Overview: This article explores the advancements in transducer technology, covering energy conversion types, applications in various industries, and ongoing research to improve their efficiency and performance in modern systems.

Having got ourselves in the digital domain, we regularly engage with sensors and transducers via smartphones, wearables, cars, cities, homes, and offices. After decades of research and development, sensor-and-transducer-based systems have seen significant advancements, making daily life more comfortable. Transducer-integrated systems applications like robots, autonomous driving, and smart homes are already improving people's quality of life by making them safer, more comfortable, and easier.

What is a transducer?

A transducer is a device that converts one form of energy into another, and typically, it is a device that transforms a physical quantity, such as sound, pressure, or temperature, into an electrical signal or vice versa. For instance, a microphone is a transducer that transforms sound waves into electrical impulses. On the other hand, a speaker is another type of transducer that transforms electrical signals into sound waves. One such example is pressure transducer PX429-030GV by OMEGA Engineering, as shown in Fig. 1. 

Fig. 1 High accuracy pressure transducer PX429-030GV by OMEGA Engineering Source: oemsecrets

Key Components of Transducer

As shown in Fig. 2, a transducer consists of two main components: sensing and transduction elements.

Fig. 2 Key components of transducer Source: Rakesh kumar

Sensing Element: It senses the quantity to be measured and gives it to the transduction element.

Transduction Element: This part converts the input energy from the sensing element into a different form, usually an electrical signal that can be easily processed and analyzed.

Types of Transducer

Transducers are vital in various fields, including measurement, control systems, and data acquisition. There are several types of transducers based on different criteria, as shown in Fig. 3, which include:

Fig. 3 Types of transducer Source: Rakesh Kumar, Ph.D.

Based on the Power Source

Active transducers: They do not require an external power source to operate. Examples include thermocouples and piezoelectric sensors.

Passive transducers: They require an external power source to operate. Examples include strain gauges and photocells.

Based on Energy Conversion

Mechanical transducers: They are a set of primary sensing elements that respond to changes in a physical quantity with a mechanical output. Simply put, they convert physical quantities into mechanical outputs or vice versa.

Electrical transducer: They are sensing devices that transform a physical, mechanical, or optical quantity into an electrical voltage/current proportional to the input measurement. In other words, they convert non-electrical energy into electrical energy. Mostly, the quantities to be measured are non-electrical, such as temperature, pressure, etc., which cannot be measured directly. They are sensed and changed into electrical form for easy measurement. 

Based on the Transduction Principle

Capacitive transducers: These devices change capacitance based on changes in physical quantity.

Inductive transducer: Work on the principle of inductance change. Used in measuring pressure, vibration, position, displacement, etc.

Photoelectric transducer: They use light to measure physical quantity such as temperature, pressure, or displacement by converting light energy into electrical signals or vice versa.

Piezoelectric transducer: Convert mechanical stress into electrical signals based on the piezoelectric effect.

Thermoelectric transducer: It is a device that converts temperature differences into electrical energy or vice versa, based on the thermoelectric effect or seeback effect.

Magnetic transducer: These transducers use the magnetic effect to convert a magnetic field into an electrical signal.

Based on the Output Signal Type

Analog transducer: Converts continuous physical quantities into continuous electrical signals.

Digital transducer: Convert discrete physical, quantized output signals into discrete electrical signals in binary format.

The piezoelectric transducer is briefly described in this article.

Piezoelectric Transducer

Converting electrical energy into mechanical energy, or vice versa, is the basic principle of the operation of piezoelectric transducers. The piezoelectric transducer can be considered a two-port network. The transducer receives an alternating electric signal at its input port, and mechanical vibration is generated at the transducer's output port using the piezoelectric effect. 

They are widely utilized as emitters, sensors, resonators, filters, and actuators in a variety of applications, including ultrasonic cleaning, welding, and piezoelectric motors and transformers. Piezoelectric transducers are resonant devices, and the energy conversion efficiency and the mechanical output are at their highest when running at the resonance frequency. 

Factors Affecting the Performance of Piezo Electric Transducer

The geometrical, material, and loading conditions of the transducer are the primary factors that influence their efficiency. Numerous geometries and configurations are available, ranging from micro- to macro-scale cylinders, arrays of transducers, and rectangular or circular plates, depending on the application, needs, and material qualities. Even though every effort has been made to use the best material and geometry for each application, researchers always look for ways to improve performance. 

Some of these methods include:

  • Increasing the acoustic field generated for actuation and/or transmission
  • Improving the transducer's sensitivity for sensor and/or receiver applications

To accomplish this, research has been made to improve efficiency by varying the shape and geometry of the transducer, as well as its configurations. A curved plate, for instance, enhances the focus of the radiated waves but causes flexural and in-plane vibration mode coupling, which limits the design and use. The transducer's other physical properties and dimensions must be changed to avoid this hurdle and mode coupling, which may sometimes be difficult or impossible. 

A circular array layout is another example, but it has drawbacks because even minor design or size changes will impact the focal line and transducer performance.

A cylindrical shell is an alternative approach, as it can enhance the acoustic field and improve the focus of the emitted waves. Furthermore, a cylindrical design enables the transducer to be positioned in line with the incoming flow for liquid or gas sensing/actuation applications when a fluid medium is involved. These few benefits of cylindrical geometry make it a good substitute for many applications.

Application

Piezoelectric transducers are used as sensors and actuators in a wide range of industries and have advanced quickly in recent years. Because of their ease of manufacture, high energy output, lightweight, and compact size, they are frequently employed in medical engineering, aerospace, micro-robotics, ultrasonic processing, and nanometer-scale positioning systems. 

Nondestructive testing and MEMS (Micro-electromechanical Systems), including material and structural health monitoring, which includes the monitoring of metallic and nonmetallic materials and structures, make extensive use of piezoelectric transducers.

Ongoing research focuses on enhancing transducer efficiency by optimizing their design, geometry, and configurations, which can significantly impact their performance in sensing and actuation applications.

Summarizing the Key Points

  • Transducers are essential devices that convert physical quantities into electrical signals and vice versa, playing a crucial role in measurement, control systems, and data acquisition across various fields.
  • There are different types of transducers based on energy conversion, power source, and output signal type, including mechanical, electrical, active, passive, analog, and digital transducers.
  • Piezoelectric transducers are widely used in industries for their ability to convert mechanical stress into electrical signals, making them valuable in applications like sensors, actuators, and ultrasonic systems

Reference

Mieczkowski, Grzegorz, Andrzej Borawski, and Dariusz Szpica. “Static Electromechanical Characteristic of a Three-Layer Circular Piezoelectric Transducer.” Sensors 20, no. 1 (December 31, 2019): 222. https://doi.org/10.3390/s20010222.

Lin, Shuyu, and Jie Xu. “Effect of the Matching Circuit on the Electromechanical Characteristics of Sandwiched Piezoelectric Transducers.” Sensors 17, no. 2 (February 10, 2017): 329.
https://doi.org/10.3390/s17020329.

Meshkinzar, Ata, and Ahmed M. Al-Jumaily. “Cylindrical Piezoelectric PZT Transducers for Sensing and Actuation.” Sensors 23, no. 6 (March 11, 2023): 3042.
https://doi.org/10.3390/s23063042.

Instrumentation Technician. “Working Principle of Transducer? | Instrumentation Technician.” Video. YouTube, March 20, 2023.
https://www.youtube.com/watch?v=la4G7Sj4oZY.