Development of a low-cost, compact, wireless, 16 - channel biopotential data acquisition, signal conditioning and arbitrary waveform stimulator system

Abstract

Biopotential signals or biosignals, including ECG, EMG, EEG, and EOG, play an important role in assessing human health, aiding in disease diagnosis, and monitoring physiological conditions. However, most commercially available biopotential data acquisition (Bio DAQ) systems are wired and designed for specific signals, resulting in limitations such as discomfort during extended use and incompatibility with animal studies. Wireless Bio DAQ systems represent a significant technological advancement, offering improved flexibility and enhanced user comfort. While various Bio DAQ systems are available in the market, most are optimized for individual signal types like EMG, ECG, or EEG, with predefined amplifier gains and filter frequencies, making them unsuitable for capturing multiple biosignals simultaneously. Additionally, wired systems are impractical for animal studies. Several design approaches have been explored for developing wireless Bio DAQ devices. In this study, we present a compact, 16-channel wireless biopotential data acquisition (Bio DAQ) system integrated with an electrical stimulator. Our proposed design incorporates multiple innovative and flexible features: (1) Each channel includes user-selectable digital filters, optimized for specific signal frequencies such as EMG, ECG, EEG, and EOG, enabling simultaneous multi- signal acquisition. (2) The system features variable gain functionality combined with an upgradable analog bandpass filter. (3) It supports multi-subject monitoring by acquiring biosignals from up to four patients simultaneously. (4) Both two-electrode and three-electrode configurations are supported for signal acquisition. (5) The integrated stimulator generates a biphasic, charge-balanced, trapezoidal, stimulus output with a near-zero DC offset, along with user-configurable pulse duration and stimulus frequency options. The developed system underwent extensive testing using both simulators and real-life biopotential signal acquisitions. Additionally, it was subjected to rigorous safety evaluations, including electrical safety testing and electromagnetic interference (EMI) testing, in accordance with international standards, ensuring compliance with medical device safety regulations. The proposed system marks a substantial improvement over existing technologies by combining reconfigurable hardware with cutting-edge signal processing methods. The thesis is structured into five chapters. Chapter 1 serves as an introduction, provides an overview of biopotential signals (ECG, EOG, EEG, EMG) and the limitations of existing Bio DAQ systems. It outlines the specific objectives of this research. Chapter 2 provides an extensive literature review on wireless Bio DAQ system with future scope for development. In Chapter 3, we have discussed the development of the circuit for various sub systems like Analog Front End (AFE), Wireless Module, Microcontroller Unit (MCU), Stimulator Module, Power Supply, and Display Unit. Chapter 4 details the development of a fully functional prototype by integrating key subsystems. The process begins with circuit implementation on a breadboard, followed by iterative testing, and culminates in a compact, single PCB module. The chapter also covers the testing and results to validate the prototype’s effectiveness, demonstrating its capability to acquire high-quality biopotential signals and meet its intended objectives. Chapter 5 discussed the conclusions and future perspectives of this work.