On the back of the new Apple Watch, there are two sets of lights and sensors. One sends out and receives visible light, while the other works in the infrared part of the spectrum. Together, they form the technical core of the watch\u2019s coolest feature\u2013a heart rate monitor.<\/p>\n
This kind of design\u2013using optical sensors to measure pulse\u2013is not unprecedented, but Apple, of course, claims to have improved the system over competitors like the Basis Peak, Samsung Gear Fit, or Mio\u2019s line of activity monitors. Which would be a good thing, because these systems have struggled with their accuracy.<\/p>\n
And because of the technology that most smart watch makers, including Apple, have chosen, the problems may be exacerbated if you have darker skin.<\/p>\n
The technology is based on a laboratory technique called photoplethysmography, which uses a \u201cpulse oximeter\u201d to measure the components of the blood. A light pulse is sent through the skin and picked up by a sensor. Based on how the light scatters, the sensor can measure how oxygenated the blood is, which allows one to calculate heart-rate based on how often fresh, arterial blood is pumping through.<\/p>\n
In the medical context, this oxygen level tends to be measured by a little finger cuff. So the light is on one side of the finger and the sensor is on the other. Even in this more controlled setting, there have been conflicting scientific reports about whether skin color impacts the accuracy of readings.<\/p>\n
But no one wants to wear a finger cuff around while they work out, so fitness band companies have had to make do with the wrist. Even a flashlight can shine easily through one\u2019s fingers, which makes the sensing task easier. A wrist-mounted sensor has to rely on the light that\u2019s reflected back from the blood, not shining through it. That\u2019s harder.<\/p>\n
The skin on the back of the wrist tends to be darker, too, especially for people with more melanin. \u201cThe light has to penetrate through several layers\u2026and so the higher the person is on the Fitzpatrick scale (a measure of skin tone), the more difficult it is for light to bounce back,\u201d explained Basis COO Bharat Vasan to CNET.<\/p>\n
Basis, and presumably Apple, try to compensate for skin tone by shining brighter light when someone\u2019s complexion is darker.<\/p>\n
Using optical technology to measure heart rate might also mean that people with darker skin will experience a greater drain on their watch battery, because of the more intense light required to power the sensor. The light required to do accurate measurements was enough to push Apple-competitor Jawbone away from an optical system to an electrical one: \u201cBecause bioimpedance requires significantly less power compared to optical sensors for same level of accuracy, we can deliver a smaller form factor and longer battery life,\u201d they claim.<\/p>\n
Source: Fusion<\/p>\n","protected":false},"excerpt":{"rendered":"
On the back of the new Apple Watch, there are two sets of lights and sensors. One sends out and receives visible light, while the other works in the infrared part of the spectrum. Together, they form the technical core of the watch\u2019s coolest feature\u2013a heart rate monitor. This kind of design\u2013using optical sensors to … Continue reading “Is Apple’s latest feature for Whites only?”<\/span><\/a><\/p>\n","protected":false},"author":2961,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,123],"tags":[1203,156,11185,11183,157,11184,11186],"class_list":["post-18007","post","type-post","status-publish","format-standard","hentry","category-news","category-world","tag-apple","tag-blacks","tag-dark-skin","tag-heart-rate-monitor","tag-racism","tag-skin-colour","tag-skin-tone"],"cc_featured_image_caption":{"caption_text":false,"source_text":false,"source_url":false},"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/posts\/18007","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/users\/2961"}],"replies":[{"embeddable":true,"href":"https:\/\/praag.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=18007"}],"version-history":[{"count":1,"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/posts\/18007\/revisions"}],"predecessor-version":[{"id":18008,"href":"https:\/\/praag.org\/index.php?rest_route=\/wp\/v2\/posts\/18007\/revisions\/18008"}],"wp:attachment":[{"href":"https:\/\/praag.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18007"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/praag.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18007"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/praag.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18007"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}