Basically,transducer is a electronic device that converts energy from one form to another.An electrical transducer is a device which is capable of converting the physical quantity into a proportional electrical quantity such as voltage or electric current.Transducer can be classified into many ways on various basis like : power supply,applications, output signal etc.
Different sensors can be used in different applications. Various Sensors can be used for the measurement of various parameters. eg- Potentiometer can be used for the measurement of displacement, Strain gauge can be used for the measurement of mechanical quantities like a strain . Similarly,Piezoelectric sensors can be used to measure changes in pressure,acceleration,temperature,strain or force by converting them to an electrical charge and Resistive hygrometer ,Capacitive hygrometer, Aluminum hygrometer etc a