Active vs Passive Transducer: Difference and Comparison

Key Takeaways

1. Active Transducers require an external power source, whereas Passive Transducers generate their output without one.
2. Active Transducers provide an output in the form of voltage or current, while Passive Transducers produce a change in resistance, capacitance, or inductance.
3. Active Transducers have a better signal-to-noise ratio than Passive Transducers.

What is Active Transducer?

Active transducers require an external power source to convert one type of energy into another and can employ in various applications, including sound systems and medical imaging. Electrical signals convert into mechanical movement, heat, light, or sound.

Active transducers use an electrical signal to cause a physical change, such as a change in pressure, temperature, or frequency. The signal is either amplified or reduced before being applied to the transducer.

Standard active transducers include electromechanical transducers, thermistors, and piezoelectric transducers.

Thermistors are temperature-sensitive transducers that convert electrical signals into temperature changes. They are used in temperature control systems like thermostats. Piezoelectric transducers transform the transmission of electrical such as ultrasound into mechanical vibrations. These transducers are frequently used in medical imaging because they can generate sound waves to create an image of an internal organ.

Electrical signals convert into mechanical movements via electromechanical transducers, such as turning a motor or opening a valve. These transducers are deployed in sound systems to convert electrical signals into sound waves.

Active transducers are incredibly adaptable and utilized in various applications. They are also quite simple to operate and maintain, making them an excellent choice for many applications.

What is a Passive Transducer?

A passive transducer is a device that converts energy from one form to another without the use of an external source of power. It is a gimmick that can measure physical quantities such as temperature, pressure, force, and displacement without requiring an external power source. 

Passive transducers measure the physical qualities of a system or environment. Strain gauges are the most frequent sort of passive transducer. A strain gauge is a device that measures the strain (deformation) of an object or material. It includes a short strip of metal or other material affixed to the object or material to be measured.

As the thing or material is subjected to a force, the strip deforms and changes resistance, which can then be measured. Other types of passive transducers include:

• Thermistors measure the temperature of a system or environment.
• Piezoelectric transducers measure force or pressure.
• Optical sensors measure light intensity.  

Passive transducers operate in industrial applications, such as estimating the pressure of a gas or liquid or a system’s temperature, and are used in medical applications, such as counting the heart’s electrical activity. They can gauge the force delivered to a structure, such as a bridge, or the displacement of an object.

Passive transducers are uncomplicated and steadfast devices that do not require an external power supply to process. Nonetheless, the variety of physical qualities they can measure is limited, and their exactitude is lower than that of active transducers.

Difference Between Active and Passive Transducer

1. Active transducers require an external power source, whereas passive transducers do not.
2. Active transducers convert energy into electrical form, whereas passive transducers convert energy into mechanical form.
3. Active transducers do not need an amplifier to increase their signal level, whereas passive transducers require an amplifier to increase their signal level.
4. Active transducers generate their energy source, but passive transducers rely on external energy sources.
5. Active transducers are more intricate and more pricey than passive transducers.

Comparison Between Active and Passive Transducer

Parameters of Comparison	Active Transducer	Passive Transducer
Also known as	Self-generating transducers.	Externally energized transducers.
Conversion	Simple	Complex
Generated output	Electrical current or voltage.	Variation in quantity associated with passive elements
Operational energy	It is derived from the quantity being measured.	Taken from an external power source.
External energy	Not required	Required

References

1. Pressure measurements in the microcirculation with active and passive transducers – ScienceDirect
2. Transducers | SpringerLink

Last Updated : 29 July, 2023