According to William D.C, transducers are divided into 2 classifications based on the energy source they need, namely:
a. Self generating transducer (self generating transducer)
Self-generating transducers are transducers that require only one energy source. Example: piezo electric, thermocouple, photovoltaic, thermistor, etc.
The characteristic of this transducer is that it generates an electrical energy from the transducer directly. In this case the transducer acts as a voltage source.
b. External power transducer
External power transducer is a transducer that requires a certain amount of energy from the outside to produce an output.
Examples: RTD (resistance thermal detector), Starin gauge, LVDT (linear variable differential transformer), Potentiometer, NTC, etc.