01 What is a sensor?
Sensors are devices that detect or sense physical, chemical, or biological quantities. They convert real-world information into electrical signals for further processing and transmission. This process typically involves three steps: sensing, conversion, and output.
02 Sensor classification
Sensors can be classified in several ways depending on the criterion used.
By measured target
Physical sensors, chemical sensors, and biosensors. Physical sensors measure quantities such as temperature, pressure, and displacement. Chemical sensors detect chemical substances in gases or liquids. Biosensors detect biological materials such as bacteria, viruses, and proteins.
By working principle
Resistive sensors, capacitive sensors, inductive sensors, piezoelectric sensors, and others. These operate by detecting changes in resistance, capacitance, inductance, or other physical quantities associated with the sensed parameter.
By output signal
Analog sensors and digital sensors. Analog sensors output analog signals such as voltage or current. Digital sensors output digital signals such as binary values or boolean states.
By application field
Industrial control sensors, medical sensors, environmental monitoring sensors, traffic sensors, and so on. These are used in industrial automation, healthcare, environmental monitoring, and transportation.
By manufacturing process
Mechanically manufactured sensors and non-mechanically manufactured sensors. Mechanical types include mechanical and thermal sensors. Non-mechanical types include acoustic sensors and optical sensors.
03 Working principles of sensors
The basic working steps for most sensors are sensing, conversion, and output. A sensor senses changes in the target quantity, converts that change into an electrical or optical signal, and outputs the signal to a receiver or processor.
Different sensors use different physical principles depending on the sensed quantity. For example, resistive sensors detect pressure or temperature changes by measuring resistance variations. Capacitive sensors measure capacitance changes to detect displacement or angle. Inductive sensors detect position or speed by measuring changes in inductance.
Other underlying principles include variable resistance, electromagnetic induction, and semiconductor effects. Examples include potentiometer-type and strain gauge sensors for variable resistance, inductive sensors and differential pressure transmitters using electromagnetic induction, and semiconductor-based force, temperature, or light sensors based on semiconductor behavior.
04 Applications
Sensors are widely used across many areas of daily life and industry. In smartphones, sensors enable user interaction and device orientation detection. In vehicles, sensors help perceive the surrounding environment. In industrial production, sensors enable precise process control. In healthcare, sensors are critical for monitoring vital signs, managing medications, and supporting diagnostics.
05 Future trends
As technology advances, sensors are evolving toward higher sensitivity, smaller size, greater durability, and expanded functionality. With the rapid growth of the Internet of Things (IoT), sensor deployment will expand into areas such as smart homes and smart cities. Combined with advances in artificial intelligence (AI), sensors may enable more autonomous and intelligent sensing and processing.
06 Use and maintenance
Select sensors that meet the required accuracy and reliability for the intended application. Ensure correct installation and use to avoid damage or measurement errors. Perform regular inspections and maintenance to keep sensors operating properly. Certain sensor types, such as chemical or biological sensors, may require periodic calibration and cleaning.
Summary
Sensors play a fundamental role in connecting the physical world to electronic systems. They will continue to be important across current and future applications, extending the reach of measurement and control systems and enabling better understanding and interaction with the environment.
