Sensors are used to measure physical, chemical and biological quantities. The book offers a comprehensive overview of physical principles, functions and applications of sensors. It is structured according to the fields of activity of sensors and shows their application by means of typical examples. Measured variables that can be recorded by sensors are e.g. mechanical, dynamic, thermal, electrical and magnetic. Furthermore, optical and acoustical sensors are discussed in detail in the book. The sensor signals are recorded, processed and converted into control signals for actuators. Such sensor systems are also presented.