25-08-2017, 09:32 PM
PULSE RATE MONITORING
PULSE RATE MONITORING.docx (Size: 14.11 KB / Downloads: 30)
THEORY:
The pulse rate/ heart rate measurement is carried out using photoelectric sensors which uses optical signal which changes resistance of photo transistor due to change in blood volume density. The blood is ejected from the ventricles due to the heart muscles contracts; a pulse of pressure is produced and transmitted through the body circulatory system. The pressure pulse when traveling through the vessel causes vessel- wall displacement, the finger having vessel, which can be used for heart pulse measurement. This pulse is an indicator of blood pressure and flow.
Photo electric method uses transmittance type and reflection type of pulse rate measurement. .In transmittance method, light emitting diode (LED) is placed at one side of the finger and photo transistor in opposite side. Light is transmitted through the finger tip and the resistance of the photo transistor changes in the amount of light reaching it .Whenever the heart ejects the blood ventricle ,blood is forced throughout body and the amount of blood in the finger increases.It reduces the light density reaching photo transistor,whichincreases photo transistor resistance. The photo transistor connected a part of the voltage divider that produces a voltage which varies with the amount of blood in finger. This pressure pulse is converted to a digital pulse by means of a comparator which used for counting the pulses per minute.