What is an Active Transducer : Working & Its Types

The transducer is an electrical device; the main function of this is to change a physical quantity to an equivalent electrical signal. The input in most of the electrical systems is the electrical signal; however, a non-electrical signal can be changed into its equivalent electrical signal by using electrical techniques. Basically, the block diagram of a transducer includes two components namely sensing element and transduction element. The thermocouple is the best example of a transducer. It generates a voltage equivalent to the heat at the junction of two different metals. Transducers are classified into two type’s namely active transducer and passive transducer.

What is an Active Transducer?

Definition: A transducer that changes the quantity of non-electrical to electrical is known as active transducer. The best examples of nonelectrical quantities are pressure, temperature, and the illumination of light. Therefore, there are different types of active transducers based on the quantity of the non-electrical that we select. Please refer to this link to know more about the difference between an active transducer and a passive transducer.

Active Transducer
Active Transducer

This transducer doesn’t require an additional source. Its design is simple and resolution is low. The best example of this is Thermocouple, Tachogenerator, PV cell, etc.

Active Transducer Working

The best example of the active transducer is Piezo electrical crystal which is shown below. The main property of this crystal is to generate the o/p voltage once the force at the outside is applied. The arrangement of this crystal can be done in between two metallic electrodes. Once the external force is applied to the crystal, then the voltage can be induced across it. This is the working of this transducer.

Working of Transducer
Working of Transducer

Types of Active Transducer

There are three types of active transducers which include the following.

  • Piezo Electric
  • Photo Electric
  • Thermo Electric

Piezo Electric Transducer

It is one kind of active transducer and the main function of this is to generate an electrical quantity. This electrical quantity is equal to the input of the pressure. There are three substances that generate a piezoelectric effect are Quartz, Rochelle salts, and Tourmaline. The effect of piezo-electric can be exhibited through these three substances.


Photo Electric Transducer

It is one kind of active transducer and the main function of this is to generate an electrical quantity that is equal to the illumination of light input. This transducer works in two cases, when the light falls on the transducer, then it generates electrons. Similarly, this transducer generates a current because of the attraction of the electrons towards anode.

Thermo Electric Transducer

A transducer that generates an electrical quantity that is equal to the input of the temperature. The best examples of these transducers are thermistor type and thermocouple type.

Thermistor Type

The thermistor can be defined as; a resistor that depends on temperature is known as a thermal resistor and it is also known as Thermistor. Thermistor’s temperature coefficient is negative because once temperature raises then the resistance of the thermistor will be decreased. The benefit of this type of transducer is that it generates stable as well as a quick response.

Thermocouple Transducer

This kind of transducer generates an o/p voltage for an equivalent change in temperature at the input. Once the different metal wires are connected jointly in order to make two connections, then that whole arrangement can be known as Thermocouple.

How to Select a Transducer?

To select a transducer, the following factors must be considered.

  • The output impedance must be low and input impedance must be high, so that load effect can be avoided.
  • It must be accurate and errors free.
  • It should be capable to resist shocks, pressure, vibrations, etc..
  • It must have good resolution
  • The transducer must work in an acidic environment.
  • For the required signal, it must be sensitive and it must be insensitive to unnecessary signals.
    Size should be small
  • A good transducer must have a small size, low weight, and highly sensitive and less cost.


1). What are the types of transducers?

They are two types’ namely active and passive transducers.

2). What are the types of transducers based on the electrical phenomenon?

They are resistive, capacitive, inductive, photoelectric and photovoltaic

3). What are the requirements of a good transducer?

They are small size, less weight, low cost, and high sensitivity.

4). What is the main difference between active and passive transducer?

The active transducer generates output without using external power source whereas passive transducer uses an external power source.

5). What is a passive transducer?

A transducer that converts the energy from non-electrical to electrical using an external power source is known as a passive transducer.

6). Is RTD an active device or passive device?

RTD is a passive device.

7). Which device is known as a self-generating transducer?

The active transducer is known as self-generating transducer because they develop their self current or voltage.

Thus, this is all about an overview of the active transducer. Transducer plays a key role in different fields like control engineering, instrumentation field. The main function of this is to convert the energy from nonelectrical to electrical. Here is a question for you, what is a passive transducer?