Evaluation And Applications Of Gas Sensors

Gas sensors are used widely for environmental and biomedical uses. This work focuses on verifying specifications of commercial-off-the-shelf (COTS) gas sensors and their particular applications. The first chapter in this thesis gives a literature review on gas sensors, especially metal-oxide based sensors and their advantages. The second chapter focuses on evaluation of COTS NO2 sensors. The purpose is to establish a characterization method to evaluate gas sensors. I have evaluated three COTS metal-oxide based NO2 sensors and a COTS electrochemical sensor for comparison. Four different tests have been implemented to investigate the sensitivity, humidity effects, temperature effects, and selectivity for each sensor. A general method for calibration and uses of metal-oxide based NO2 sensor for environmental monitoring is discussed.

Chapter 3 focuses on a specific metal-oxide based CO2 sensor and its application to fight the Sudden Infant Death Syndrome (SIDS) problem. In this chapter, I discuss SIDS and the importance to prevent it. A COTS CO2 sensor has been characterized for designing the system. A complete system using the radio frequency identification (RFID) technique to monitor multiple infants has been proposed and designed. A system that can be used to monitor two infants simultaneously has been designed and assembled with printed circuit boards (PCBs). The overall system has been characterized under practical considerations. The results are as predicted. Chapter 4 discusses a web-based search engine system from which users can search for specific sensors with desired specifications. An Active Server Page (ASP) using VBscript and Microsoft Access Database is used to implement the system. The database of sensors is stored in the server. Chapter 5 concludes the thesis with discussions of future works and the trend of utilizing gas sensors to improve human life.