A sensible distinction is to use 'sensor' for the sensing element itself
and 'transducer' for the sensing element plus any associated circuitry.
All transducers would thus contain a sensor and most (though not all) sensors
would also be transducers.
Figure 1 shows the sensing process in terms of energy conversion. The
form of the output signal will often be a voltage analogous to the input
signal, though sometimes it may be a wave form whose frequency is proportional
to the input or a pulse train containing the information in some other