Design of Gas Sensors Circuits with in-System Programmable Ddevices

In-system programmable devices are products that combined modern electronic techniques and semiconductor techniques.They are indispensable devices in designing modern circuits and systems.This paper presents two practical circuits designed with programmable devices and its design method.By introducing programmable devices into gas sensor circuits,we can further improve system reliability,stability,sensitivity and integration degree,and enhance flexibility of system design.

Quantitative research of the liquid film characteristics in upward vertical gas, oil and water flows

The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.

Wet Gas Meter Development Based on Slotted Orifice Couple and Neural Network Techniques

A slotted orifice has many superiorities over a standard orifice. For single-phase flow measurement, its flow coefficient is insensitive to the upstream velocity profile. For two phase flow measurement, various characteristics of its differential pressure （DP） are stable and closely correlated with the mass flow rate of gas and liquid. The complex relationships between the signal features and the two-phase flow rate are established through the use of a back propagation （BP） neural network. Experiments were carried out in the horizontal tubes with 50ram inner diameter, ooerated with water flow rate in the range of 0.2m^3·h^-1 to 4m3·h^-1, gas flow rate in the range of 100m^3·h^-1 to 1000m^3·h^-1, and pressure at 400kPa and 850kPa respectively, where the temperature is ambient temperature. This article includes the principle of wet gas meter development, the experimental matrix, the signal processing techniques and the achieved results. On the basis of the results it is suggested that the slotted orifice couple with a trained neural network may provide a simple but efficient solution to the wet gas meter development.

Uncertainty analysis of flow rate measurement for multiphase flow using CFD

The venturi meter has an advantage in its use,because it can measure flow without being much affected by the type of the measured fluid or flow conditions.Hence,it has excellent versatility and is being widely applied in many industries.The flow of a liquid containing air is a representative example of a multiphase flow and exhibits complex flow characteristics.In particular,the greater the gas volume fraction（GVF）,the more inhomogeneous the flow becomes.As a result,using a venturi meter to measure the rate of a flow that has a high GVF generates an error.In this study,the cause of the error occurred in measuring the flow rate for the multiphase flow when using the venturi meter for analysis by CFD.To ensure the reliability of this study,the accuracy of the multiphase flow models for numerical analysis was verified through comparison between the calculated results of numerical analysis and the experimental data.As a result,the Grace model,which is a multiphase flow model established by an experiment with water and air,was confirmed to have the highest reliability.Finally,the characteristics of the internal flow Held about the multiphase flow analysis result generated by applying the Grace model were analyzed to find the cause of the uncertainty occurring when measuring the flow rate of the multiphase flow using the venturi meter.A phase separation phenomenon occurred due to a density difference of water and air inside the venturi,and flow inhomogeneity happened according to the flow velocity difference of each phase.It was confirmed that this flow inhomogeneity increased as the GVF increased due to the uncertainty of the flow measurement.

Environmental Analysis with 2D Transition-Metal Dichalcogenide-Based Field-Effect Transistors

Field-effect transistors(FETs)present highly sensitive,rapid,and in situ detection capability in chemical and biological analysis.Recently,two-dimensional(2D)transition-metal dichalcogenides(TMDCs)attract significant attention as FET channel due to their unique structures and outstanding properties.With the booming of studies on TMDC FETs,we aim to give a timely review on TMDCbased FET sensors for environmental analysis in different media.First,theoretical basics on TMDC and FET sensor are introduced.Then,recent advances of TMDC FET sensor for pollutant detection in gaseous and aqueous media are,respectively,discussed.At last,future perspectives and challenges in practical application and commercialization are given for TMDC FET sensors.This article provides an overview on TMDC sensors for a wide variety of analytes with an emphasize on the increasing demand of advanced sensing technologies in environmental analysis.

Realization of Rapid Debugging for Detection Circuit of Optical Fiber Gas Sensor： Using an Analog Signal Source

An optical fiber gas sensor mainly consists of two parts： optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of^the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer （SCM）, an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

Metal oxide semiconductor gas sensing materials for early lung cancer diagnosis

The urgency of early lung cancer(LC)diagnosis and treatment has been more and more significant.Exhaled breath analysis using gas sensors is a promising way to find out if someone has LC due to its low-cost,non-invasive,and real-time monitoring compared with traditional invasive diagnostic techniques.Among sensor-based gas detection techniques,metal oxide semiconductor’s gas sensors are one of the most important types.This review presents the-state-of-art in metal oxide gas sensors for the diagnosis of early LC.First,the exhaled breath biomarkers are described with emphasis on the concentration of abnormal volatile organic compounds(VOCs)caused by the metabolic process of LC cells.Then,the research status of metal oxide gas sensors in LC diagnosis is summarized.The sensing performance and enhancement strategy of biomarkers provided by metal oxide semiconductor materials are reviewed.Another effective way to improve VOC detection performance is to build a gas sensor array.At the same time,various gas sensors combined with self-powered techniques are mentioned to display a broad development prospect in breath diagnosis.Finally,metal oxide gas sensor-based LC diagnosis is prospected.

气体传感器的一组测量电路

报道了气体传感器测量的一组优化电路，它由可以直接输出气体传感器工作电阻Rg随微量有毒、有害气体浓度C变化的曲线化为直线的拟合电路组成，配以计算机的数据处理，可进行还原性气体的定量分析．

Parameters optimization of π-phase-shifted long-period fiber grating for gas sensing

The gas-sensitive film coated π-phase-shifted long-period fiber grating(LPFG),consisting of two same long-period fiber gratings cascaded by a regular fiber with length of half of the grating period,is proposed for gas sensing.The sensitivity of the sensor is defined by the change rate of the transmission at specific wavelength with respect to the film refractive index.The qualitative and numerical analyses show that to get a high sensitivity,the optimal coupling strength of each long-period fiber grating is √2 π/4.With this coupling strength,the longer the grating is,the higher sensitivity the sensor has.By choosing appropriate grating period,a high sensitivity for the film with a certain refractive index and thickness can be attained.

超声波热量表流量测量系统的研究

在使用积分仪系统计算流量的过程中,大部分超声波热量表需与供暖水接触,易受温度和密度等流体条件影响并存在模拟开关不断切换的问题。基于此,文中采用体积流量超声波测量的方法,开发低成本高精度的超声波热量表测量仪。文中结合工程实际,在简要介绍超声波热量表的原理和安装实验测试分析的基础上,对系统中各部分的设计电路进行了详细叙述。实验结果表明,合理使用超声波热量表,可有效保证测量的精度,使管道不易堵塞,使用寿命增长,功耗降低,值得大范围推广。