The probe (the clip) emits beams of red and infrared light through your highly vascularized fingertip or earlobe.Light Absorption: The sensors on the other side of the clip measure exactly how much light passes through the tissue.Pulse Detection: It isolates arterial blood flow by detecting the rhythmic pulse, ensuring it only measures blood moving during a heartbeat.The Calculation: An internal microprocessor calculates the ratio of absorbed red light to infrared light.