This sensor can be used to monitor and compare pulse rates under various exercise and rest conditions. Additionally, it can show changes of blood volume/flow in the finger or ear lobe with time. The sensor has two modes of operation: measuring the BPM (Beats per Minute) of the heart rate or displaying the analog arbitrary value of the measured signal. The electrodes are both plethysmograph-based. The sensors consist of an infrared LED transmitter and a matched infrared phototransistor receiver.