1. High heart rate. If you moved around right before the measurement (ran up the stairs or worked out, for example) or moved around during the measurements (did squats to see how it would affect your results), measurement accuracy will be lower because your heart rate probably will jump over 90 bpm.
  2. Unstable heart rate. Similarly, if the app sees that your heart rate changes a lot throughout the measurement, accuracy will be lower. For example, say you ran up the stairs, waited for your heart rate to go down to 90, and sat down for a measurement. But your heart rate keeps dropping down to 60, which is your resting heart rate. This will also affect the results.
  3. Your finger isn’t covering the camera & flash properly. We analyze color changes in the frame, which means it’s best if your camera doesn’t pick up on any other images. This is why you need to cover the camera and flash with your finger completely. If the flash burns your finger, you don’t have to cover it all the way, but try to make sure that your finger doesn’t move and there is nothing else moving in the camera’s frame (don’t point it at the TV, for example).
  4. Small movements during the measurement. When you talk, move, or move your finger, it affects what the camera captures during the measurement. Stability is the key to getting a quality signal. If you shift your finger, this will change the color in the frame, and you’ll lose accuracy points.
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