Data Acquisition System for Clinical Research in Plethysmographic Signal

Abstract

Photoplethysmography (PPG) is a non-invasive optical technique used to monitor blood volume changes in peripheral tissues. This paper presents the design and implementation of a low-cost, modular data acquisition (DAQ) system for capturing PPG signals using the MLT1020 sensor. The system includes a custom analogue front end with a bandpass filter (0.5–5 Hz), combining a 5th-order high-pass and 7th-order low-pass filter to suppress noise and motion artefacts. The output signal is visualised in real-time on a Digital Storage Oscilloscope (DSO) and later analysed in MATLAB. Experimental results from human subjects showed clean, periodic waveforms with reliable cardiac cycle representation. Signal quality was comparable to that obtained from commercial DAQ systems, confirming the system’s effectiveness for basic biomedical research. The setup is particularly suited for educational and research settings where cost and customisation are key. Future versions may include microcontroller integration, wireless communication, and digital storage. This system bridges the gap between theory and hands-on experimentation, providing an accessible platform for physiological signal processing.