Difference Between Active Transducer and Passive Transducer

Transducers are elements that can transfer energy from one form to another, and most of them are employed in translating physical variables like temperature, pressure, or force into electrical signals. There are two primary types of transducers: mechanical, electromechanical, and acoustic transducers. Even though both gadgets perform a similar task, one requires an external source of power to operate, while the other one is self-powered. In this article, the differences between active and passive transducers, how they operate, what benefits one is over the other, and vice versa will be expounded to aid in the determination of the most suitable type for a specific use. 

What is an Active Transducer?

An active transducer does not utilize any external power to produce output or take input in a system. These transducers produce electricity directly from physical quantities like heat, light, pressure, etc. Hence they are known as conversion transducers. 

Advantages of Active Transducers

• No external power is required. The active transducers work separately; that is why their construction is easier. 
• Self-generating: These transducers have the capability of directly converting the measured quantity into an electrical form. 
• Low cost: Compared to passive transducers, it is relatively easier to construct and therefore most often cheaper as well. 

Disadvantages of Active Transducers

• Low resolution: Due to their ability to produce an output signal that is proportional to a measured parameter Active transducers have lower resolution as compared to passive transducers. 
• Limited accuracy: It is also essential to remark that the accuracy of active transducers is less as compared to passive types. 

Example:

Thermocouples are one example of active transducers, as among the passive transducers there are resistive, capacitive, inductive, and other types. These devices produce a voltage in a manner that is directly proportional to the temperature difference of two junctions. 

What is a Passive Transducer?

Passive transducers are electrical devices that receive a signal and then donate an equivalent level of signal in response to the stimulus received. 

In contrast to an active transducer, a passive one has no power source of its own and needs to take power from some other source. It does not produce an electrical signal independently but rather augments the exterior power to transform physical quantities into an electrical signal. The output here depends on changes in electrical properties such as resistance or capacitance by the measured quantity. 

 Advantages of Passive Transducers

• High resolution: Another difference is that passive transducers are capable of yielding a higher accuracy due to their ability to detect small changes in physical quantities. 
• Precise measurements: These transducers can ideally measure small changes in output, and therefore, they’re used where accuracy is needed. 

Disadvantages of Passive Transducers

• External power required: Because passive transducers require the supply of external power, their design becomes complicated. 
• More complex: Because they require extra circuitry and power control in their function, passive transducers are usually more complex in design than active transducers. 

Example:

Passive transducers are those transducers that do not require any external power to work, such as strain gauges, capacitive transducers, thermistors, etc. These devices change their resistance, capacitance, or inductance depending on the physical stimulus that is exerted on them. 

Difference Between Active Transducer and Passive Transducer

Conclusion 

All in all, the active and passive transducers are of immense importance in the process of transforming the physical signals to electrical output. Active transducers only require an excitation source to supply electrical power in order to operate; hence, they are simpler and cheaper to construct than passive transducers, but they do not offer the level of accuracy that is available with passive transducers, which require external power. The active transducer is preferred over the passive one if the sensitivity and the complexity of the application demanded are high.