Principle of electronic blood pressure monitor
We can know that if a river is originally unobstructed, but if it is forcibly plugged, then when the pressure is too great, the force of water pressure will be enough to break through these resistances to maintain the flow. The concept of blood pressure is the pressure of blood as it flows through the walls of a blood vessel. The blood that comes out of the heart needs to be pushed in order to travel around the body, and it is through the constant contraction and relaxation of the heart that the blood is pushed forward.
How is blood pressure converted to voltage?
After knowing the principle of the sphygmomanometer, we purchase a pressure sensor, the main purpose is to want to convert the physical quantity of blood pressure into a voltage signal, which works by adjusting the pressure of the gas through the pump's inflation and leakage. Because the pressure makes the pressure sensor internal material deformation, after the Huisi with the bridge after the reaction of the relative voltage difference, in turn, we can also know from its voltage changes at the time of the pressure.
What is the signal we want?
When the pressure in our wristband equals the blood pressure, the blood starts to flow and produces the so-called cuff sound, which is the systolic blood pressure, and we have to start making recordings from here until the end, when the cuff sound is gone, and this point is the diastolic blood pressure.
How do I get the systolic and diastolic signals?
When the pressure sensor is controlled by our linear inflation and deflation, there will be a DC voltage change. If we amplify the signal from the pressure sensor by a certain percentage, we can see that when the pressure is between systolic and diastolic, there will be another AC signal on the oscilloscope. At this point, we will be divided into two signals by a high-pass filter, so when the systolic and diastolic pressure occurs, the relative AC signal also occurs, then corresponds to another signal by the low-pass filter (that is, the pressure at the time), so you can know the person's systolic and diastolic pressure.