LED Heart-Rate Monitoring
The 80’s brought us many memorable things from Atari’s to Sony Walkman’s. One of our favorites though was from Polar Electro, or Polar, which was the first wireless EKG heart rate monitor developed for the Finnish National Cross-Country Ski Team. Although very cool (no pun intended) and still a benchmark for accuracy not everyone wants to wear a strap around their chest, giving rise to the use of optics and LED heart-rate monitoring technology used in watch and fitness monitors today. We’ve included a video below of Colin from Colin’s Lab to explain the theory of using LED’s to monitor heart-rate.
One of the topics that often comes up is the use of green or red LED’s when engineering a solution to measure heartrate.  Our friends at Apple use green LED lights for accuracy in a method called photoplethysmography (or PPG). Because blood absorbs green light, and each pulse brings a spike in blood flow, determining heart rate is a matter of measuring the changes in green light absorption. However, this takes up a lot of battery power so during non-work out events they use red LED’s. Just as blood absorbs green light, it also reflects red light, so they monitor activity on a minute basis using red LED’s before deploying the green LED’s for accuracy during a workout event. To determine what’s right for you, contact us and let’s engineer it!