Blood Pressure Sensor (1)

Abstract

Blood pressure is a simple and important index to determine a people healthy or not. An abnormal blood pressure is a factor cause stroke and coronary heart disease. Unfortunately, there is no symptom for abnormal blood pressure. For example, hypertension is very common in citizen. However most of the people with hypertension do not recognize it since they have not measure their blood pressure constantly. Although there are blood pressure monitor in the market, it is not popularize since there are some disadvantages on them. It is not convenience, expensive, cuff require and large size. In order to facilitate citizen to evaluate their personal health, a blood pressure sensor, which can solve the above disadvantages, is necessary to develop. In order to measure the blood pressure, photoplethysmography (PPG) technology was used. Two sets of infrared optical sensors were required. Light would be emitted into the skin while the reflected light would be detected. Heart rate from the skin would be obtained by detecting the light transmitted through the skin. The sensors were put on the finger and upper arm separately. By calculating the time difference between the two heart rate pulses, the pulse transmit time (PTT) was obtained. There is a linear relationship between the pulse transmit time (PTT) and blood pressure. By making good use of the relationship, blood pressure of the user was obtained. Moreover, heart rate can also be obtained by PTT. This report would include the working principle of the sensors, data computing and programming display.