Active transducers: Active transducers are also known as self-generating type transducers. They do not require external power source to produce the output. They work under energy conversion principle. Active transducers develop their own voltage or current. The energy required for the production of the output signal is obtained from the physical phenomenon being measured.
Ex: piezoelectric transducer, thermocouple
Passive transducers: Passive transducers are also known as externally powered transducers. They require external power source to produce the output. They work under energy controlling principle. Ex: resistive, capacitive, inductive transducer.