The Heart Beat Sensor provides a simple way to study the heart's function.This sensor monitors the flow of blood through Finger . As the heart forcesblood through the blood vessels in the Finger , the amount of blood in the Finger changes with time. The sensor shines a light lobe (small High Bright LED ) through the ear and measures the light that is transmitted to LDR . The signal is amplified, inverted and filtered, in the Circuit .By graphing this signal, the heart rate can be determined, and some details of the pumping action of the heart can be seen on the graph
Figure 2. A sample measurement taken with the heartbeat sensor.
Figure 2 shows that the blood flowing through the Finger rises at the start of the heartbeat. This is caused by the contraction of the ventricles forcing blood into the arteries. Soon after the first peak a second, smaller peak is observed. This is caused by the shutting of the heart valve, at the end of the active phase, which raises the pressure in the arteries and the earlobe.