A person's heartbeats are the sound of valves in the heart of his heart that contracts or expands by forcing blood from one region to another. The number of times the heart beats per minute (BPM) is heart rate and the heartbeat that can be felt in any artery that is near the skin is the pulse.
Two Ways to Measure a Heartbeat
• Manual mode: The heart pulse can be checked manually by checking the pulses in two positions: the wrist (the radial pulse) and the neck (carotid pulse). The procedure is to place the two fingers (index and middle finger) on the wrist (or neck below the trachea) and count the number of pulses for 30 seconds and then multiply that number by 2 to obtain the heart rate. However, the pressure should be applied minimally and also the fingers should be moved up and down until the pulse is felt.
• Use of a sensor: Heart rate can be measured based on the variation of optical power as the light is dispersed or absorbed during its course through the blood as the heart beat changes.
Principle of heartbeat sensor
The heartbeat sensor is based on the principle of photo-charting. It measures the change in blood volume through any organ of the body that causes a change in the intensity of light through that organ (a vascular region). In the case of applications in which the pulse rate is to be monitored, the momentum of the pulses is more important. The flow of blood volume is decided by the speed of the heart pulses and as light is absorbed by the blood, the signal impulses are equivalent to the pulses of the heartbeat.
There are two types of fotoflethysmography:
Transmission: Light emitted from the light emitting device is transmitted through any vascular region of the body such as the ear lobe and received by the detector.
Reflection: The light emitted from the light emitting device is reflected by the regions.