engineering notes

unit 3 Physical Variables and transducers Sensor Sensors are electrical devices that have the capability of sensing different physical variables. The sensor may be classified on different bases one of them is a physical quantity. Hence on the basis of a physical quantity or physical vibration involved the sensors are classified as: Resistive sensor The input being measured is transformed into a change in resistance. examples: potentiometer, resistance thermometer, strain gauge, etc. Inductive sensor The input being measured is transformed into a change in resistance. example LVDT. Capacitive Sensor The input being measured is transformed into a change in capacitance. example: capacitive Displacement sensor. On the basis of power supply required: Active Sensor Active sensors are those which do not require an external power supply. example: thermo-couple Passive Sensor Passive Sensors are those which require a power supply. example: Potentiometer. Physical variables and their types Th