Research progress on electronic nose sensing technology
As an emerging intelligent sensory instrument, the electronic nose realizes the quality evaluation of the test object by simulating the human olfactory system, and mainly qualitatively or quantitatively detects the gas or volatile components through the odor fingerprint information. Different "odor fingerprints" information of different flavor substances can be used to distinguish and identify different gas samples. In addition, certain flavor substances can justify the comprehensive quality information of the sample under different multi-variable effects such as different raw material origin, different harvest time, different processing conditions and different storage environments. It has been used in food, medicine, materials, environmental protection and other industries. In recent years, the application of electronic nose technology in related fields has been continuously expanded, showing a good application prospect.
Shanghai Baosheng Electronic Nose c-Nose is a combination of the most advanced sensors. It is the electronic nose with the best stability and the highest detection accuracy of similar instruments. Ideal for testing liquid and solid samples containing volatile materials. The product uses a metal oxide semiconductor conductance type gas sensor in an electrically conductive gas sensor.
principle:
Metal oxides such as SnO 2 , ZnO, Fe 2 O 3 and WO 3 are N-type semiconductor materials, and there are a large number of holes on the surface of the sensitive film. At 300-500 ° C, they are easily H 2 , CO, CH 4 and The reduction gas such as H 2 S is reduced, and the sensitive film is electron-derived, and the conductivity changes. For a particular gas, the amount of change in conductivity is related to the gas concentration.
A polymer material having electrochemical properties, after adsorbing a gas, generates an electron density of a polymer molecular chain, which in turn causes a change in the conductivity of the gas sensing material, which is related to the type and concentration of the analyte.
Features:
By adding a precious metal such as platinum during the preparation process, the operating temperature of the metal oxide gas sensor can be lowered and the sensitivity can be increased. At present, the sensor manufacturing process is very mature, the stability is good, and the product is highly commercialized. Other types of sensors are still in the development stage.
Other types of sensors are:
1. Organic polymer film conductance type gas sensor
The organic polymer membrane gas sensor which belongs to the conductivity type has high sensitivity, can work at normal temperature, and has small volume. However, the production process is time consuming, and its conductivity is greatly affected by the preparation process. There is drift phenomenon during detection; the ground humidity is sensitive, the sensitivity to low polarity gas is low, and the detection range has certain limitations.
2. Mass sensitive gas sensor
An acoustic wave signal is generated by an alternating electric field acting on the piezoelectric material, and a signal of the detected object is obtained by measuring a change in the acoustic wave parameter. It is mainly suitable for the detection of organic gases, but its signal-to-noise ratio is small, circuit requirements are more complicated, and repeatability is difficult to guarantee.
3. Fiber optic gas sensor based on the principle of spectral change
By optical characterization, the most straightforward measurement method is to detect changes in the absorbance of a target gas over a specific frequency range.
It has strong anti-noise ability and high sensitivity, but the control system is more complicated and costly. The fluorescent dye is affected by white light and the service life is limited.
4. Metal oxide semiconductor field effect transistor gas sensor based on charge power consumption
The leakage current is changed when the sensitive membrane interacts with the gas, which changes the performance of the sensor. By analyzing the change, different gases can be detected and analyzed. Quantitative detection of CH 4 , CO 2 , NO 2 , and organic gases. However, the chip is not easy to package and integrate, and there is a reference drift, which is monotonous and inferior to other sensors.
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