Research On Blood Coagulation Detection Dystem Based On The Principle Of Bioelectrical Impedance

With the gradual maturity of bioelectrical impedance(BI)technology,more and more researchers use it to detect various physiological index.With the shortcoming of high sample consumption and low sensitivity,various blood coagulation detector(BCD)based on the blood physicochemical properties have emerged.Therefore,the detection of coagulation factor reaction time(CFRT)based on the BI principle has important reference value in disease diagnosis.This thesis introduces the development status of BI technology and traditional BCD technology.The method of this system was lead according to those measurement methods and principles.Based on electrical characteristics of blood,the overall design scheme of BCD system with BI was proposed with theoretically analyzing the blood three-element equivalent circuit and the principle of coagulation impedance measurement.The thesis completed the hardware and software design of the BCD system.The realized hardware with STM32F103 as MCU and AD5933 as measurement unit includes the modules of power supply,temperature control,motor control,impedance measurement and CAN communication.The embedded software mainly includes fuzzy PID algorithm,integral separation PID algorithm and AD5933 impedance measurement.Simultaneously,PC-end software was developed to send function commands,receive data,draw curves and curve fitting based on the one-dimensional median filtering algorithm.For system verification,the standard RC parallel network with different frequencies and the 100Ω standard resistor with sweep frequency was measured and the errors were less than 1%.A detection method of CFRT was designed that obtained by locating the abscissa of the first step point of the second derivative of the impedance data,which reflects the coagulation status.Actual blood measurement results show that the precision error was less than 3% and the repeatability and reproducibility error was less than 5%.It is proved that the system could be used for CFRT detection with high precision and sensitivity,good repeatability and reproducibility.