Internet of Things (IoT) refers to the use of various information sensors, radio frequency identification (RFID) technology, global positioning systems, infrared sensors, laser scanners, and other devices and technologies to collect information in real-time from any object or process that needs to be monitored, connected, or interacted with. It gathers required information such as sound, light, heat, electricity, mechanics, biology, and location. Through various possible network accesses, it achieves ubiquitous connections between things and things, and things and people, enabling intelligent perception, identification, and management of objects and processes. IoT is an information carrier based on the Internet and traditional telecommunications networks, allowing all ordinary physical objects that can be independently addressed to form an interconnected network.

Sensor technology is equivalent to the “ears” of the IoT. Sensors are extremely common when building the IoT. So, what are the sensor classifications used in the IoT?

Sensors in the IoT are mainly responsible for receiving the “sounds” of objects and the environment. Without sensors to collect information, subsequent control cannot be realized.

Specifically, information collection involves converting measured quantities such as temperature, humidity, light, voltage, and current into usable output signals. However, IoT devices are often located in harsh natural environments where sensors face severe environmental tests; therefore, the requirements for sensor technology are more stringent.

Currently, sensors are mainly divided into ultrasonic sensors, infrared sensors, laser scanners, millimeter-wave radars, and stereo vision cameras.

Traditional sensor classifications mainly include: resistive sensors, inductive sensors, capacitive sensors, piezoelectric sensors, magnetoelectric sensors, thermoelectric sensors, photoelectric sensors, digital sensors, optical fiber sensors, ultrasonic sensors, thermal sensors, analog sensors, etc.

If distinguished by different directions, the classification of sensors also varies:

By use: pressure-sensitive and force-sensitive sensors, position sensors, liquid level sensors, energy consumption sensors, speed sensors, acceleration sensors, radiation sensors, and thermal sensors.

By principle: vibration sensors, humidity-sensitive sensors, magnetic-sensitive sensors, gas-sensitive sensors, vacuum degree sensors, biosensors, etc.

By output signal: analog sensors, digital sensors, pseudo-digital sensors, and switch sensors.