Universal human respiratory gas detection instrument design of electronic nose (1).

<P> Introduction </ P> <P> human body fluids detected by health status, which in the clinical application has been very mature, and indeed for the diagnostic process provided very valuable information, but relies on the one hand, body fluid detection reagent ., high cost, on the other hand most of the testing method based on the "invasive" process, are not suitable for high frequency testing. .Physical health status as reflected in another way, the body's respiratory gases (pulmonary respiratory tract volatile gas and gas) can also reflect some important biological processes and metabolic information, and detection methods can, to some extent make up for lack of the former. .</ P> <P> purpose of this design is the use of the ARM7TDMI-S processor core LPC2478 system of electronic nose instrument control, analysis and gas detection signal discrimination, and the achievement of the case from the PC, .to provide a friendly graphical user interactive interface (GUI), so that users can control their own operations and record their health status. .</ P> <P> the original intention of this design is that family members can apply the system for monitoring health signs, and mainly focus on the detection of human respiratory gas in ethanol, aromatic compounds and gases out by the human digestive tract volatile .sulfide gas, amine compounds and other content, so as to alcohol, smoking populations, and the respiratory tract, gastrointestinal tract, the health status of populations is not intuitive and convenient for inspection. .Gas detection system, the signal line to achieve the principal component analysis (PCA), and because the training process requires a large number of samples, so the system of artificial neural network (ANN) on the raw data for further analysis of gas through the U disk USB Host write to .in data migration, and copy the data to the SD memory card, the user is easy to observe the results of long-term archiving. .</ P> <P> system to achieve </ P> <P> system for the detection of human respiratory gas primarily through its control efficiency of the gas can be realized. .The injection of gas, the system has two different detection methods: the higher concentration of gas, stepping motor driver six-way valve, switch to the "direct injection" state, that gas from the inlet into the chamber, in the .heating chamber in the state with the metal oxide gas sensor array (Gas Sensor Array) contact; while for lower concentration of gas, six-way valve will switch to the "absorption into the kind of" state, that gas from the inlet into the gas .Way later, in the adsorption desorption unit (EDU) were enriched in the (room temperature), and in the enrichment process has been completed, the carrier gas into the opening by the carrier gas, the gas from the marker under the EDU PID temperature control to bring out, .and into the gas chamber, this is the realization of the gas detection system, the basic principle and process of detection. .In this process, the state needs LPC2478 on gas (six-way valve switching, EDU temperature control, vacuum pump rate and gas sensor array signal sampling, etc.) for process monitoring and measurement, and through the TFT LCD, the keyboard array with the user-friendly implementation .interaction. .</ P> <P> signal after the gas is detected, the data need to LPC2478 principal component analysis (PCA), through mathematical modeling method, the design improvement of the traditional PCA algorithms, and data transformation in two .dimensional principal component coordinate system "point group", to use these point group, the sample gas in the cluster to determine the main components. .</ P> <P> in the whole process of gas detection, are needed for the gas in the gas in the flow of power, this system uses 10-bit LPC2478 DAC driver circuit of the vacuum pump to control pump speed control in achieving the .same time, the gas flow rate of gas in a more precise control, on the one hand meet the "absorption into the sample," the rate of gas adsorption process, on the other hand while maintaining full contact with the sensor when the gas sensor response time. .</ P> <P> hardware platform </ P> <P> the breathing gas detection using electronic nose prototype produced by the Guangzhou Zhiyuan Electronics Co., Ltd. SmartARM2400 development board and the project team made the expansion board to achieve gas .hardware modules of the control and analog signal pre-processing functions. .Hardware modules, including gas adsorption desorption unit, vacuum pump, six-way valves, solenoid valves, stepper motors, air chamber (TGS series of metal oxide gas sensor array), and the gas sampling bags. .System hardware design block diagram shown in Figure 1. .</ P> <P align=center> </ P> <P>.