Question
i study in electronic and electrical engineering and i have project now
adays about how the blood pressure electronic circuit works ( i.e i am
looking for electronic circuit of blood pressure monitor to be studied and
constructed ),finally i am sorry if my Q is not clear yet and thank u
again for your help. see u in good health.
omar from libya
Answer
Omar,
The simplest blood pressure device you can construct a simple device called a plethysmograph. It shines light through a fingertip or an ear lobe. As the blood pressure changes the blood corpuscles change density and absorb a different amount of light. The output can be displayed on an ordinary oscilloscope and it clearly will show the diastolic and systolic pressure peaks. It will not give you absolute blood pressure.
The circuit can be very simple and I built one as a student. The circuit and the project description was in Popular Electronics or Popular Science Magazine in the 1960's or early 70's.
How much hobby work have you done with operational amplifiers? (op amps) I would have to search through my files to find the exact circuit.
The circuit uses a phototransistor and an LED. The LED is on one side of your finger and the phototransistor on the other. An op amp biases the phototransistor so that it is in the linear region and adjusts to changes in ambient light. The output of the phototransistor is connected to a second op amp through a capacitor (AC coupled). The output of the second op amp will show a waveform that is exactly the frequency of your heart beat. The peaks and valleys correspond to diastolic and systolic blood pressure.
Good Luck!
http://www.epemag.wimborne.co.uk/
http://ourworld.compuserve.com/homepages/Bill_Bowden/homepage.htm
http://www.electronic-circuits-diagrams.com/
http://www.uoguelph.ca/~antoon/circ/circuits.htm
http://vrd.askvrd.org/services/answerschema.xml
