The Design And Implementation Of Food Safety Testing System Based On Fringing Electric Field Sensor

Fringe electric field (Fringing Electric Field, FEF) sensor is a capacitive sensor with the advantages of unilateral penetration, adjustable signal strength and tomography. The sensor is widely used in non-contact measurement of product performance. In this thesis, FEF sensor is used in food safety testing, such as water content, freshness, toxins and so on. The performance of food safety directly affects the dielectric properties of the food. The inter-electrode capacitance is changed caused by variation of the dielectric properties. The measurement system can be designed to implement food safety testing.The measurement system is based on low-power microcontroller. The power consumption of the system is reduced by simplifying the power supply voltage level, optimizing the power supply circuit, and choosing the low-power devices. The system includes sweep frequency drive module, a signal conditioning module, synchronization sampling module, human-machine interface module, serial communication module, power management circuit and so on.The adaptive band-pass filtering algorithm is proposed to improve the signal to noise ratio of the sensing output signal. The spectral analysis method is used, the MCU main frequency is corrected and the sampling frequency is selected in the different signal division to calculate the driving signal and the sensing signal amplitude, phase. The accuracy of calculation is improved.This system software is designed, including the main monitoring program, the initialization module, the interrupt module, the driver conditioning control module, the MCU main frequency setting module, the data acquisition module, the algorithm module, the man-machine interface module and the watchdog module. The main achievements contain the producing of the sweep frequency drive signal, measuring channel switching, main frequency settings, calculate the interelectrode capacitance value and the results display.The system is combined with FEF sensor to detect the moldy food. Select feedback channel capacitance value by the calibration experiment, The food safety testing and power consumption experiment are implemented, the results show that the system can distinguish OTA effectively and have advantage of low power consumption.