IntroductionThe Human Body as a Sensor SystemSensors in an AutomobileClassification of SensorsExample of a Gas Sensor: The Taguchi SensorThe Sensor as a Passive or Active ElementThe Sensor as Part of a Measurement SystemSensor PropertiesHistorical Development of SensorsSensor SystemElectrochemical SensorsConductimetric SensorsSemiconducting Metal Oxide SensorsChemiresistorsOther Solid-State Electrochemical Gas SensorsConcluding RemarksPiezoelectric SensorsClassification of Piezoelectric SensorsPiezoelectric Materials as Intelligent or Smart MaterialsThe Piezoelectric EffectThe Properties of No