Design And Development Of Multichannel Breath Acetone Detector Based On WO₃-based Gas Sensor

With the continuous improvement of social economic level,people’s diet structure has undergone great changes.Both the total number and proportion of diabetics are increasing rapidly.At present,we use invasive blood glucose meter as the major diagnosis method for diabetes.However,the invasive test will not only bring diabetics a lot of pain and wounds,but also waste a lot of time and medical resources.Besides,it is inconvenient to reserve the diagnostic results.Therefore,invasive blood glucose test is not suitable for long-term monitoring of diabetes.This project designs an acetone detecting system that can be used to measure the concentration of breath acetone.We use WO₃ nanometer gas sensors with high selectivity and sensitivity as acetone detecting element,and use STM32 microcontroller and PCI-6229 data acquisition card to collect the signal of gas sensors.The main work of this paper includes hardware design,design of STM32 control program,software development of host computer and experimental test.The hardware design mainly completes the design of seven function modules,which includes STM32 minimum system,signal conditioning circuit,AD conversion and signal acquisition,dynamic resistance matching,DA conversion and gas flow control,serial port communication,power supply system.The planning of PCB layout is also a part of hardware design.System software design includes the design of STM32 control program and development of upper computer software.The SCM control program mainly includes the main program,AD acquisition subprogram and channel switch subprogram.Labview,which is a graphical programming language,is adopted in the development of the upper computer software.The functions of the upper computer software includes user interaction,signal conversion and collection,flow setting and monitoring,data display and storage.The test part completed three parts: pure acetone response test,humidity interference test and impurity gas interference test.Based on the experimental results,the test limits,responsiveness,response time and stability of test are analyzed.Analysis results show that the detection system can receive 24 gas sensor signals at the same time,the response time is about 35 seconds,the recovery time is about 90 seconds,and the minimum detection limit is less than 0.5 ppm.In addition,the detection system has rather strong anti-interference ability and good testing stability.This illustrates that the detection system can basically meet the testing requirements of breathing acetone real-time detection.