The sensor is generally composed of four parts: a sensitive element, a

conversion element, a conversion circuit and an auxiliary power supply. The

sensitive element directly feels the measured element and outputs the physical

quantity signal that has a definite relationship with the measured element. The

conversion element converts the physical quantity signal output of the sensor

into an electrical signal; The conversion circuit is responsible for amplifying and

modulating the electrical signal output by the conversion element. Conversion

elements and conversion circuits generally require auxiliary power supply. The

function of the sensor is often compared with the five major human sensory organs:

Light sensor - Vision

Acoustic sensors - Hearing

 Gas sensor - Smell

 Chemical sensor - Taste

 Pressure sensitive, temperature sensitive, fluid sensor - touch

 Classification of sensitive elements:

 Physics, based on physical effects such as force, heat, light, electricity, magnetism and sound.

 Chemistry, based on the principles of chemical reactions.

 Biological, based on molecular recognition functions such as enzymes, antibodies, and hormones.

                Generally, according to its basic sensing function, it can be divided into ten categories such

as thermal elements, photosensitive elements, gas sensitive elements, force sensitive elements,

magnetic sensitive elements, humidity sensitive elements, acoustic sensitive elements, radiation

sensitive elements, color sensitive elements and taste sensitive elements