Design Of Liquid Auto-sample System Used For Biochemical Detection

The purpose of this paper is design an auto-sample system for biochemicaldetection, which includes auto-sample device, heat device and temperature controldevice. While biological analysis instrument developing, sample is still in manual.The auto-sampler system can greatly improve the detection accuracy and efficiency,but seldom study in the world. According to the analysis about related papers wefound that the preprocessing of existing analytical instruments needed is samebasically, so in this paper we designed the auto-sample system used for milkdetection and we aimed to make it has board applicability.The design of auto-sample system in order to reduce dead volume and bubbles,facilitate dispensing function and improve detection accuracy, so sampling, mixingand thermostat structure were designed. In this paper STC89C52RC was chosen ascontrol chip, based on it hardware and software were designed used to control heater,step motor and display. The main content and process of subject are as follows:First, access to relevant literature summarized the commonly used treatmentmethods of current sampling methods and biochemical analytical instruments beforetesting. According to the needs of milk detection program was developed, and thesuitable sampling, mixing and peristaltic pumps driving methods ware chosen. Thendesigned heating mode and heating tank based on those temperature controlalgorithm was studied.Second, hardware circuit and software program ware designed. STC89C52RC ischosen to be MCU. Stepper motor drive circuit designed to provide peristaltic pumpsampling power and sampling precision control. Constant current source andmodulator circuit designed to convert resistance variation with temperature to avoltage value. Design AD7705analog-digital conversion circuit and stable voltagesource circuit, then which is connecting to microcontroller used for temperaturecontrol. Data acquisition device is used to build the heating model of the water tank,simulate the model with fuzzy-PID control algorithm by MATLAB to get the a decision table of proportion parameter, integral parameter and differentialparameter, then control water temperature based on this decision table. To control theentire sampling process, ASSR1611control circuit has been designed. At last,assembly of the entire system, which include the aforementioned parts, LCD andsolenoid valve which is used to select channel.Third, experimental analysis of auto-sampler and temperature control device. Inthis section analysis sampling accuracy, sampling error and sampling speed. At lastanalysis and calculate the accuracy of temperature controlled.