Security Sensors: Types, Working Principles, and Applications

This article explores the fundamentals of security sensors, their various types, and their applications across different domains. It covers the working principles of motion sensors, ultrasonic sensors, tomographic sensors, wireless sensors, chemical sensors, and magnetic sensors.

Introduction

Technological advancements have unfortunately led to increased threats and vulnerabilities to human lives, with rising crime rates making people feel unsafe without adequate security systems. Electronic security sensors play a crucial role in addressing these concerns. While CCTV surveillance systems are widely known, this article delves into other sensors and systems used in national, home, personal, industrial, and cybersecurity applications.

What are Security Sensors and Their Applications?

Security sensors are devices designed for security applications. Here’s a breakdown of their use across various sectors:

• National Security: Radar, satellites, UAVs (Unmanned Aerial Vehicles), security robots, and electro-optical sensors.
• Home Security: Motion sensors and CCTV systems.
• Personal Security: Panic alarms, child locators, mobile SOS buttons, and implantable microchips.
• Industrial Security: Fire alarms, chemical sensors, access control systems (RFID, NFC, biometric), video surveillance systems, and intrusion detection systems.
• Cybersecurity: Artificial Intelligence (AI) combined with sensors and Machine Learning (ML) techniques to minimize data theft and other malicious activities.

Working Operation of Different Types of Security Sensors

Here’s a look at various types of security sensors based on their construction and how they work:

Motion Sensors

Motion sensors often employ infrared, ultrasonic, or radio frequency technologies.

Motion Sensors using microwave frequency or infrared frequency

• Motion sensors are classified into active and passive types. These sensors trigger alarms upon detecting human beings or animals. They are typically installed outside houses, sensing movement and alerting the owner or security team.
• Active motion sensors emit radio frequency in the microwave region and analyze the reflected signal to detect motion. These are known as microwave motion sensors.
• Passive motion sensors (PIR - Passive Infrared) detect infrared radiation emitted by human or animal bodies. When a person or animal enters the sensor’s range, the sensor detects the thermal energy, triggering the alarm.

Ultrasonic Sensors

• Ultrasonic sensors use ultrasonic frequency waves.
• They consist of a transmitter and a receiver. The transmitter converts electrical energy into sound waves, while the receiver captures the echo and converts it back into electrical energy to determine the distance of an object. Hence, it is also known as a distance sensor.
• Ultrasonic waves are beyond the hearing range of humans but can be heard by animals. The transmission of these frequencies can deter animals from the protected area.

Tomographic Sensors

Tomographic sensors operate on radio frequencies. They emit radio waves and detect disturbances as they pass between nodes in a mesh network. Their ability to penetrate walls and obstructions makes them suitable for large areas like warehouses.

Wireless Sensors

Wireless sensors use communication standards such as RFID, Wi-Fi, Bluetooth, NFC, Zigbee, and Z-Wave. Security systems using these sensors are often referred to as smart security systems. Users can monitor and control these systems via smartphone apps, enabling control over doors, windows, surveillance cameras, lights, smoke detectors, and sirens.

Chemical Sensors

• Chemical sensors transform chemical information (composition, element/ion presence, concentration, etc.) into an analytically useful signal.
• They consist of a chemical (molecular) recognition system (receptor) and a physicochemical transducer. The receptor interacts with analyte molecules.
• These sensors are used in medicine, environmental pollution monitoring, and home safety.
• They can detect organic compounds in gases and have applications in radio frequency detection, sensing toxic materials, vapors, bomb detection, and chemical agent simulants.
• An ideal chemical sensor should be inexpensive, portable, and foolproof.

Magnetic Sensors

• Magnetic sensors are classified based on their measurement approach, whether measuring magnetic flux density in a specific direction or the total strength of a magnetic field.
• They are used for detecting ferromagnetic and conducting objects, navigation, position tracking, linear/angular position and rotation sensing, and anti-theft systems.
• Magnetic sensors are developed using technologies such as coil, fluxgate, SQUID, Hall effect, optically pumped, nuclear precession, giant magneto-resistance, anisotropic magneto resistance, giant magneto impedance, and piezoelectric composites.

Other Security Sensor Types

• Biometric Access Control Systems: Gesture detectors, fingerprint sensors, and face recognition systems.
• RFID-based Proximity Access Systems: Commonly used in offices, factories, banks, and government establishments.
• Implantable Microchips: Used in livestock tracking and for child safety, providing location information.