The word “sensor” comes from the root “sens” which means “to feel” and “to perceive”. A sensor can convert physical quantities such as                             temperature, pressure and humidity into digital or analog electrical quantities. Sensors are one of the most functional instruments in industrial            automation. They act the same way five senses act in human being. In order to achieve the ideal speed and precision in industrial processes (such          as in production lines), the available instruments and machines in production line need to be working automatically and with desired order and              precision. Therefore, in order to achieve the required effects, sensors are positioned in various places. The function of sensors and their ability to         connect to various devices such as PLC, has made them an inseparable part of the automatic control devices.
 
       Sensors are divided into two categories; Contact Sensor (Micro-switch) and NONContact Sensor (Proximity Sensor), which in turn are divided             into several subcategories.
 
        Contact Sensors
        They are used for measuring the temperature of the environment. These sensors measure their own temperature and after contacting another             object or situating in the environment, thermal balance between sensor and the environment is reached and measured.
 
       Proximity Sensors
      This type of sensors activates after a device or an object comes close to their vicinity.
 
 
      Some of the most functional sensors in industry include Fiber Optic sensors, Capacitive Sensors, Inductive Sensors.