Development of Blood Pressure Monitor by Using Capacitive Pressure Sensor and Microcontroller

This paper describes the development of a Non-invasive automatic blood pressure monitor (BPM) based on a capacitive pressure sensor (CPS) with the enhanced capture, compare, pulse width modulation (PWM) module (ECCP) of the microcontroller (MCU) and Bluetooth radio communications for home health monitoring. The objective of this paper is to develop automatic blood pressure device with accuracy and low cost by using a capacitive pressure sensor and logic inverter oscillator instead of the instrumentation amplifier and bandpass filter. The biomedical real-time blood pressure (BP) signal is measured by using pressure to capacitance circuit with pulse width modulation (PWM) technology and interfaced with PIC18F4550 microcontroller. The microcontroller detects the blood pressure signal and by using enhanced module functions, with the help of proposed algorithm, the blood pressure result (systolic, diastolic, pulse) has been calculated and transmitted to the Android smartphone health application via Bluetooth communication with the presence of mini LCD display, the records are stored in the internal memory of the microcontroller. The obtained result of the proposed device was verified with standard Sphygmomanometer results.

I. Introduction

The term ”blood pressure”(BP) expresses pressure within the arteries and is equal to the side force applied by the blood on the arterial wall; it produces in the rotational the force of the contraction of the ventricles, where blood is pumped into the arteries, which can be interrupted either by constriction or expansion. Thus, blood pressure seems to be released as a result of the strength of the heart and the artery. Moreover, the blood pressure monitoring is an important indicator and sign of physiological condition of human body and known as vital signs [1].