The Research Of Wind Tunnel Wind Speed And Gas Concentration Testing System Based On LabVIEW

Virtual instrument technology can complete all kinds of test and measurement by using high-performance modular hardware and combining with highly efficient and flexible software. The development of the virtual instrument technology is largely improving the performance of the test system. In complete complex automation testing, virtual instrument test system has incomparable advantages than the traditional testing system, and even in some case that the traditional test system is unable to complete, virtual instrument test system still can meet the test requirements. It is also because of the huge advantage of virtual testing system, makes the application of virtual testing is more and more widely.The virtual instrument technology is used in this paper to design a set of wind speed and gas concentration measurement system that be used in Simulation of underground engineering wind tunnel to test the wind speed and the concentration of the gas in this wind tunnel. Wind speed and gas concentration measurement system mainly includes two parts:hardware and software. Hardware mainly includes the wind speed and gas sensors, signal conditioning circuit, data acquisition equipment and computers; Lab VIEW of the NI company is used to design the software of the test system, the software include login module, data acquisition module, historical data query module, alarm module and alarm information query module. These modules have met requirements of the test system for data acquisition, storage, display and alarm.Wind speed sensor, MAVS02, is developed by Institute of CETC group13and the gas sensor, MQ-4type of semiconductor gas sensitive element is the production of Zhengzhou WeiSheng. The PCL-8181data acquisition card is produced by Advantech and there are16analog signal input and12bit A/D converter in this kind of data acquisition card. The operational amplifier LM324is produced by TI and the filter chip MAX29of filter circuit which is a kind of low pass switched capacitor filter is made by MAXIM. The output signal of the sensors are amplified by amplifier circuit and filtrated by filter circuit and then collected by data acquisition card, the computer display and storage the data that collect by DAQ card.Environmental temperature and humidity changes have strongly influence on sensor sensitivity and zero voltages, therefore there is the study on characteristics of the sensor and then the least square method is used to sensor’s sensitivity and zero drift compensation to increase the stability and precision of the test system. A number of functions are developed by Advantech to fit its DAQ card. By using these functions, we can easily set up data collection system and reduce programming difficulty. In the test system, LabSQL toolkit is used to operate of the database, and it would be pushing the collected data into database, it is convenient to read the data in the future. Wind speed and gas concentration waveform display interface and numerical display table are designed on the LabVIEW front panel, which can show the different channel data we chose. Historical data query module can playback the waveform and data of the past. If the wind speed and gas concentration exceed the setting value, the test system will automatic alarm and storage the alarm information into the database. The historical alarm information query module can playback the alarm information. Finally, the standard deviation of the test system is analyzed. The results show that the measurement standard deviation is small and data acquisition system is stable.