Sensors and Transducers

In this tutorial, you will learn the basics of Sensors and Transducers which include their definition, types, classification, and their working details. You will also learn about the difference between Sensors and Transducers as well as their manufacturing and real-time applications.

Contents:

  1. What is a Sensor?
  2. What is a Transducer?
  3. Types of Sensors
  4. Types of Transducers
  5. Sensors vs Transducers
  6. How is a Sensor Manufactured?
  7. Real-time Application of Sensors
  8. Real-time Application of Transducers

What is a Sensor?

A sensor is a device that is used to measure a certain physical parameter or a non-electrical quantity. It measures them and converts the measured value to an electrical parameter such as resistance, capacitance, inductance, etc. Then the output can be converted to voltage or current later for easier measurement and analysis.

Every sensor has a sensing element that measures the quantity, and it differs from one type of sensor to another.

The generalized working of a sensor is as follows:

Input and Output Forms of a Sensor

The above diagram is a clear representation of a sensor. Any non-electrical quantity such as temperature, pressure, force, motion, etc will be sensed by the sensor and it will be converted into its equivalent electrical forms like resistance, capacitance, and inductance most of the times.

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What is a Transducer?

A transducer is not a single module but is a combination of a sensor and a signal conditioning circuit.

As mentioned before, it is necessary to convert the output of a sensor into current or voltage to make it easily usable. A transducer is a device used for this purpose so that the user does not need to condition the sensor’s output.

The below diagram explains the internal components of a transducer.

Internal Components of a Transducer

As shown in the above figure, a transducer has a sensor and a signal conditioning unit. Both combined will receive the same input as a sensor and before providing the output, the signal conditioning circuit converts the sensed parameter to current or voltage signal for further analysis.

Types of Sensors

  • All the sensors available in the market cannot be classified into a single classification. Instead, sensors are divided into various categories according to various parameters. Thus, a single sensor can fall into two or more types.
  • Most sensors are classified as resistive, capacitive, and inductive type sensors based on the type of output they provide when input is given to them.
  • Other major classification of sensors is analogue (or) digital sensors and active (or) passive sensors. An analogue sensor provides an integer or a decimal as an output while a digital sensor just prints a binary digit (1 & 0).

The following diagram shows some of the common classifications and examples of sensors.

Classifications and Examples of Sensors

From the above diagram, one can see that the thermistor is categorized as resistive, analogue and passive while an X-Ray sensor falls under both analogue and active sensor type. The same goes for a piezoelectric sensor which is passive and analogue and in the case of an IR sensor, it is a passive sensor, a digital sensor and is an optical sensor as well.

The above-mentioned are just some of the sensors and most of the sensors in the market will be categorized within these classifications.

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Types of Transducers

Like the sensors, transducers also have a different classification according to the nature of output they provide, whether it requires an external power supply or not, whether it can be used to conserve energy. Sometimes a transducer is classified based on its application too.

Most transducers are used in automation, control systems, etc. At those times, transducers will not be of a single module, instead, it’ll be an integrated circuit of two or more components. Those transducers will not have a distinct classification.

Sensors vs Transducers

The following table describes the difference between a sensor and a transducer.

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Parameters Sensor Transducer
Definition A sensor is just a measurement device that is used to measure a physical change or a parameter. A transducer measures a physical parameter such as pressure, displacement, flow etc. and converts it into another form of energy (mostly electrical).
Components A sensor is a single module that has a sensing element as its major component. A transducer is a combination of a sensor and a signal conditioning circuit in which the conditioning circuit plays the major role.
External Requirements No other external circuit is needed for the functionality of the sensor. A converter circuit is mandatory most of the times.
Integration Integrated into the inner circuit of the system. Used in the output part of a system.
Functionality All sensors are transducers most of the time. All transducers need not be a sensor.
Examples Temperature sensors, Pressure sensors Hall effect transducers, Piezoelectric transducers

How is a Sensor Manufactured?

A sensor is not a single module as it seems to be. Instead, it is a consolidation of two or more simple circuits. A single sensor consists of many components like an inbuilt power source, a sensing element, some connecting wires, etc. All those components are integrated into a single chip like structure giving the sensor the appearance of a single module.

In the diagram below, the manufacturing process of an IR sensor is explained.

Manufacturing of an IR Sensor

IR Sensor: An infrared sensor (IR sensor) is a device that is commonly used to measure the amount of heat emitted from an object. It can also be used as a detector for black colored objects which is used in some engineering projects such as a line follower robot or an obstacle avoider robot.

  • This infrared sensor consists of two LEDs, in which one emits infrared radiation and the other receives the reflected radiation.
  • There is a distance trimmer that is used to calibrate the distance of the object, a 5V dc power supply and three-input pins.
  • All the above components are connected and soldered in an empty IC wafer made up of silicon and are connected using wires creating a single sensor. This IR sensor is also known as an obstacle sensor.

Real-time Applications of Sensors

  • The temperature sensor is one of the most used sensors. This sensor is used in almost every field in our day-to-day lives. A temperature sensor plays a vital role in human temperature monitoring these days. A pyrometer (a device that finds the temperature of an object without any physical contact) is one of the best applications of the temperature sensor.
  • Proximity sensors play an important role in the field of automation. For instance, smart homes use proximity sensors in the doors which results in the opening of the door when some human motion is detected.
  • The security level of the above-mentioned smart homes can be increased by installing a fingerprint sensor along with the proximity sensor, which allows the user to scan their fingerprint. If the biometric matches, then the door will be opened.
  • Another commonly used sensor is an accelerometer. An accelerometer is used in almost every automobile. It is used to measure the dynamic distance and speed of a vehicle. It is also used to measure the vibration level, inclination etc.

Here is a diagram which depicts various applications of Temperature Sensor.

As shown in the above figure, computers, mobile phones, electric iron, coffee machines and other such electrical and electronic devices come with an inbuilt temperature sensor that monitors the temperature of the internal circuit of the device regularly.

Real-time Applications of Transducers

  • Sensors and transducers are interdependent most of the time. It varies with the simple fact that the sensor just senses or measures a parameter while a transducer senses it and converts it into another form.
  • The application of the temperature sensor is already discussed above. The usage of a temperature transducer is almost similar with a small twist.
  • Temperature transducer measures the temperature of an object and converts it into an electrical signal. Then the signal is sent to an external circuit used to control that object’s temperature.
  • This kind of transducers can be used in the food industry to measure the temperature of the raw materials, processed food, etc. to maintain the correct temperature for the food.
  • This kind of transducers also used in air conditioners.
  • A transducer inside the air conditioner constantly measures the temperature of the atmosphere and controls the temperature of the air through the machine accordingly.

Key Points to Remember

Here is the list of key points we need to remember about “Sensors and Transducers”.

  • A sensor provides resistance, capacitance, or inductance as output as a transducer provides an electrical parameter as output after reading a physical parameter.
  • Sensors are classified based on various parameters. Yet, the most used classification is active/passive, analogue/digital.
  • Transducers are also classified into active, and passive based on the requirement of an external power source.
  • Though a sensor and a transducer may seem like two different modules, they are correlated to each other.
  • A transducer will have a sensor in it and a sensor can act as a transducer if needed.
  • Sensors and transducers are not only meant for electrical and electronics, but they are very useful in the field of biology too.
  • Many sensors and transducers are used in the day-to-day lives of a human being.

If you find any mistake above, kindly email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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