The Research Of Cotton Moisture Content Detection Based On The Principle Of Electrical Impedance

The cotton industry is the pillar industry of China's economic development.With the rapid development of the industry,the quality requirement of the products are increasing,and the moisture content of cotton as an important index of cotton quality must be valued.In order to realize accurate and efficient measurement of cotton moisture content,the direct method with long measurement period and tedious process can not satisfy the actual measurement work.Therefore,indirect measurement of moisture content by measuring the physical properties of cotton is the future development path of the detection work.This paper study on water content measurement method of resistance-type,the main tasks are as follows:(1)This paper analyzed the conductive mechanism of cotton fiber,studies four factors that affect the conductive properties of cotton fiber,and conducts related experiments to prove it.A new method for detecting moisture content of cotton is proposed,mainly combined with the Capacitance Coupled Contactless Conductivity Detection(C~4D)technology and inductive coupling principles to form an AC measurement loop and use this to design corresponding sensor models.In order to verify the validity of the sensor model,the simulation work is carried out according to the proposed method and model by using Comsol simulation software.The validity of the designed model is verified by simulation,and the simulation mathematical mapping model was established to simulate the resistance and resistivity of cotton samples.(2)This paper designed the signal acquisition and processing system.After the conversion,filtering and amplification of the induced current generated in the AC measurement loop,analog-to-digital conversion by NI acquisition system and transfer to the computer,the resistance value is measured by using Labview software and Digital Phase Sensitive Demodulation(DPSD)technology,and the simulation experiments have also been carried out to verify that DPSD has better data processing capabilities.(3)The temperature calibration experiment of platinum resistance and the study on the relationship between moisture content and resistance of cotton were carried out.The functional relationship between temperature and platinum resistance and the mathematical model of cotton moisture regain and resistance were obtained respectively.Designed a set of simulation experiment system for measuring cotton resistance,the sample resistance values were simulated in the range of 10~5?-10~6?,after that,fitting correction was carried out to obtain a more accurate mathematical calculation model,to further verify the rationality of the design method.