The characteristics of the sensor include: miniaturization, digitalization, intelligence, multifunctionality, systematization and networking. It is the primary link to realize automatic detection and automatic control. The existence and development of sensors allow objects to have senses such as touch, taste and smell, so that objects slowly become alive. Usually according to its basic sensing function is divided into heat-sensitive components, light-sensitive components, gas-sensitive components, force-sensitive components, magnetic components, moisture-sensitive components, acoustic components, radiation-sensitive components, color-sensitive components and taste-sensitive components, such as the ten major categories