i. background
electronic nose (electronicnose) is a kind of olfactory simulation technology, also known as artificial olfactory, odor scanner or chemical sensor array technology. when one or more odorants pass through the electronic nose, the special signals of the odorants can be sensed by the sensor and the data can be extracted through a series of algorithms. using the special signals of different flavor substances, different gas samples can be distinguished and identified. it is widely used in the process and production control of industry and food. at the same time, some specific flavor substances can just characterize the comprehensive quality information of the sample under the influence of different raw materials, different harvesting times, different processing conditions and different storage environments, so it can also be used as food quality control and origin analysis. the electronic nose is composed of the most advanced sensor combination, suitable for detecting liquid and solid samples containing volatile substances. the earliest report of the electronic nose was in 1964 that wilkes and hartman used the oxidation-reduction reaction of gas on the electrode to electronically simulate the olfactory process. by 1994, gerdner published a review article on the electronic nose, and formally determined the concept of "electronic nose". since 1994, electronic noses have experienced rapid development for more than 20 years. nearly more than 20 research institutions specializing in electronic noses are in developed countries in europe and america. the domestic electronic nose industry has also developed rapidly. according to china's electronic nose industry in 2019 in-depth research and development prospect research report, in 2018, the output of china's electronic nose industry reached about 57,700 units, an increase of 16.1% from 49,700 units in 2016. in this context of seizing opportunities for the development of artificial intelligence, the electronic nose industry has a promising future.
ii. application
principle analysis: the electronic nose is a device with the ability to identify single and complex gases, which is composed of multiple gas sensors with overlapping performances and appropriate pattern classification methods. the working mechanism of the electronic nose is similar to the formation of human sense of smell, which is roughly divided into three levels: ① odor molecules are adsorbed by the sensor array in the artificial olfactory system to generate signals; ② the generated signals are processed and transmitted by various methods; ③ the processed signal is judged by the pattern recognition system.
1. the structure of the electronic nose:
the electronic nose is mainly composed of three functional devices: odor sampling manipulator, gas sensor array and signal processing system. among them, the gas sensor array is one of the key components of the electronic nose, which is usually composed of multiple gas sensors, and each sensor has an independent and evenly distributed air chamber.
电子鼻示意图
2. air circuit system analysis:
the electronic nose air circuit system mainly consists of a micro pump, air chamber, flow meter, pressure gauge, filter and air purification device. among them, the micro pump has two functions in the electronic nose:①collect samples; ②rinse the sensors in a row. most manufacturers separate sampling pumps and cleaning pumps because the requirements for the two are completely different. low flow and smoothness are required in collecting samples, while a certain pressure and large flow are required for cleaning the entire array of sensors.
iii. application difficulties
1. when collecting samples, low flow and smoothness are required to avoid affecting the accuracy of the test.
2. collecting samples and cleaning the entire array of sensors need to be able to regulate flow and pressure quickly and easily.
3. as a set of intelligent equipment, the electronic nose requires its main components to have remote control and communication functions.
iv. solution
1. flow pulsation solution:
①using three-chamber pump, the flow rate is more stable than single-chamber pump, such as: hilin mini pump c09 series;
①using three-chamber pump, the flow rate is more stable than single-chamber pump, such as: hilin mini pump c09 series;
2. remote control and multi-function speed regulation:
hilin micro pumps have various speed control methods, and each model includes a version with speed control function, which customers can choose for their own usage. such as: c09 series has knob speed control type, frequency speed control type and pwm speed control type. most models of hilin mini pumps have remote start-stop and speed regulation functions. for example, the 50 series and 60 series top configuration models also have 485 communication function, which is convenient for equipment monitoring.
