What is Transducer? – Working, Types and it’s Application

What is a Transducer?

What is Transducer


What Does the Definition of a Transducer Entail?

We know that energy can transform from one form to another. On top of that, a signal can change from one state to another.

A transducer is a device that converts any physical quantities into a proportional electrical signal (voltage and current). In general words, the transducer is a device that converts one form of energy into another which is measurable in the form of an electrical signal. That process of converting energy from one form to another form is known as Transduction.

Whereas, an electrical transducer is a device that converts any physical quantities (such as pressure, temperature, level, displacement, etc.) into a proportional electrical signal (voltage and current) so that it can be easily handled and transmitted to measuring instruments. Some commonly used electrical transducers are loudspeakers, thermometers, microphones, etc.

A transducer’s primary usage lies at the boundaries or borders associated with the various aspects of diverse measurements, automation, and even control systems. For instance, the device can come into use for scenarios where there is a need for converting an electrical signal into another form. It can be of some physical quantity or value. It can consist of torque, force, motion light, position, etc. On the other hand, the reverse case also applies in such situations.

Is the Transducer a Sensor?

Since both the Transducer and Sensor are used to detect the change in the environment or item they are attached to, one common confusion that arises in our mind is Transducer and the Sensor both are the same or different. Well, the answer is No. Transducers and Sensors are not the same there are some differences between them. The main difference between the sensor and the Transducer is:

A sensor senses the physical quantities in the environment and produces the output in the same form. Whereas the Transducer detects the physical quantities, converts them, and then produces output in the form of an electrical signal (voltage and current).

Why do we need a Transducer?

To measure the exact magnitude of any physical quantities  (such as pressure, temperature, level, displacement, etc.) is very difficult. But if we convert these physical quantities into proportional electrical signals (voltage or current), then we can easily measure their magnitude with the help of various electrical measuring instruments. The primary function of the Transducer is to convert physical quantities into corresponding electrical signals so that it can easily transmitted to the measuring instruments. Hence a Transducer is needed for converting physical quantities that have to be measured.

Advantages of converting physical quantity into electrical signal

These are various advantages of converting physical quantity into an electrical signal.

  • An electrical signal can easily and efficiently be processed using various electrical circuits and microcontrollers.
  • A small amount of power is required for controlling and processing the electrical signal.
  • An electrical signal can easily be amplified and controlled and it can be visually displayed on a time and magnitude scale.
  • Information can easily be stored in the form of electrical signals and also it can be used whenever it is needed.

Parts and Working of Transducer

In general, the Transducer works on the principle of Transduction. Whereas Transduction is the process of converting input physical quantities into proportional electrical output signals.

Working of Transducer

A Transducer uses sensors and a signal conditioning unit to perform transduction functions. In other words, we can say that a Transducer is the combination of a sensor and signal conditioning unit.

The Sensor unit is responsible for detecting any changes in input physical quantities that have to be measured. The output of the sensor is always non-electrical in nature. Whereas the signal conditioning unit converts the output of the sensor into an electrical signal proportional to the magnitude of the input.

Classifications and Types of Transducer

What are the Classifications into Which a Transducer can be categorized? Like most other electrical devices, a transducer can also be of varying kinds and types. Their categorization can remain based on a few specific elements and parameters. The classification can depend on the particular work the gadget does. The manner or way in which the transducer performs the conversions and operates may also play a role. Based on the mentioned factors, the classification of a transducer can entail two primary types, which consist of the following:

Electrical Transducer 

As the device’s name may suggest, an electrical transducer changes physical quantities into electrical signals. The conversion initiates from some other form or type of energy. The various examples of electrical transducers consist of microphones and loudspeakers. On top of that, a thermocouple is a notable example of an electrical transducer. It generates a voltage of a specific value by converting the temperature differences existing in the primary system. 

Mechanical Transducer 

A mechanical transducer gives a mechanical value or energy form as its output. The electrical device initiates the transformation or conversion process from a specific and targeted physical quantity. The various examples of mechanical transducers comprise membranes, ring balance manometers, metallic diaphragms, capsules and bellows, etc. Metallic diaphragms, capsules and bellows, and membranes target displacement and convert it into a mechanical value.  On the other hand, metallic diaphragms work on and deal with both displacement and strain as their targeted physical quantities.  Besides the two mentioned types and their classification parameters, other categorization factors also exist. They depend primarily on the inputs and outputs utilized by the transducers. Based on that, the new classifications consist of the following:

Input Transducer 

An input transducer, more commonly known as a sensor, picks up a specific form or state of physical energy and converts it into a readable signal. For instance, a microphone captures the produced or generated sound waves. It then works on them to change them into an electrical signal. It enables the device to transfer them to an amplifier. It is possible with the help of a stable wire connection.  Another example of an input transducer consists of a pressure transducer. It works primarily on physical forces and converts them into a value or quantity that other appliances can measure and comprehend. 

Output Transducer 

An output transducer, more commonly known as an actuator, is a device that takes on a working style, principle, and result generation, which is the complete opposite of an input transducer. Let us put it in simpler terms. The former works on electrical signals and uses them as input, unlike the latter. On top of that, it converts them into some other form of energy or state as the output.  Let us take the example of a lamp to understand the concept better. It works on electricity and converts it into light energy. Hence, the electrical signal gets transformed into another form.  Similarly, a motor transducer also uses electricity to produce mechanical energy. The output can be coupled with any dynamic object to generate or create motion. It can consist of blades, wheels, vehicles, mobility devices, etc. 

Difference between Active  and Passive Transducer

What are the Various Points of Difference between an Active Transducer and a Passive Transducer? An active transducer is a unique type or category of transducer that works on any form or state of energy that is not electrical. In other words, it utilizes non-electrical values as the input and converts them into electrical ones. Thus, the output generated is a specific amount of current or voltage. The device makes it possible without using external power or energy sources. Hence, an active transducer is often called a self-generating transducer.

On the other hand, a passive transducer does the same thing as an active transducer. However, it requires an external power or energy source. The gadget’s input parameters can undergo a few alterations in such cases. It may be due to the input signal. It, in turn, can bring about changes in the inductance, capacitance, or resistance. The need for an external power or energy source implies that an output transducer is not ‘self-generating.’ Thus, the device is also known as an externally powered transducer. 

Now, let us deliberate on the differences between an active and a passive transducer. 

  • Working Principle 

An active transducer operates by using a measured source and generating or deriving the required amount or quantity of energy. On the other hand, a passive transducer uses energy or power from some external source. The device then uses the values to modify and change its physical properties and get the required output. 

  • Resolution and Quality of Output 

The output produced by an active transducer is generally of high quality and resolution.  Comparatively, the output produced by a passive transducer is conventionally not of high quality and resolution. 

  • State of Generated Output 

The output generated by an active transducer comes in the form or state of electrical current or voltage.  On the other hand, the output generated by a passive transducer comes in varying quantities. It primarily depends on the related passive elements. On top of that, the change remains associated with it. 

  • The Complexity of Conversion Process and Transducer Design

The conversion process and transducer design associated with an active transducer are generally simple and uncomplicated. However, the conversion process and transducer design linked with a passive transducer are intricate, demanding, and complex. 

  • Additional Amplification Requirement

An active transducer needs a specific extent or degree of additional amplification to operate or work.  On the other hand, a passive transducer requires no additional amplification. 

  • Examples

Examples of an active transducer encompass a thermocouple, piezoelectric crystal, photovoltaic cell, etc.

A few examples of a passive transducer comprise a differential transformer (LVDT and RVDT), photomultiplier tube, resistance strain, etc.

Characteristics of Transducer

These are mainly two types of characteristics of the Transducer that decide the overall performance of the Transducer.

  1. Static characteristics
  2. Dynamic characteristics

Static characteristics

Static characteristics don’t depend on the input signal in other words it doesn’t vary with variation in input signal or with time. Some of these static characteristics are:

  • Accuracy: The accuracy of any electrical instrument is the maximum difference between its measured value and actual value. It is expressed in a percentage of actual value. The transducer must have high accuracy to measure the quantity correctly.
  • Linearity: The ability to change the output linearly with the input is known as linearity. In this case, the output becomes proportional to the input signal. Any Transducer having good linearity characteristics gives a more accurate reading.
  • Repeatability: The ability of the Transducer to generate an identical output multiple times when the same input signal is applied.
  • Stability: Any Transducer should provide stable output without any fluctuations.
  • Sensitivity: It is the ability of the Transducer to detect the smallest change in physical quantities and effectively convert it into an electrical signal known as sensitivity. A device having higher sensitivity can measure more accurately and precisely.
  • Robust: A Transducer must be able to withstand extreme environmental conditions and mechanical stress.

Dynamic Characteristics

These are some dynamic characteristics of the Transducer that depend on time and vary accordingly.

  • Dynamic range: It is the ratio between the highest amplitude and the lowest amplitude the Transducer can efficiently convert. A Transducer with having high dynamic range has better performance and sensitivity.
  • Speed: The speed of the Transducer plays a vital role in its performance as it indicates how quickly it converts physical quantities into a stable electrical signal.
  • Error: It is the difference between the actual value and the measured value. It can be caused by various factors. A Transducer having a minimum error is considered as best.
  • Noise: It is a random unwanted electrical signal that distorts the original signal. A low-amplitude signal is more affected by noise than a high-amplitude signal.

Processes and Steps for Calibrating a Transducer

The steps and processes associated with calibrating a transducer are more or less the same irrespective of the different and diverse types and kinds of the device. Thus, let us focus on a single one and deliberate on it. The methods linked to the calibration of a pressure transducer entail the following:

  • The first step begins with the use of a manometer. The users can use the gadget to assess and record the two mercury levels on the curved ends. It helps get the pressure value. For instance, suppose the standard and minimal pressure for a particular setup is 120 mm of mercury. Then, the users can note one of the values at 150 mm and the other at 90 mm. 
  • The users have to increase the pressure of the manometer in specific situations. It gets done primarily when the measurement remains related to a transducer that comes filled with fluid. 
  • Next, the users need to read the control signal using a meter and note it down. One essential thing to remember here is that no digital displays should be used. 
  • After that, the users must work with the device or appliance with which the transducer remains connected. They have to power it on and set its voltage reading to the required value. The transducer’s readings or measurements should be taken once more and noted. 
  • Lastly, the users need to compare the two readings, one that they took at the beginning and the other that they recorded at the end. In addition, they can change or alter the values as many times as necessary. On top of that, they can contrast the two readings more than once. This approach helps get a precise and accurate idea of any error if it exists. 

Methods and Steps of Testing a Transducer

Conventionally, the checking and testing of a transducer start with the evaluation, measurement, and calculation processes. It gets done on the device’s fundamental physical dimensions. Next, the shorts, continuity, opens, and so on get tested using a series and sequence of uncomplicated methods.  The role of the electrical measurements is to ensure that the transducer remains void of or free from significant faults and defects. For instance, it may remain linked to parameters and factors such as loss or capacitance. The tests are essential and compulsory. Thus, they should get done before moving on to assembling the transducer. After that, the device can be used conveniently.

The functional testing processes associated with a transducer should be carried out under ambient conditions. It should be of the temperature, pressure, etc. Generally, the assessments encompass gauging the value of the pulse echo generated in air or water. It gets created at a specific distance and then bounces or reflects off a given target. The bandwidth, ring-own, and sensitivity values are noted and recorded during the process.

In several cases, the Total Acoustic Power (TAP) value linked with the transducer also gets measured during this period. In the last step, the device gets placed under the fixed and required operational and environmental conditions associated with its construction and design. Once again, it gets tested on multiple parameters, and their readings get noted.

The functional tests consist of constraining and driving a transducer. It can be done with a pulse, sine wave, spike, or square wave. The selected option depends on the required, preferred, and intended use. Under usual circumstances, a traditional industrial pulse receiver can be used for the job.  In some cases, an amplifier can also find an application here. The return signal and pulse can be observed and viewed on an oscilloscope. The predominant purpose is to develop numerical measurements for checking the subjective values and parameters of cleanliness, standard, or quality. It is generally of a required waveform.  For instance, the testing of a pressure transducer can be done using the following steps:

  • Firstly, the Users have to connect the +ve lead of the transducer to the +ve lead of the power supply system. 
  • Then, they need to connect the –ve lead of the transducer to the +ve lead or terminal of the multimeter. 
  • Next, the Users have to connect the –ve lead of the millimeters to the –ve lead of the power supply system. 
  • After that, they have to check the display on the transducer to get the readings under no load conditions. The depicted values of the measurement should show current with its magnitude in a fixed range. Generally, it should be between 4 milliamperes to 20 milliamperes. 
  • The transducer has some faults or defects if the computed values do not come in the estimated range. In such cases, it should be corrected or repaired according to the specific requirements to ensure precise and appropriate results.

Efficiency of Transducer

Like other electrical devices, Transducer efficiency is also defined as the ratio of output power in the desired form to its physical input power. No Transducer has 100% efficiency due to its large amount of power losses in the conversion process.

Advantages and Disadvantages of Transducer

Advantages of Transducer

  • Since there are no mechanical complications it reduces the mechanical wear and tear problem.
  • It required very little electrical energy to process electrical signals thus more energy efficient.
  • Electrical signals of the Transducer can be very easily and quickly processed by using various electrical circuits and microcontrollers.
  • Electrical signals are easy to transmit and receive over a long distance.

Disadvantages of Transducer

  • In long-term uses, Transducers are not as reliable as mechanical instruments.
  • Noise in electrical signals can affect the accuracy and performance of the Transducer.
  • Some Transducers which are more accurate and precise are very expensive and costly.
  • Some battery-operated Transducers’ performance is affected by the charge remaining in the battery.

Uses and Applications of Transducer

Conversion of any physical quantities into proportional electrical signals is required in almost every field. So here are some common applications of Transducer listed below.

  • In antennae, Transducers are used to convert electromagnetic waves into an electrical signal for receiving and transmitting data over long distances.
  • In medical instruments such as ECG, ultrasound machine, MRI, thermometer, acceleromyograph,  CT scan, etc.. Various Transducers are used to convert signals generated by the body into electrical signals.
  • Transducers are also used to measure the pressure and volume of any liquid and gas.
  • It is also used to measure the weight and load of any large and heavily loaded vehicles.
  • In civil engineering, Transducers are used to measure the stress of buildings bridges, etc.

Examples of  Transducer

What are the various examples of Transducers used in Various Scenarios?

A Transducer is perfect for usage across multiple sectors and industries. A few well-known examples of Transducers in everyday applications of gadgets consist of the following:

  • Electromechanical:
    • Rotary Motors
    • Galvanometers
    • Tactile Sensors
    • Potentiometers
    • Load Cells
    • Accelerometers
  • Electroacoustic:
    • Piezoelectric Crystals
    • Gramophone Pickups
    • Loudspeakers
    • Earphones
    • Ultrasonic Transceivers
    • Sonar Transponders
  • Electro-Optical:
    • Cathode Ray Tubes (CRTs)
    • Fluorescent Lamps
    • Photomultipliers
    • Photodiodes
    • Phototransistors
    • Incandescent Lamps
  • Electrochemical:
    • pH probes
    • Electro-Galvanic Sensors
    • Hydrogen Sensor
  • Electromagnetic:
    • Magnetic Cartridges
    • Antennas
    • Hall Effect Sensors
  • Thermoelectric:
    • Thermistors
    • Thermocouples
    • Resistance Temperature Detectors (RTDs)
  • Radio-Acoustic:
    • Radio Receivers
    • Transmitters
    • Gieger-Müller Tubes

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Hey, I'm Satish Gupta an Engineer by profession and blogger by passion. I am writer and founder of this blog, Here I publish contents related to Electrical and Electronics Engineering..

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