Integrated circuit, TCTR1000, with infrared light source (950nm) and phototransistor readings

Hi. I am new to BeagleBone world. I got a school assigment using a Integrated circuit, TCTR1000, with infrared light source (950nm) and phototransistor. Basiclly we are going to messure our pulse. I got everything wired up on my breadboard and get readings, and if i multiply this with 1.800 I get volts. But how do I calculate this reading into a pulse? I am verry unsure how to go foward with this. Any helps is appreciated.

Best regards,

Nicholai Rindarøy