Galaxy S5 uses a built-in heart rate sensor to monitor your heart rate constantly and with more accuracy. To use Heart Rate Sensor on Galaxy S5 and measure your heart rate, do as follows:
1. Go to App drawer, and open S Health app
2. Tap the Heart Rate icon on the bottom of the screen*
3. Now, all you have to do is put your finger on the Heart Rate Sensor located below the camera
4. Wait for the process to complete and see how fast your heart is beating
*By default the Heart Rate icon should be on the quick buttons on the bottom of the screens, but if for some reasons you can find the Heart Rate button, swipe the screen from the left edge to the right and select "Heart Rate" from the opened sidebar.
1. Put your finger on the sensor gently, and don't press at all
2. Keep both your finger and the phone still