Classification of Electrical Transducers

Classification of Electrical Transducers

Transducers may be classified according to their structure, method of energy conversion and application. Thus we can say that transducers are classified

•           As active and passive transducer

•           According to transduction principle

•           As analog and digital transducer

•           As primary and secondary transducer

•           As transducer and inverse transducer

Active and Passive Transducer

Active Transducers

Ø     Active transducers are self-generating type of transducers.

Ø     These transducers develop an electrical parameter (i.e. voltage or current) which is proportional to the quantity under measurement.

Ø     These transducers do not require any external source or power for their operation.

Ø   They can be subdivided into the following commonly used types

Passive Transducers

Ø     Passive transducers do not generate any electrical signal by themselves.

Ø  To obtain an electrical signal from such transducers, an external source of power is essential.

Ø     Passive transducers depend upon the change in an electrical parameter (R, L, or C).

Ø     They are also known as externally power driven transducers.

Ø     They can be subdivided into the following commonly used types.

According to Transduction Principle

The transducers can be classified according to principle used in transduction.

•           Capacitive transduction

•           Electromagnetic transduction

•           Inductive transduction

•           Piezoelectric transduction

•           Photovoltaic transduction

•           Photoconductive transduction

Analog and Digital Transducers

The transducers can be classified on the basis of the output which may be a continuous function of time or the output may be in discrete steps.

Analog Transducers

Ø These transducers convert the input quantity into an analog output which is a continuous function of time.

Ø A strain gauge, LVDT, thermocouples or thermistors are called analog transducers as they produce an outp which is a continuous function of time.

Digital Transducers

Ø Digital transducers produce an electrical output in the form of pulses which forms an unique code.

Ø   Unique code is generated for each discrete value sensed.

Primary or Secondary

Ø     Some transducers consist of mechanical device along with the electrical device.

Ø     In such transducers mechanical device acts as a primary transducer and converts physical quantity into mechanical signal.

Ø     The electrical device then converts mechanical signal produced by primary transducer into an electrical signal.

Ø     Therefore, electrical device acts as a secondary transducer.

Ø     For an example, in pressure measurement Bourdons tube acts as a primary transducer which converts a pressure into displacement and LVDT acts as a secondary transducer which converts this displacement into an equivalent electrical signal.

Transducer and Inverse Transducer

Ø     Transducers convert non-electrical quantity into electrical quantity whereas inverse transducer converts electrical quantity into non-electrical quantity.

Ø     For example, microphone is a transducer which converts sound signal into an electrical signal whereas loudspeaker is an inverse transducer which converts electrical signal into sound signal.