Design Of Measurement System For Human Physiology Key Parameter

The total water content of human body is the sum of the amount of intracellular fluid plus extracellular fluid.The amount of intracellular fluid is related to the balance state of body fluid,which can reflect the health state of human body.An imbalance of body fluids often leads to dehydration and edema,which is often associated with other diseases,such as kidney disease,liver disease,and heart failure.So the disease can be monitored by measuring the fluid status of the patient.The existing body fluid detection techniques include X-ray,CT and so on.These methods are costly,testing devices cannot be worn,and patients cannot be continuously monitored for a long time.Bio-resistance method has the characteristics of low cost and contact measurement,which can easily measure the fluid content inside and outside human cells,so as to monitor the body fluid balance state.Based on the mature theory of biological resistance method at home and abroad,this topic mainly completes the following work:(1)Several methods of measurement system design of human physiological key parameters measurement system are compared,the final selection of the more commonly used is four-electrode measurement method.On the basis of bioelectrical impedance theory,the Cole-Cole impedance circle theory and the analysis method of human body impedance measurement are introduced in detail.(2)Design the hardware structure of the system including two parts: impedance measurement control circuit,impedance measurement circuit.The method of measuring the human body impedance is to inject the safety current into the biological tissue first,and then detect the voltage and current value of the corresponding circuit through the sampling electrode.The voltage signal is changed into digital signal through the analog-to-digital converter,and then the impedance value of the corresponding part of the human body is calculated by the FPGA for data processing.After the MCU control circuit obtains the impedance value,the frequency control word is sent to the FPGA.The FPGA switches the frequency and begins to measure the impedance value of the human body at the next frequency.At the same time,the MCU control circuit also controls the access electrode,so as to achieve segmentalized impedance measurement of different parts of the human body,and through the impedance value to calculate the amount of fluid inside and outside human cells.(3)In order to coordinate the various modules of the control system,a single-chip microcomputer control system is designed to control the impedance measurement process through human-computer interaction,which can realize the measurement frequency conversion and the selection of measurement sites.Timed measurement can be achieved,so as to achieve round-the-clock monitoring of patients.