CHAPTER 5 C HEMICAL S ENSORS IN O UR L IVES G. Harsanyi 1. INTRODUCTION Although materials research and development of sensor devices have been progressing rapidly, practical applications have requirements that are often mismatched to achieved results. Sensors are often applied without clear knowledge of underlying theory. There are thus debates about signal excitation mecha- nisms, signal conditioning methods, and the interpretation of both practically measurable and theoreti-