Transducer: Characteristics, Classification and selection 

Transducer (s) have become an integral part of our lives today. It is used to convert one form of energy into another. Such an energy conversion can be in the form of electrical, mechanical, magnetic, thermal or optical. It can also be visualized as having two ports where the exchange of energy occurs with the environment. This article discusses what is Transducer, its characteristics, types, applications, factors influencing the choice of a transducer and its future. It also looks into what makes an ideal transducer.

What is a Transducer

Any electrical/ electronic/ electro-mechanical device that converts one form of energy to another is called a Transducer. Some examples include Loudspeakers, Microphones, antennas, Thermometers, Pressure Sensors and Position Sensors. Although not considered transducers in the true sense, LEDs, photocells and common light bulbs also work as transducers.

Efficiency is very important for any transducer. It is defined as the ratio between the desired output power to the total input power. Mathematically, if we were to represent “P” as total input power and “Q” as required form of output power, then efficiency “E” is given by

If E% is the percentage of efficiency then,

However, it is important to note that 100% efficiency cannot be achieved by any transducer. The energy conversion process always takes away some energy. This loss is generally manifested in the form of heat.

Fig. 1 – Pictorial Representation of a Transducer

Transducers can be divided into two groups: sensors that work as monitoring systems and actuators that work by imposing certain conditions on a system. These are considered to be the most comprehensive groups of transducers. It implies that at any given moment, transducers are functioning either as an actuator or a sensor.

Few transducers function both as sensors and actuators, but, not simultaneously. Such transducers are considered as reversible. For instance, a loudspeaker (actuator) can be used to detect motions of the speaker’s diaphragm. An accelerometer is another example of reversible transducers that can be used to sense vibrations and also perform as a shaker.

Characteristics of Transducers

Below mentioned are some specifications on which the transducers are rated: –

1. Dynamic Range

It is defined as the ratio between the largest and smallest amplitude signals that can be translated by a transducer. Larger the Dynamic Range implies more sensitive and precise transducers will be.

2. Repeatability

A transducer’s ability to produce identical output upon stimulation by the same input is termed as repeatability.

3. Noise

All transducers have some random noise in their output. Small signals are largely affected by noise in comparison to larger signals.

4. Hysteresis

This is property wherein a transducer’s output is dependent not only on the present input, but, also on the previous inputs.

Transducer Types and their Applications

There are various types of transducers available in market. Few most popular and commonly used transducers are:

• Piezoelectric Transducers
• Pressure Transducers
• Temperature Transducers

Piezoelectric Transducer

This is a special type of sensor whose main function is to convert mechanical pressure into electrical energy and vise versa.

Fig. 2 – Working of Piezoelectric Transducer

Applications of Piezoelectric Transducer

The main applications of Piezoelectric Transducers are: –

• It is used in electronic drum pads to detect the sticks drummer impact. Also, it is used in a process called acceleromyography, which detects the muscle movement.
• It is known that diverse absolute pressure calculation is necessary for determining the load of an engine. Such a calculation is made possible by using piezoelectric transducers as a MAP sensor in the fuel injection systems.
• Automotive engine management systems use piezoelectric transducers as knock sensor for determining the knock of an engine.

Fig. 3 – Piezoelectric Transducers at a Glance

Pressure Transducer

It is a special type of sensor used for altering the pressure into the electrical signals. They are also called as manometers, pressure indicators, pressure sensors, piezometers and transmitters. Different kinds of pressure transducers include amplified voltage transducers, millivolt pressure transducers, and strain-gage based pressure transducers.

Fig. 4 – Pressure Transducer

Applications of Pressure Transducer

The main applications of Pressure Transducers are: –

• They are used to measure specific quantities like liquid or gas by converting pressure into electrical energy.
• They are used in altitude sensing, leak testing, pressure sensing, depth or level sensing and flow testing.
• Used for electrical power generation below the speed breakers where vehicle force is converted into electrical energy.

Temperature Transducer

This is an electronic device that converts the temperature of a device into other forms like electrical energy, mechanical energy or pressure. These converted forms are then sent to a controlling device for controlling the device temperature.

Fig. 5 – Temperature Transducer

Applications of Temperature Transducer

It is used mainly in controlling the air temperature in devices like heating, air conditioning, and ventilation.

Factors that Influence the Choice of a Transducer

The choice of a transducer used for measuring different quantities depends on many factors such as:

1. Operating Principle

The selection of transducers may be made based on its different operating principles like inductive, resistive, capacitive, piezoelectric, optoelectronic etc.

2. Operating Range

A transducer having a wide range of operation is an ideal choice because it does not break during an operation.

3. Sensitivity

It is necessary for producing the correct, detectable output.

4. Cross Sensitivity

The measure of a transducer can vary across different planes due to sensitivity. Hence, cross sensitivity is essential for accurate results.

5. Accuracy

Generally, transducers produce accurate values after calibration. A small gap for variability from desired value is permissible and is necessary for industrial applications.

6. Environmental Compatibility

A transducer must be able to perform in any environment. It must work well with shocks and high pressure.

7. Reliability and Stability

Transducers must have great stability for sustained operations. They must also be reliable in order to avoid failures or errors.

Future of Transducers

Today, transducers have a great impact on our everyday living. Some of them are quite tiny and embedded into micro-electromechanical systems. Others are quite visible and are used in smart phones, refrigerators etc. IoT has brought with it several advancements wherein transducers are predicted to impact our live even further through smarter and wireless powering capacities.

They are now being used in smart connected cars, smart home, digital twins, virtual reality, building management and healthcare. IoT has enabled more autonomy and intelligence to be moved into a transducer. This process has paved way for Artificial Intelligence, analytics and smarter applications in myriad systems.

Link to PPT: unit IV ppt.ppt