Consisting of large-format photodiode and 3 green LEDs with wavelength of 530 nm, Model SFH 7051 monitors heart rate by measuring volume of blood passing through blood vessels. Device produces optical output of 3 x 3.4 mW at current of 20 mA and voltage of 3.2 V. Low capacitance of 11 pF ensures short switching times and high measurement frequency. With photo-sensitive area of 1.7 mm², sensor is suited for use in fitness trackers, smart watches, and other wearables.