A sensor consists of a sensitive element, a conversion element, and a conversion circuit. The sensitive element refers to the part of the sensor that can directly sense (or respond to) the measured quantity. During the process of converting non-electrical quantities into electrical quantities, not all non-electrical quantities can be directly converted into electrical quantities using existing methods. Often, they must first be converted into another type of non-electrical quantity that is easier to convert into an electrical quantity, and then converted into an electrical quantity. For example, various types of elastic elements in sensors are commonly referred to as elastic sensitive elements.

What are the different types of sensors?

1. By application

Pressure-sensitive and force-sensitive sensors, position sensors, liquid level sensors, energy consumption sensors, speed sensors, acceleration sensors, radiation sensors, and thermosensitive sensors.

2. By principle

Vibration sensors, humidity-sensitive sensors, magnetic-sensitive sensors, gas-sensitive sensors, vacuum sensors, and biosensors, etc.

3. By output signal

Analog sensors: Convert non-electrical quantities into analog electrical signals.

Digital sensors: Convert non-electrical quantities into digital output signals (including direct and indirect conversion).  

Analog-to-digital sensors: Convert measured signal quantities into frequency signals or short-period signals (including direct or indirect conversion).  

Switch sensors: When a measured signal reaches a specific threshold, the sensor outputs a predefined low-level or high-level signal.  

4. By manufacturing process

Process-integrated sensors are manufactured using standard production processes for silicon-based semiconductor integrated circuits. Typically, the portion of the circuit used for preliminary processing of the measured signal is also integrated onto the same chip. Thin-film sensors are formed by depositing a thin film of the corresponding sensitive material onto a dielectric substrate (substrate). When using a hybrid process, part of the circuit can also be manufactured on this substrate. Thick-film sensors are made by coating ceramic substrates with a slurry of the corresponding material, typically Al₂O₃, followed by heat treatment to form the thick film. Ceramic sensors are produced using standard ceramic processes or their variants (sol-gel, etc.). After appropriate preparatory operations, the formed components are sintered at high temperatures. There are many common characteristics between thick-film and ceramic sensor processes. In some aspects, the thick-film process can be considered a variant of the ceramic process. Each process technology has its own advantages and disadvantages. Due to lower capital investment requirements for research, development, and production, as well as high stability of sensor parameters, the use of ceramic and thick-film sensors is more reasonable.

5. By measurement purpose

Physical-type sensors are made using the characteristic that certain physical properties of the measured substance undergo significant changes.

Chemical sensors are made using sensitive elements that convert chemical quantities such as the composition and concentration of chemical substances into electrical quantities.

Biological sensors are made using the characteristics of various biological organisms or biological substances to detect and identify chemical components within biological organisms.

6. By composition

Basic sensors: These are the most fundamental single-component conversion devices.

Combination sensors: These are sensors composed of different single-component conversion devices.

Application-type sensors: These are sensors composed of basic-type sensors or combination-type sensors combined with other mechanisms.

7. By mode of operation

Sensors can be classified into active-type and passive-type sensors based on their mode of operation.

Active-type sensors are further divided into action-type and reaction-type sensors. These sensors can emit a certain detection signal to the measured object, detect changes in the detection signal within the measured object, or generate a signal based on the effects produced by the detection signal within the measured object. Those that detect changes in the detection signal are called active-type sensors, while those that detect signals formed by the response are called reactive-type sensors. Radar and radio frequency range detectors are examples of active-type sensors, while photoacoustic effect analyzers and laser analyzers are examples of reactive-type sensors. Passive-type sensors only receive signals generated by the measured object itself, such as infrared radiation thermometers and infrared camera devices.