A Portable Pesticide Residues Detection Instrument Based On Impedance Immunosensor

Pesticides residue is not only a serious threat to food safety, but also a threat to humanhealth. The traditional pesticide residue detectors have many problems, for example operatingprocess is complicate, instruments are expensive, and need professional and technical personnel.In order to develop a portable pesticide residue detector, this paper has designed the impedancedetection system based on biological immunosensor method detecting pesticide. Main workincludes researching of characteristics of the impedance signal, designing and constructing ofthe system circuit, designing and debugging of the system software and so on.First, this paper has researched the characteristics of the impedance signal. In the practicalapplication components resistance is much more complicated than the ideal, they appearedelectrical resistance property, capacitance characteristics and inductance characteristics, andthese determine the impedance characteristics of the together. Idiosyncratic reaction ofpesticides and immunosensor changed the impedance size of the immunosensor. This paperdesigned scheme for the subsequent detection circuit, based on the characteristic ofimmunosensor.Second, this paper has designed the examination system’s hardware circuit includingimpedance detection and processing circuit, monolithic integrated circuit control system, liquidcrystal display circuit and power supply circuit. The core detection circuit was based on theAD5933chip design. The AD5933is a high precision impedance converter system solutionwhich combines an on board frequency generator with a12Bit1MSPS ADC. The chip couldget good measurement results in the test range. STC89C52was chosen to control AD5933detection circuit and LCD12864display circuit. The system circuit was need to be designedPCB and was made experimental circuit board.Third, we used the software to realize the detection circuit of the impedance signalincentive, sampling, processing and liquid crystal display. And it has used the serial port andthe STC-ISP software, the HEX document was downloaded to the monolithic integrated circuitfor debugging of the whole system combined with hardware circuit board. Combining immunesensor and detecting circuit system, detected the standard pesticides solutions of chlorpyrifos.