Pulse wave travels from the heart and can be detected at the arteries, small arteries, and arterioles. To obtain he pulse wave you need to place PPG sensor to one of your hands finger, for example left hand index finger (see picture bellow).
Picture with two different pulse waves obtained at the same body location. Pulse wave at the left is from the younger subject than pulse wave at right picture. Getting older shape of the pulse changes and notch of pulse wave is declining. Therefore, first derivative can be used; closest point to zero is expressed as the peak point.
Example bellow of feature extraction from already recorded pulse wave. Pulse was recorded using HRW prototype. Pulse was obtained from the finger index of the healthy subjects aged 26 and aged 60 (video bellow).