Research On Non-contact Oil Quality Evaluation Method Based On Impedance Spectroscopy Measurement Research On Non-contact Oil Quality Evaluation Method Based On Impedance Spectroscopy Measurement

Magnetic induction detection technology is a non-contact and non-invasive electrical impedance detection technology,and multi-frequency synchronous detection can simultaneously obtain the impedance information of the tested object at different frequencies.Conductivity is an important parameter for evaluating the quality of edible oil,which is closely related to the quality of edible oil.Electromagnetic induction is an important electrical characteristic of conductive substances,which will change obviously in the course of the quality change of edible oil.The magnetic induction detection technology takes the material with different conductivity as the tested conductor and measures the change of the amplitude of the induced magnetic field before and after adding the tested conductor in the measuring area.The magnetic induction detection technology is a kind of detection principle which explains the difference of conductivity by the amplitude difference.In the detection,the pollution of the tested edible oil is avoided and the error is reduced because of non-contact,but also making the magnetic induction measurement technology in industry,medical electronics industry and environmental monitoring field has been widely used.According to the eddy current testing principle of magnetic induction characteristics,a non-contact oil quality evaluation method based on impedance spectroscopy measurement was designed in this paper.Firstly,through the research of magnetic induction measurement technology,the equivalent model of magnetic induction under multi-frequency synchronous excitation was analyzed.By analyzing the excitation mode of impedance spectrum measurement,the multi-frequency synchronous excitation signal based on Walsh function is designed.Then,using the FPGA as the excitation signal carrier,output the unipolar multi-frequency synchronous signal,and through the unipolar-bipolar conversion circuit and power amplifier circuit,the design of the signal excitation source was realized,which is used as the excitation source of the edible oil detection system to drive the excitation coil;The excitation-detection coil measurement model of the system was designed;Based on LIBVIEW development platform,a signal acquisition system was designed by using USB-6363 data acquisition card to sample and save the induction signals.By analyzing the impedance information extraction methods of FFT and APFFT,an impedance analysis method of FFT/APFFT based on the main harmonics of different frequency points was proposed.The noise level and conductivity resolution of oil detection system are used as the main performance indicators of the system.At the same time,the stability of the system was validated by experiments with different conductivity of sodium chloride solution and different kinds of edible oil samples,and the linear relationship between conductivity and amplitude difference of edible oil with different quality was obtained.The experimental results show that the method for evaluating the quality of edible oil proposed in this paper can measure the conductivity difference of the tested edible oil according to the magnitude difference and evaluate the quality of edible oil.