The Pixel 8 Pro thermometer can measure body temperature with a small tweak

The Pixel 8 Pro has been out for a little over a week now, and the tinkerers are already digging into the device’s temperature sensor. One of the biggest omissions with the temperature sensor is its inability to measure human body temperature, with Google saying it’s working with the U.S. Food and Drug Administration (FDA) to make it happen.

The thing is, the Pixel 8 Pro can measure human body temperature, it just needs a little help to make it happen — and, apparently, some leniency for when (not if) the phone gets it wrong.

But to understand how the Pixel 8 Pro could measure body temperatures, it’s important to understand how it measures temperatures in the first place.

Kamila Wojciechowska, the person behind several major Google Pixel leaks over the last few years, took to X (Twitter) to share several details about the Pixel 8 Pro’s temperature sensor. Wojciechowska explains that the Pixel 8 Pro uses an infrared thermometer to measure temperature. These types of temperature sensors measure infrared (also called thermal) radiation emitted by moving molecules in an object. As objects heat up, molecules move more, emitting more infrared.

Not all surfaces emit this radiation the same, though – some of them do it more effectively than others. Knowing this characteristic (known as “emissivity”) is crucial to estimating the temperature of an object.

This is why the thermometer app asks you to select the material. pic.twitter.com/pEeGJ4ivvk

— kamila 🌸 (@Za_Raczke) October 21, 2023

However, different surfaces have different levels of ’emissivity,’ or how effectively said surface emits thermal radiation. Therefore, knowing the emissivity of a surface is crucial to accurately measuring the temperature of an object (and thus, the Pixel 8 Pro’s thermometer app asks people to select the material of the surface they want to measure).

The Pixel 8 Pro is measuring skin temperature, not core body temperature

Okay, now that you know how the Pixel 8 Pro measures temperatures, we can look at measuring body temperatures. First, the ‘Food & organic’ material option in the thermometer app would be the best choice for measuring body temperature since humans are made of organic material after all. But if you pick this option and measure your temperature, you’ll notice the result is too low. For example, in a quick test I did, I got 32.8°Celsius (or 91.04°Fahrenheit for any Americans reading this).

Well, Wojciechowska explained that “most thermometers lie,” noting that skin temperature — which is what the Pixel 8 Pro is measuring — is usually lower than the core body temperature, which is 36.5–37.5°C (97.7–99.5°F). Wojciechowska went on to quote an article about body temperatures in The Journal of Nutrition, which states the surface temperature of the body is “4° or 5° lower than the interior temperature.”

In other words, my example measurement of 32.8°C is accurate, but only if you add 4°C to it.

Well, most thermometers lie. When we think of body temperature we usually think of the core temperature, which is typically ~36.6c. This, however, is much higher than skin temperature.

According to Alan C. Burton’s article (https://t.co/lWCROWjhrU), it’s usually 4-5c colder. pic.twitter.com/fOtVPNmdmu

— kamila 🌸 (@Za_Raczke) October 21, 2023

With that in mind, it should be relatively simple for Google to implement body temperature measurements by adjusting the thermometer app to calculate for the difference between the body’s surface and core temperatures. The calculation would be more complex than simply adding 4°C to every temperature measurement taken from a person, since people are quite different and core body temperatures and surface temperatures can fluctuate. However, with the right calculations, it can be pretty accurate — Wojciechowska pointed to a formula someone shared on GitHub that achieved an error rate of about “+- .3°C.”

Wojciechowska also suggests Google could further enhance the accuracy by pulling in Fitbit data or by taking multiple measurements. Moreover, it would be easy to automate that with an app, but Wojciechowska highlights another thread from Android expert Mishaal Rahman noting that Google locked down the temperature sensor so only preinstalled or Google-signed apps can access it.

So the Pixel 8 Pro can measure body temperature, but is it accurate?

So with all that said, Pixel 8 Pro owners can measure their body temperature by just scanning their skin with the ‘Food & organic’ option and adding about 4°C to the result, at least until the FDA (or Health Canada for us) approves it.

But while the Pixel 8 Pro can measure body temperature, it doesn’t mean it should.

Both Android Police and Android Authority have done a bunch of testing with the Pixel 8 Pro’s thermometer and concluded it wasn’t particularly accurate. In Android Authority’s testing against an industrial infrared thermometer, the Pixel 8 Pro’s reading was often off by as much as 5°C.

In other words, the Pixel 8 Pro temperature sensor really isn’t reliable enough to use for accurate temperature readings, body temperature or otherwise.

Source: Wojciechowska, Rahman Via: Android Police, Android Authority