A sensor is a component or device that converts collected information into signals that a device can process. Just as humans act based on information obtained through sight, hearing, smell, and touch, devices also use information from sensors for control or processing. The signals (physical quantities) collected and converted by sensors include temperature, light, color, air pressure, magnetic force, speed, and acceleration, which utilize changes in semiconductor matter. In addition, there are biosensors that utilize biological substances such as enzymes and microorganisms. There are over 30,000 types of sensors. To fully understand sensors requires traversing almost all industrial sectors, a task akin to identifying countless stars in the sky. Common types of sensors include: temperature sensors, humidity sensors, pressure sensors, displacement sensors, flow sensors, liquid level sensors, force sensors, acceleration sensors, and torque sensors.
Sensors generally consist of a sensing element, a conversion element, a signal conditioning circuit, and auxiliary circuits. However, not all sensors must include both a sensing element and a conversion element. If the sensing element directly outputs electrical quantity, it also functions as a conversion element.
1. Sensitive element
A sensitive element refers to the part of a sensor that directly senses or responds to the measured quantity. The term "sensitive component" is an abbreviation for both sensitive elements and sensor devices; internationally, it's commonly called a sensor. However, there is a difference between a sensitive element and a sensor. A sensitive element can only detect a specific physical quantity and perform a certain function, such as piezoelectric jet gyroscopes, navigation devices for the blind, and sensors for vision, hearing, touch, force, and taste in robots. A sensor consists of a sensitive element, circuitry, a microprocessor, and mechanical structures.
Classification of sensitive elements
① Physics category, based on physical effects such as force, heat, light, electricity, magnetism, and sound.
②Chemistry-related, based on the principles of chemical reactions.
③ Biological categories, based on molecular recognition functions such as enzymes, antibodies, and hormones.
Based on their basic sensing functions, sensitive elements can generally be divided into ten categories: thermal sensitive elements, photosensitive elements, gas sensitive elements, force sensitive elements, magnetic sensitive elements, humidity sensitive elements, sound sensitive elements, radiation sensitive elements, color sensitive elements, and taste sensitive elements (some people have even divided sensitive elements into 46 categories).
2. Conversion element
This refers to the part of a sensor that converts the measured quantity sensed or responded to by a sensitive element into an electrical signal suitable for transmission and measurement.
3. Signal conditioning and conversion circuit
It can amplify, modulate, and perform operations on weak electrical signals. Furthermore, signal conditioning and conversion circuits require an auxiliary power supply to operate. Conversion circuits convert electrical parameters into easily measurable electrical signals such as voltage, current, and frequency. Examples include AC/DC bridges, amplifiers, oscillators, and charge amplifiers.
It should be noted that not all sensors must include both a sensing element and a conversion element. If the sensing element directly outputs an electrical quantity, it also functions as a conversion element, such as a thermocouple; if the conversion element can directly sense the measurement and outputs a pre-defined electrical quantity, then the sensor does not have a sensing element, such as a piezoelectric element.
Due to the diversity of measured physical quantities, the wide measurement range, the numerous physical phenomena and laws that sensing technology transforms, and the significant differences in their working environments, the types and specifications of sensors are extremely complex. At the same time, new types of sensors with different functions, structures, characteristics, and applications are constantly being researched and developed, with thousands of new types emerging every year.
Currently, sensor technology is developing rapidly. With the ever-increasing demand for measurement tasks across various industries, new sensors are constantly emerging. Simultaneously, the rapid development of new materials, microfabrication technology, and computer technology is driving sensors towards miniaturization, integration, and intelligence. Sensors are no longer just sensors in the traditional sense. The intelligent sensors that have emerged in recent years are sensors with microprocessors that combine monitoring and information processing functions; sensor intelligence is one of the main development directions of current sensor technology.
