Page 874 - Basic Electrical Engineering

The advantage of creating a proportional electrical signal is that it is easy
to process and transmit electrical signals. The electrical signal obtained from
the transducer is used in the measurement system to measure, and if required

to control the quantity being measured.

12.2 CLASSIFICATION OF TRANSDUCERS

Transducers are classified on the basis of quantity to be measured or
depending upon whether external power supply is required for their operation

or not.
The classification of transducers on the basis of quantity to be measured is
shown below:

The classification of transducers on the basis of power supply requirement
are made into two categories, namely active transducers and passive

transducers.

Active transducers do not require any external source of supply for their

operation. That is why they are also called self-generating transducers.
Examples of active transducers are piezoelectric transducers,
electromagnetic-type transducers, photovoltaic-type transducers, thermo-

electric-type transducers, etc.

Passive transducers require power supply for their operation and they are

not self generating.

To understand the difference between active and passive transducers, let us
take a simple example. In Fig. 12.1 has been shown a transformer with a

movable core. The movement of the core is the measure of displacement. The
output voltage, e will depend upon the position of the core. Thus, e ∝ d,
o
o
where d is the measure of displacement. Thus, this passive transducer