Ceramic Based Resistive Sensors

This paper reviews the current status and research trends of two types of ceramic based resistive sensors, thermistors and gas sensors. The issues and challenges associated with their development for high temperature applications are examined and discussed. Worldwide research efforts in ceramic based resistive sensors, devoted mostly to resolve the issues of selectivity and stability, are also reviewed. These efforts tend to integrate the results obtained from both empirical and basic science approaches, and focus on various stages of sensor development, including development of new material systems, sensor fabrication and manufacturing techniques, and smart sensor arrays.     

Electrostatic deposition of CVD particles for fabrication ofultrafine ceramic filter

A novel method for forming a ceramic membrane was devised. Ultrafine particles of silicon nitride synthesized by thermally activated chemical vapor deposition (CVD) were deposited on an outer wall surface of a porous ceramic tube (substrate) by electrostatic force and sintered in an inert gas atmosphere. The ceramic-made electrode assembly using surface discharge was used for charging ultrafine particles at an elevated temperature. Special ceramic membranes with a three-dimensional network for use as a fiber filter were obtained by this method. The effective pore size was around 0.2-1.0 μm in diameter, and its porosity was extremely large. This structure has the advantage of allowing microfiltration with a very low pressure drop     

Calibration methods of carbon nanotube gas sensor for partial discharge detection in SF/sub 6/

The authors proposed a new type of gas sensor for high sensitive detection of decomposition products generated by partial discharge (PD) in SF/sub 6/ gas. The sensor employed carbon nanotubes (CNTs) as gas sensing transducer and was fabricated by electrokinetic manipulation of CNTs using dielectrophoresis. Due to complicated gas decomposition process of SF/sub 6/ gas, calibration of the CNT gas sensor is an essential and challenging subject in order to realize reliable and stable detection of PD under practical conditions. In this paper, two methods for the CNT gas sensor calibration were proposed and tested. The first method was based on initial conductance dependence of the CNT gas sensor response. The CNT gas sensor response to PD increased almost linearly with the amount of CNT trapped onto the sensor electrode, which could be quantified by the initial conductance of the sensor. However, the calibration accuracy of this method was about 50 % and was not high enough for practical use. The second method employed NO/sub 2/ (nitrogen dioxide) as calibration gas because of the similarity in the CNT sensor response to PD decomposition products and NO2. It was found that the accuracy of the NO/sub 2/ calibration was about 10 % and far better than the first method. Finally, effectiveness of the NO/sub 2/ calibration was demonstrated by a PD monitoring test in which two CNT sensors were simultaneously exposed to SF/sub 6/ decomposition products with identical concentration.     

Gas discrimination method for detecting transformer faults by neural network

This paper describes a method available for early detection of abnormality in an oil-filled transformer. In this method, four gas sensors having different characteristics and neural network are used to identify gas species (H₂, CH₄, C₂H₄, C₂H₂ and mixture of two species). To improve the selectivity of gas sensors, the time response patterns induced by changing sensor temperature and the stationary sensor output are identified by neural network. Furthermore, the mixture ratio of gases is derived by using the stationary sensor output in response to the changing sensor temperature. Gas species are well discriminated, and the mixture ratio derived from the sensor output agrees well with the measurement by gas chromatography. Therefore, it is confirmed that our method is applicable to the transformer diagnostic technology.     

基于气体扩散模型的气体源定位系统

为了快速准确地确定气体泄漏源的位置,利用无风连续泄漏点源浓度的扩散模型,提出了基于加权质心算法的气体源定位法。采用气敏传感器阵列对目标区域的气体浓度进行检测,并通过ZigBee无线传感器网络把收集的数据反馈给协调器,协调器把打包好的数据传递给主处理器,处理器依靠测量的结果计算出气体源位置,并可视化显示。在目标区域为4 m×4 m,以乙醇蒸汽为实验目标气体进行气体源定位实验。结果表明,平均定位结果相对误差不超过6%,验证了该方法的准确性。     

Using sensor networks for highway and traffic applications

Wireless sensor networks have been used for a variety of applications. However, many highway and traffic applications have not been tapped, primarily sensor networks for highway and traffic algorithms that alleviate generic problems such as highway congestion. This is due to the fact that sensor network technology is a very recent development. Since sensor networks are relatively new, not many applications have been explored in depth. Utilizing the new generation of TinyOS micaboard mote sensors, miniaturized sensors that utilize TinyOS, an event-based operating environment written in code similar to stylized C, the article focuses on how to achieve the best possible data results from sensor network applications and setups for traffic/highway goals. How to use sensor-network graphs for optimal placement of sensors in a network so as to minimize work and to achieve the best possible, and most accurate, signal-strength localization measurements is also be a primary focus. Also discussed is a method that optimizes the tradeoff between energy and accuracy using a variety of activation policies. Finally, simulations and distancing experiments of indoor and outdoor data are provided to encourage similar sensor work.     

一种SF6气体中水份含量在线测量的方法

介绍了一种SF6气体中微水含量在线测量的方法,系统以相对湿度、温度和压力为特征量,分别以湿度、温度和压力传感器实现对特征量信号的提取,经过现场数据处理后传送至计算机,利用计算机实现对数据的最终分析和显示。经测量表明,传感器工作正常,能反映SF6气体中的水份含量,能达到测量的目的。     

SF6气体中微水含量在线监测方法

介绍了一种SF6气体中微水含量在线监测的方法。监测系统以相对湿度、温度和压力为特征量,分别以湿度、温度和压力传感器实现对特征量信号的提取,经过现场数据处理后传送至计算机,利用计算机实现对数据的最终分析和显示。该系统的实际测量表明:传感器工作正常,能准确反映SF6气体中的水分含量。     

石英挠性加速度计的压膜阻尼分析

石英挠性加速度计是导航与制导系统中常用的一种惯性元件,其表头阻尼影响加速度计的动态性能但相关研究却鲜有报道,基于此提出一种适用于石英挠性加速度计的压膜阻尼分析方法。根据石英摆片的形状和转动规律建立雷诺方程,采用时域有限差分方法在摆片上的非规则区域内求解压强分布和阻尼力矩,进而得到阻尼系数为1.69×10-4Nms/rad,对应阻尼比为12.75。计算阻尼比与系统参数辨识实验得到的阻尼比11.57相近,证明提出的压膜阻尼分析方法有效可行,该方法可以为石英挠性加速度计及类似惯性传感器中的阻尼分析与设计提供指导。     

Measurements of equivalent salt deposit density (ESDD) on a suspension insulator

Equivalent salt deposit density (ESDD) is widely used to describe the state of contaminated insulators. In this paper, a new method of ESDD on-site measurement is studied. Two types of sensors are designed, which can not only carry enough water for the contamination on the insulator surface to dissolve and cover the insulator surface with conducting solution, but also measure the conductance of the solution. The design of the sensors and the determination of the desired parameter are introduced in detail. Experiments prove that the conductance of the contamination solution is linear with the square root of ESDD of the insulator. This relationship can also be deduced by Debye-Huckel-Onsager theory. According to this relationship, the conductance measured by the sensor can be converted to ESDD. Therefore, Measuring ESDD on-site can be realized.     

一种在线分析变压器故障特征气体的智能传感器

在线监测变压器油中溶解气体可有效地分析变压器绝缘状况,在线监测用气体传感器是实施该技术的关键。针对半导体气体传感器的交叉敏感特性,提出了将气体传感器阵列与人工神经网络技术相结合,利用6个半导体气体传感器组成传感器阵列,采用BP神经网络进行模式识别。大量的试验证明,所提出的智能传感器可有效地提高H2,CO,CH4,C2H4,C2H2,C2H66种气体的分辨率和检测灵敏度。     

一种新型碳纳米管气体传感器的响应特性研究

基于碳纳米管(CNTs)气体传感器的SF6气体分解产物检测技术,是诊断GIS绝缘缺陷引起的局部放电的有效手段。开展传感器对SF6分解气体响应特性的研究,对于将该技术应用于GIS局部放电的监测具有重要意义。笔者测量了CNTs气体传感器对4种标准气体(HF、SO2F2、SOF2/S2OF10、SO2)的响应,并建立了由GIS模拟罐体、基于脉冲电流法的局放仪和CNTs气体传感器构成的实验系统,测量了CNTs气体传感器对局部放电形成的SF6分解气体的响应,研究了传感器在多次测量中的重复性以及其响应随局放的变化规律。结果表明,在SO2F2和SOF2/S2OF10气体环境中传感器响应特性明显,且对SO2F2更加灵敏;SO2和HF则基本不引起传感器的电导变化。传感器能够成功检测到针板电极模型引起的局部放电,传感器的电导值随着放电时间的增加而逐渐增加,其响应也随着局部放电能量的增加近似呈线性增加的趋势,最终传感器响应出现饱和趋势。传感器的测量具有重复性,两次测量相差低于0.5%。SF6气体分解产物的气相色谱及红外光谱分析证实了上述结果的合理性。文中使用的标准气体浓度较低,因此关于SO2和HF无法引起传感器响应的结果仍需要利用高浓度标准气体进一步验证。     

Modelling of chemical surface acoustic wave sensors and comparative analysis of new sensing materials

Comparative analysis of different, new gas sensing materials in surface acoustic wave chemical sensors is presented. Different gas sensing materials as polyaniline (PANI), Teflon AF 2400, polyisobutylene (PIB), polyepichlorohydrin (PECH) are considered. They are chosen according to the type of gas to be detected and the desired accuracy: Teflon AF 2400 thin film for the detection of CO₂, PANI nanocomposites film that belongs to the group of conductive polymers for the detection of CO, NO₂ and phosgene (COCl₂), and PECH and PIB for the detection of dichloromethane (CH₂Cl₂, DCM). In the analysis, the simple and useful method of the complete analyses of gas chemical sensors is used. The method is based on the electrical equivalent circuit of the surface acoustic wave sensor. The method is very efficient and can be used for the optimal design of CO₂ sensors. The results are compared with those presented in public literature and good agreement is obtained, demonstrating the validity of modelling. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of Water Vapor on the Response of Mg-Doped SrTio3 Ceramic Oxygen Sensors

Mg-doped SrTio₃ thick film sensors fabricated by screen-printing proved to be very promising for the use as oxygen sensors. A study of the influence of water on the response of these sensors gives an important basis for understanding their behavior in practical applications. The influence of water on the sensor response was measured in the oxygen partial pressure region from air (0.21 bar) to pure N₂ (2.5 × 10^–5)and the temperature range from 600 to 800°C. The relative humidity was varied from 1 to 95% RH. The resistance variation as a function of temperature and the activation energy were evaluated under different dry and wet conditions. The results obtained show that the resistance of these sensors generally decreases with increasing water content in the carrier gas and that the effect of water was strongest at lower temperatures as well as at lower oxygen pressures. To explain this behavior, it is proposed that a partial proton conduction is introduced in the water-containing atmospheres and that this contributes to the total conductivity leading to a reduction of the total resistance. Finally, the measurements also show that the response of these sensors still depends on the oxygen partial pressure according to the standard expression even in the presence of water vapor. Therefore, these sensors can still be used as oxygen sensors in humid atmospheres.     

考虑天然气网影响的电网脆弱线路辨识

脆弱线路辨识是电力系统运行风险控制的重要环节。在电网—天然气网耦合背景下,天然气网的运行状态对电网运行影响深刻,因此提出一种考虑天然气网影响的电网脆弱线路辨识方法。首先,构建电网—天然气网耦合系统优化模型,求解得到系统初始运行状态。在此基础上,基于熵理论,建立线路耦合脆弱度因子,用于反映天然气网气源故障对电网线路脆弱性造成的影响。然后,基于复杂网络理论,建立线路结构脆弱度因子和运行脆弱度因子,从结构性视角和运行状态2个方面揭示电网固有的脆弱性。综合上述脆弱度因子,得到用于辨识电网脆弱线路的综合脆弱度指标。采用网络效能和系统输电效率2个指标反映线路故障对电网的影响,验证所辨识出的脆弱线路。由IEEE 30节点系统和比利时20节点天然气系统组成的电网—天然气网耦合测试系统算例表明,所提方法能够有效地分析天然气网对电网脆弱线路辨识造成的影响。     

Hydrogen‐Gas Detection System and its Functions to Make Each Sensor Wireless

A prototype system for detecting hydrogen‐gas leaks in hydrogen filling stations was fabricated. The prototype is composed of a wireless network with 10 sensor nodes for monitoring the spatial distribution of hydrogen‐gas concentration. To make each sensor node to be driven by a battery, field‐effect transistor (FET) sensors and a microprocessor with low power consumption were used. Additionally, two functions were devised and implemented in the microprocessor in each node: one reduces the power consumption of each sensor node and the other controls the transmission to avoid communication congestion when a gas leak occurs. The use of batteries and wireless communications enables the nodes to be placed at optimal sensing locations without regard to the wiring needed with existing gas sensors. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

陶瓷膜法的烟气水分及余热回收中试研究

为研究陶瓷膜在火电厂烟气水分及余热回收应用中的动态性能,在河北某330 MW燃煤电站采用40根微滤膜制作陶瓷膜组件,搭建中试装置,研究烟气流量和冷却水入口温度对水分和热量回收性能、潜热和显热释放情况的影响规律。研究结果表明,烟气流量为9 715 m³/h、冷却水入口温度为18.7 ℃时,膜组件的回收水量和热量分别可以达到43.65 kg/(m²·h)和106.31 MJ/(m²·h)。膜组件在真实的工业生产环境中展现出了良好的回收性能和极好的工业化应用潜力。     

Development of Fiber-Optic Voltage Sensors and Magnetic-Field Sensors

The principle, temperature characteristics, and frequency characteristics of fiber-optic voltage sensors and magnetic field sensors are reported, along with the results of an aging test on these sensors. The fiber-optic voltage sensor utilizes the "Pockels" effect of Bi12SiO20 single crystal and the fiber-optic magnetic-field sensor utilizes the "Faraday" effect of ZnSe polycrystal and Bi12SiO20 single crystal. The basic performance of these sensors has been investigated from the perspective of their use as parts in electrical apparatuses. In addition, in this paper some practical applications in electrical substations and transmission lines are presented. These include a fault section detecting system for gas insulated transmission line (GIL), an optical voltage transformer and optical current transformer which are embedded in gas insulated switchgear (GIS), and a surge voltage receiving system.     

Design of intravascular fiber optic blood gas sensors

Arterial blood gas analysis is one of the most frequently requested tests performed on critically ill patients in both the operating room and intensive care unit. Fiber optic sensors are advantageous in that they require no electrical connection to the patient (except to measure temperature) and are low cost and disposable. The author details the design requirements of fiber optic sensors for continuous monitoring of blood gases and pH, and describes some of the design approaches used to meet these requirements. Attention is also focused on the challenges of using these sensors in human clinical applications