation of 3.5 percent.

Although the research shows that the RMSD value is below the FDA regulations, the paper is a preprint and has not been approved yet. Also, the tests were conducted in laboratory conditions, and a sample size of 12 volunteers was chosen for the study. In addition to this, Samsung also states that:

According to Samsung, “The accuracy of the information and data provided by these devices and related software, including heart rate readings, may be affected by factors such as environmental conditions, skin condition, specific activity performed while wearing the device, settings of the device, user configuration/user-provided information, sensor placement, and other end-user interactions ”

Also read: Top 7 apps that work with Apple Health

Nischay Khanna

A tech enthusiast, driven by curiosity. A bibliophile who loves to travel. An Engineering graduate who loves to code and write about new technologies. Can't sustain without coffee. You can contact Nischay via email:

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