Sensors and encoders

A sensor or ‘feeler’ is an artificial execution of what is called a sense in biology. Most sensors are fitted electrically or mechanically. Software sensors and ‘virtual’ sensors are also possible. With a sensor, a machine perceives the surrounding or information can be collected with which processes can be operated in industry and informatics. A sensor measures a physical quantity. The quantities are, among others, in the following domains: radiation, pressure, temperature, magnetism, chemistry.  Sensors convert the quantity measured into a standardized 0/4-20 mA or 0/4-10 V control signal for further modification, for instance through an analog-digital converter to a programmable logic controller (PLC) or distributed control system (DCS). Sensors can be made based on the same technology as microprocessors and memories in PCs (chip technology), as well as with other technologies.

Source: Wikipedia