Development Of Portable Impedance Detection System Based On Internet Of Things And Its Application Evaluation

Electrochemical impedance spectroscopy(EIS)has attracted more and more attention in food safety because of its advantages of fast detection and label free.Nowadays,there is an urgent need for on-site rapid screening or remote detection equipment,but the current impedance detection system is mainly imported commercial laboratory analytical instruments,with large volume and high price,which cannot be applied to on-site detection application,and limits the promotion of the detection method.In addition,with the development of science and technology,smart phones and other mobile devices have been widely used as powerful processing and control devices.Therefore,in response to the current situation and demand of impedance testing instruments,this research developed a portable impedance field detection system based on the Internet of Things and evaluated the application of the system.The main contents and conclusions are as follows:(1)A portable impedance detection instrument based on Internet of Things was developed,including a power supply module,an impedance signal conditioning module,a clock generation module,an impedance detection module and a main control module.The instrument could realize impedance detection,on-chip calculation,Wi-Fi communication and other functions.The imported commercial electrochemical workstation(Solartron 1260+1294)was used as the detection accuracy calibration instrument,and 1%precision standard resistance modules were used as the detection object.Under 200 mV excitation voltage and the frequency range from 100 Hz to 100 kHz,the maximum detection error of 100 Ω to 1 MΩ precision standard resistance modules were less than 4.2%.It shows that the developed instrument has high detection accuracy and can be used for subsequent research.(2)The impedance detection software module based on the Internet of Things was developed,which mainly includes two parts:the lower computer software and the upper computer software.The lower computer software includes the functions of impedance detection,calibration and data transmission of impedance detection data,etc.The impedance measurement algorithm was optimized and a fuzzy-then-precise gain-resistance selection algorithm was proposed,which can shorten the time consumption by up to 37.5%compared with the traditional sequential polling algorithm and realize a single measurement within 3 seconds.The upper computer software includes two parts:the MQTT message processing server and the web-side control interface:the MQTT server has the functions of data sending,receiving,processing and storage;the website has the functions of real-time display of test results,test parameter setting,and control of the testing process.(3)The feasibility of the impedance detection system based on the Internet of Things for biochemical sample detection was evaluated.The average error for the detection of different concentrations of PBS solutions was 1.70%,and the maximum error was 4.5%.Real-time impedance measurements were performed for different concentrations of Escherichia coli(abbreviated as E.coli)suspensions,and the results showed that the system could provide a response for E.coli suspensions within the concentration of 1.2×104～1.2×109 CFU/mL.The developed detection system is expected to provide a proven solution for online rapid detection of E.coli and other food safety hazards,and has certain application prospects in the field of food safety due to its compact size,high detection accuracy,and the ability to perform remote impedance detection,and cloud-based data management.