Design Of A Portable Food Safety Detector Of Controlled Temperature

With the development of science and technology, the aggravation of environmental pollution and the widespread use of chemical substances, food safety accidents are increasing year by year. There is a close correlation between food security and human health, and now food safety has become a global problem with the globalization of food trading. Food safety problems has attracted the attention of the relevant departments of China, as a result, to strengthen the supervision and management of food safety become one of the important tasks of all levels of government. One of the most effective way to process the food safety problem was discovering and processing earlier, curbing it before eaten by people. Then the food safety testing instruments emerged so as to implement the food safety testing work and effectively prevent food safety things from happening.Food safety testing instrument is for testing the poison and the harmful material content. At present, the food safety testing are mainly focused on traditional methods which has some disadvantages, such as, long detecting time and only for substances at ambient temperatures, limiting the application scope to a great extent and not suitable for rapid detection on the spot. This paper designed a temperature controlled portable food safety testing instrument based on the current status of food safety testing instruments in China and the development tendency of domestic and international testing technology.The instrument is of low cost, easy operation, fast speed and small in size, which can choose different reaction temperature according to different testing substances and is appropriate for rapid food safety testing on the spot. This portable temperature controlled food safety testing instrument was based on PIC single chip, the temperature controlling was with the DS18B20temperature transducer and the semiconductor heating/cooling pieces. The system consisted of microprocessor, optical source module, data acquisition module, temperature controlling module and display module. And the microprocessor using the PIC16F877 single chip which had ample I/O interfaces and strong port drive ability with 3 timer/counters and 2 CCP modules simplifying the external interface circuit, mainly realizing system reset,choice of monochromatic light source and temperature controlling, etc. Optical source module was employing the beam splitting system of the halogen tungsten lamp and the prism add stepper motor, and the monochromatic light was got through the rotation of the prism controlled by the stepping motor. The data acquisition module chose the TSL230 optical frequency converter to accomplish the light intensity-frequency conversion without former light intensity-current and then digital signal conversion to further reduce the instrument volume. And the temperature controlling module collected and controlled the reaction temperature. Finally, the display module showed the result.In order to verify the whole performance of the instrument, the concentration of sodium nitrite and formaldehyde solution were measured. The result showed that the testing time was less than 30 minutes and the measurement error was below 10%. The degree of accuracy was accord with the national standard, demonstrating that it can be used to the rapid detection of the food safety.