Study On Key Technologies Of Automatic Sampling System In Biochemical Analyzer

With the continuous improvement on quality of life,residents’ demands for medical care are becoming higher and higher,leading to a surge in the number of biochemical tests in hospitals,testing centers and other institutions.Biochemical analyzer is one of the most commonly used devices to detect hepatic function,renal function,blood glucose and blood lipids level,so the demand for it is very large.At present,however,most of the domestic biochemical analyzers in use are imported products.Therefore,it is urgent to develop more advanced and easy-to-use domestic biochemical analyzers.Automatic sampling system is one of the most important function modules of biochemical analyzers,and it is mainly used for automatic sampling of samples and reagents,disposing of waste liquid and cleaning colorimetric curettes and reagent probes.Therefore,the performance of the sampling system will directly affect the overall performance of the biochemical analyzer.Based on the above background,this thesis designs a set of automatic sampling system for biochemical analyzer.The system realizes the functions of antomatic and high-accuracy sampling for samples and reagents,automatic rinsing of standard 96-well plates,automatic disposal of waste liquid and automatic stoarge and read of sampling data,etc.Besides,the key factors affecting the sampling accuracy are studied.The main work includes the following three parts:(1)The sampling system is designed,including the host and slave computers.The design of slave computer is mainly devided into the following three aspects.Firstly,transmission module and liquid path of the system are designed.Secondly,the hardware control circuit is designed,including power module and position control module of the 96-well plates and reagent probes,start-stop control module of pumps and electromagnetic valves.Thirdly,control software of the slave computer is programmed,including serial communication,the control of pumps and valves and sampling sequence control.In addition,the functions of man-computer interface for the host computer mainly includes the setting of sample and reagent sampling volume,the setting of rinsing times for 96-well plates,and background storage and access of sampling data,etc.(2)The factors affecting the performance of sampling accuracy are studied and analysed via software simulation.The S-shape curve is selected to drive the stepper motor of the plunger pump,because it can achieve smooth change of accelerated velocity and is more in line with the torque-frequency characteristics of the stepping motor.The Logiscic function is introduced to optimize the traditional driving curve of plunger pump and three optimized S-shaped driving curves of stepper motor are proposed.Besides,the performance of three optimized S-curves is simulated and analyzed via Fluent software.The simulation results show that when r value(the parameter determining the shape of Logistic function)is 0.6,the sampling performance of curve is the best.Secondly,because the sampling process contains high viscosity liquid such as serum and low viscosity liquid such as rinsing liquid,in order to study the influence of liquid viscosity,three kinds of different viscosity liquid,ethanol,water and glycerin,are selected as the research objects.Liquid state in the sampling probe is simulated via Fluent software.The simulation results show that the liquid with high viscosity and small Reynolds number is not easy to flow out of the probe when the flow velocity is the same,and it will remain in and on the outlet of the probe after the sampling,which will affect the sampling accuracy.Finally,the influence of the liquid flow velocity on the sampling accuracy is studied by using the simulation method.The simulation results show that increasing the flow velocity of liquid with low viscosity can inhibit the formation of satellite droplets and improve the sampling accuracy.However,increasing the flow velocity of liquid with high viscosity will increase the liquid residue in the probe after the sampling operation and reduce the sampling accuracy.(3)Exprimental research and analysis of the factors affecting the sampling accuracy are carried out,including experiment of pure water filling the sampling pipe,experiment of reverse clearance determination for plunger pump,experiment on material hardness of sampling pipe,experiment on the volume of air column,sampling experiment of three S-curves for acceleration and deceleration,experiment on maximum running velocity of plunger pump.Besides,the sampling scheme is finalized according to the experimental results.The experimental results show that the sampling accuracy can be improved by filling the system liquid in the sampling pipe,choosing the hard pipe as the sampling pipe,adopting the driving curve with r value of 0.6 and selecting the appropriate maximum running speed of the plunger.