Sensors in Electrical Engineering

Sensors are the detection devices of the digital world. It senses the physical change in the environment and converts the sensed data into machine-readable or understandable language. The sensors are of two types i.e., analog and digital sensors. As the name suggests, an analog sensor provides analog values which is a set of infinite values. On the other hand digital sensor converts the data into digital signals which is a set of finite values. There are various types of sensors that are being used in various fields like the automation industry, healthcare sector, and many more.

In this article, we will study sensors, types, and practical applications.

Important Terminologies

There are various terminologies in relation to the sensors. Important terminologies are listed below:

• Sensor Resolution: Resolution means precision in representing any information. Sensor resolution means the smallest change can be detected while measuring the data.

• Sensor Deviation: It is the difference between the calculated value and the actual expected value. It is also known as sensor error. This can occur for many reasons, including environmental conditions, calibration errors, and interference.

• Sensor Sensitivity: It is the ability of the sensor to respond to even a small change that happens in the environment. It is the ability to measure the change in input parameters accurately. This characteristic helps in determining performance and effectiveness.

Classification of Sensors

There are several classifications of the sensor based on the various factors like power, detection methods, conversion phenomena, output data etc. Let’s study the classifications in more detail.

There are four types of classification of sensors:

• Based on Power
• Based on Means of Detection
• Based on Conversion
• Based on Signal

Based on Power

It is divided into two types:

• Active Sensor: Active sensors generate and emit their own energy or signals by interacting with their environment. They usually transmit signals or electricity (such as light, sound, or weak radio waves) and then measure the effect or send it back to collect data. Some example are LiDAR sensor, Ultrasonic sensor etc.

• Passive Sensor: Passive sensors are devices that detect and measure natural or external energy, events, or signals without the energy or signal itself. Instead, they rely on the environment and energy sources. Some examples are PIR sensor, Thermometer etc.

Based on Means of Detection

Another type of classification is based on the detection method used in the sensor. Some of the ways of detection includes chemical method, radiations detection, biological data interpretation, etc.

• Radiological Sensors: They are used to study and detect the radiations pattern like electromagnetic, nuclear radiations. UV sensor is one such example which is used to measure UV exposure. Another example is X-ray detectors which is used in medical imaging, etc.

• Chemical Sensors: These type of sensors is used to study the chemical properties like detecting the pH, gas concentration of a substance or material. Examples of chemical sensors are gas sensor which detects the concentration of CO2 or methane in the atmosphere. Another example is pH sensor which measures acidity or alkalinity, etc.

• Biological Sensors: They are developed to identify the biological changes in a molecule or to study its biological properties. They are used in medicines. Examples are biosensor, EEG (electroencephalogram) sensor, glucose sensors, etc.

Based on Conversion

This classification is based on the conversion i.e., how input and output are converted. Some of the types of conversion are given below:

• Thermal Sensors: It uses temperature to measure thermal changes or gradients. They generally rely on changes in electrical properties with temperature. For example thermocouples, temperature resistors (RTDs) and thermistors.

• Electromagnetic Sensors: It rely on the interaction of electromagnetic fields with the environment to detect and measure various properties, including current, voltage, and magnetic field. The examples of electromagnetic sensors include Hall effect sensors which is used to measure the magnetic field. Another example is the current sensors which is used to measure electric current, etc.

Based on Signal

This classification is based on the type of output signal is produced by sensor. It is divided into two types i.e., Analog Sensor and Digital Sensor.

• Analog Sensors: Analog sensors provide information in the form of analog signals which is continuous signals. These signals are variable and continuous and are often expressed as voltage, current or resistance levels. Analog signals are susceptible to noise and interference that can affect measurement accuracy. Some of the examples are thermocouples and thermistors for measuring temperature, measuring instruments for measuring mechanical performance.

• Digital Sensors: A digital sensor converts the data into digital signals which is a set of finite values. The information is represented in the terms of binary values i.e., ‘0’ or ‘1’. They provide the information in discrete steps. Some of the examples of digital sensors are digital temperature sensor, digital pressure sensor, etc.

Types of Sensors

Based on the above classifications, there are a variety of sensors having their unique purpose. We will study some of the important sensors in detail.

• Ultrasonic Sensor
• Proximity Sensors
• Infrared Sensor (IR Sensor)
• Temperature Sensor
• Smoke and Gas Sensors
• Touch Sensor
• Pressure Sensor

Ultrasonic Sensor

An ultrasonic sensor is a sensor that uses low-frequency sound waves (ultrasonic waves) for distance measurement, object detection, and obstacle avoidance.

Ultrasonic Sensor

Working of Ultrasonic Sensor

• The transmitter module in the sensor emits high-frequency sound waves of the frequency 40kHz or higher.
• The emitted sound waves then travel through air in the form of continuous wave.
• While travelling, when the sound waves encounters the object in its path, it get reflected.
• The sensor receives the reflected sound wave and then calculate the round trip time.
• The measurement of time helps in determining the distance to the object.
• The distance of the object is calculated with the help of the formula: Distance = (Speed*Time)/2. It is being divided by 2 because sound is making a round trip.

Proximity Sensors

It is also known as proximity switch. It is developed to detect the presence of an object within a certain range. It emits the beam of radiations and then detects the change in the field due to the presence of any object. There are various types of proximity sensors:

Proximity Sensor

Inductive Proximity Sensors: It uses electromagnetic induction to find the metallic objects within a particular range. It is used in industrial automation to detect the metallic parts moving on conveyor belt.

Capacitive Proximity Sensors: It uses the change in capacitance to detect the presence of objects. It can detect non-metallic materials like plastics and liquids. It is used in touch screens, liquid level sensing etc.

Infrared Sensor (IR Sensor)

IR sensor can detect and respond to the IR radiations. IR radiations are the type of electromagnetic radiations which has longer wavelength than visible light. It is used in the fields like detecting presence of any object due to their temperature variations.

IR Sensor

Working

• IR sensor consist of two main components i.e., emitter and a receiver.
• Emitter consist of an IR LED that emits infrared light.
• The receiver senses the IR radiations and converts it into the electrical signals.
• The strength of these electrical signal, describes about the presence of any object

Temperature Sensor

It is used to measure the temperature and convert it into readable electrical signal. This sensor is used in RTDs, thermistors, and thermocouples.

Temperature Sensor

A thermocouple consists of two different metals connected to one end. When heated, they produce a voltage proportional to the temperature difference between them. RTD uses temperature-dependent change of pure metal or metal. It is accurate and stable but it is costly. While a thermistor can change its resistance with the change in the temperature because it is temperature-sensitive.

Smoke and Gas Sensors

Smoke and gas sensors are used to detect the presence of the smoke and dangerous gases. They are very important in ensuring the safety at home and industries.

It is used to detect the smoke particles which can indicate the presence of fire. They work using a variety of technologies, including ionization and photoelectric methods, and can trigger an alert or alarm condition when smoke is detected.

Smoke Sensor

Gas sensors also detects the gases in air like methane, propene and many other pollutants. It is used to detect carbon monoxide in the home, workplace. It even measures the quality of air in the atmosphere.

Touch Sensor

It is also known as tactile sensor. It enables the device to respond to the physical touch when applied by the user. It is commonly used in smartphones. It works on the principle of the pressure. There are variety of touch sensors. Some of them are listed below:

Touch Sensor

• Capacitive Touch Sensors: It works when capacitance changes. The capacitance change due to inductive object like our fingers touch the screen of the phone.
• Resistive Touch Sensors: It is made of two flexible layers. There is a space between the two flexible layers. When pressure is applied, the top layer comes into contact with the bottom layer which causes change in the performance.

Pressure Sensor

It measures the pressure applied on any surface. It works on the principle of like piezoelectric, resistive and capacitive. When the pressure is applied, it is converted into the electrical signals.

Pressure Sensor

It finds its application in variety of industry like aerospace, automotive, etc. Accuracy and reliability are important characteristics of pressure sensors as they are frequently relied upon to measure accuracy and safety in many applications. The ability to measure altitude can improve performance, efficiency and safety in many applications.

How are Sensors Used?

We are using sensors in our everyday life nowadays. Their main function is to identify, measure and convert physical, chemical or biological signals into electronic or digital signals. Sensors are used in:

• Industrial Automation: Sensors monitor machines in production, ensuring accuracy, safety and efficiency. Proximity sensors, encoders and pressure sensors play an important role.

• Space Exploration: During space exploration, sensors collect data from Earth and spacecraft for navigation and research.

• Medical: Sensors are used in medical devices to monitor vital signs, detect diseases, assist in surgery, and assist in monitoring and diagnosis.

• Automotive Technology: Cars rely on sensors for features like collision avoidance, cruise control, and tire monitoring to improve safety and operation.

• Agriculture: Soil moisture, light and temperature sensors enable good agricultural practices to improve crops and utilize resources.

The Future of Sensor Technology

The sensor technology is advancing day by day and will lead in the improvement of the following:

• Internet of Things: The Internet of Things (IoT) is growing with the coming years as sensors are becoming the backbone of devices, networks, and systems. This interaction will support the development of smart homes, cities and businesses by offering improved energy, energy consumption and data analysis.

• Miniaturization and Consolidation: Due to technology advancement, sensors will become smaller and smaller. This trend will facilitate their integration into various devices, from gadgets to smartphones, smart clothing and even the human body. Miniaturized sensors will enable better data collection, real-time monitoring and more precise control.

• Artificial Intelligence and Machine Learning Integration: Sensors will be used with artificial intelligence and machine learning algorithms to understand the big data they produce. This integration will enable changes to applications such as predictive analytics, vulnerability detection and predictive maintenance, illegal driving and usage.

Applications

• Automotive Industry: It is used in the automotive industry where it is used in lot of applications like parking assistance, obstacle detection, engine temperature measurement, and monitoring engine performance, etc.
• Consumer Electronics: Sensor finds its application in consumer industry like, smart phones, gaming interactions, turning off the screens during phone calls, and autorotation, etc.
• Healthcare: Sensors finds its wide applications in the healthcare sector. It is used in measuring heart rate, pulse, blood sugar levels, and thermometers, etc.
• Industrial Automation: It is used in industrial automation where it is used in monitoring hydraulic and pneumatic systems, robotic arms position detection and conveyor belts, etc.
• Agriculture: It is used to optimize irrigation, monitoring weather conditions, watering of the plants, and tracking the farming equipment, etc.

Advantages and Disadvantages

Some of the advantages and disadvantages of sensors are:

Advantages

• Automation: Sensors automate tasks, increasing efficiency and reducing human intervention.
• Improve product quality: During production, sensors control product quality and consistency.
• Security: Sensors are important security components such as burglar alarms and security cameras.
• Save Costs: Sensors help reduce costs by preventing waste and improving resource utilization.
• Research and Exploration: Sensors play an important role in scientific research, and space exploration by providing the proper and precise data.

Disadvantages

• Cost: High-quality electronics can be expensive, which can hinder the adoption of some applications.
• Power Consumption: Continuous operation of the sensor drains the batteries in mobile devices and IoT sensors, requiring charging or replacement.
• Impact of sensitivity to environmental factors: Some sensors are sensitive to temperature, humidity and other environmental factors, which can affect their performance.
• False alarms: Sensors can produce false readings, causing false positives or false positives.
• Privacy issues: Sensors in smart devices and surveillance can cause privacy issues when misused or stolen.

Conclusion

In this article, we have seen that the sensors are used in various fields currently. They are revolutionizing the industries. The sensors are used in various fields, making human reach possible, while earlier it is not possible. The sensors collect the data, process it, and convert it into the machine understandable language, which helps to store the data, and further data analysis can be done to study the trends. Sensors will provide us smarter and more sustainable future.

Frequently Asked Questions

1. What are the common sources for the error that occur in sensor?

The error caused by the sensors can be due to lots of factor. One such factor is measurement error. Another factor can be temperature or humidity.

2. How Internet of Things (IoT) has been impacted by the sensors?

Sensor collects data from devices, process it and sent it to cloud for analyzing the trends. That’s why sensors are an important part of IoT. They enable interaction and the use of electricity between modern devices and machines.

3. How are sensors calibrated?

Sensors are calibrated by comparing their output with known reference values or standards. Calibration helps ensure accuracy and reliability in sensor measurements.