Dielectric Properties of Capacitive-Type Humidity Sensor Made under Different Pressures

Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative humidity range of 10%～98%,indicating high humidity sensitivity of the sensors.At a certain measuring frequency,the capacitance of the sensors increases as increasing of the preparation pressure,while the sensitivity of the sensors basically remains the same.The frequencies corresponding to the peaks of the dielectric loss of the sensors move to the higher frequency direction as increasing of the relative humidity.At a certain humidity,the frequencies corresponding to the peaks of the dielectric loss move to the higher frequency direction as increasing of the preparation pressure.

Chain-type wireless sensor network node scheduling strategy

In order to reduce power consumption of sensor nodes and extend network survival time in the wireless sensor network （WSN）, sensor nodes are scheduled in an active or dormant mode. A chain-type WSN is fundamental y different from other types of WSNs, in which the sensor nodes are deployed along elongated geographic areas and form a chain-type network topo-logy structure. This paper investigates the node scheduling prob-lem in the chain-type WSN. Firstly, a node dormant scheduling mode is analyzed theoretical y from geographic coverage, and then three neighboring nodes scheduling criteria are proposed. Sec-ondly, a hybrid coverage scheduling algorithm and dead areas are presented. Final y, node scheduling in mine tunnel WSN with uniform deployment （UD）, non-uniform deployment （NUD） and op-timal distribution point spacing （ODS） is simulated. The results show that the node scheduling with UD and NUD, especial y NUD, can effectively extend the network survival time. Therefore, a strat-egy of adding a few mobile nodes which activate the network in dead areas is proposed, which can further extend the network survival time by balancing the energy consumption of nodes.

Multi-type sensor placement and response reconstruction for building structures: Experimental investigations

Estimation of lateral displacement and acceleration responses is essential to assess safety and serviceability of high-rise buildings under dynamic loadings including earthquake excitations. However, the measurement information from the limited number of sensors installed in a building structure is often insufficient for the complete structural performance assessment. An integrated multi-type sensor placement and response reconstruction method has thus been proposed by the authors to tackle this problem. To validate the feasibility and effectiveness of the proposed method, an experimental investigation using a cantilever beam with multi-type sensors is performed and reported in this paper. The experimental setup is first introduced. The finite element modelling and model updating of the cantilever beam are then performed. The optimal sensor placement for the best response reconstruction is determined by the proposed method based on the updated FE model of the beam. After the sensors are installed on the physical cantilever beam, a number of experiments are carried out. The responses at key locations are reconstructed and compared with the measured ones. The reconstructed responses achieve a good match with the measured ones, manifesting the feasibility and effectiveness of the proposed method. Besides, the proposed method is also examined for the cases of different excitations and unknown excitation, and the results prove the proposed method to be robust and effective. The superiority of the optimized sensor placement scheme is finally demonstrated through comparison with two other different sensor placement schemes： the accelerometer-only scheme and non-optimal sensor placement scheme. The proposed method can be applied to high-rise buildings for seismic performance assessment.

A study of transition from n-to p-type based on hexagonal WO3 nanorods sensor

Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 ℃-250 ℃. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 ℃, whereas, it behaves as a p-type semiconductor below 50 ℃. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.

Type-2 Fuzzy Extended Kalman Filter for Dynamic Security Monitoring Based on Novel Sensor Fusion

In this paper, we have focused on several relevant sensors [Laser (for speed measurements), Sonar (for space scanning) and RF (for access rights)] to cooperate in monitoring the security status of multiple dynamic agent in surveillance area. Such coordination is achieved by employing novel concepts of sensors similarity and complementarity. Furthermore, this system is aided with Extended Kalman Filter (EKF) in order to estimate the agent’s non-linear movement. Finally, transforms system state to be able to make a security suspiciousness decision by using type-2 fuzzy logic system to handle uncertainty. It is shown that the system performance can exhibit promising improvements for this dynamic security monitoring application.

GdVO_(4)的氨气敏感性能及高温失活机理

以水热法制备的钒酸钆(GdVO_(4))作为NH_(3)传感器的敏感电极材料原料,通过添加不同含量的钇稳定氧化锆(YSZ)粉末制备了氨气(NH_(3))传感器敏感电极浆料。以YSZ作为固体电解质,添加不同含量YSZ的GdVO_(4)作为敏感电极制备了分步成型的电流型NH_(3)传感器芯片,在700℃下测试了传感器的响应性能。采用X射线衍射(XRD)和场发射电子显微镜(FESEM)对敏感电极材料进行了表征,结合敏感电极粉末高温烧结试验,确定了敏感电极材料高温失活的原因。

Optical Fiber Grating Sensor for Force Measurement of Anchor Cable

The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed in the laboratory - optical fiber grating sensor for force measurement of anchor cable （OFBFMAC）. No similar report about this kind of sensor has been found up to now in China and other countries. This sensor is proved to be an effective way of monitoring in processes of anchor cable installation, cable cutting, cable force regulation, etc, with the accurate and repeatable measuring results. Its successful application in the tie bar cable force safety monitoring for Wuhan Qingchuan bridge is a new exploration of optical fiber grating sensing technology in bridge tie bar monitoring system.

Development of capacitive sensor signal conditioning system for angular displacement measurement using timer IC LM555 and UFDC

In this research paper,we have presented variable area type capacitive sensor signal conditioning system for angular displacement measurement and for this purpose we have used timer LM555 based astable multivibrator and universal frequency to digital converter (UFDC). Due to variation in angular displacement in the variable area type capacitor which is connected in the timer based astable circuit,capacitance changes which in turn changes the time period of the timer circuit output. The time period of the timer output waveform is linear with the capacitance and hence linear with angular displacement. The timer output is further processed with UFDC for the measurement. The experimental results show that the time period is linear with the angular displacement in the range of 0- 180° and the uncertainty we should associate it with this average time period value is the standard deviation of the mean,often called the standard error (SE),which is ± 0.023 μs. Because of the simplicity,this measurement system can be used in both electronic and industrial instrumentation.

不断轨称重衡称重误差机理分析及误差补偿方法改进

针对轨道衡称重误差补偿不佳问题,提出不断轨称量轨式动态衡原理及轨道衡称重误差补偿方法。分析剪力称重波形图,确定传感器非线性特性,结合梯度训练法回归方程,构建误差补偿模型。计算轨道衡在稳定与倾斜状态下的受力,构造传感器输入输出拟合函数,进行误差逼近补偿。实验结果显示,补偿后误差最大减12.13 kg,倾角0°~35°内波动值控于0.7 kg以下,有效提升了补偿效果。

Flexible Impact Force Sensor

When human body is punched by boxing glove, both body surface and boxing glove deform in a complex shape. The purpose of this study is to develop a flexible sensor that can be used in such interface. Firstly, several mechanical phenomena, which are the cause of the error signal of the sensor, are discussed. These are the influences of out-of-plane bending deformation, shear force caused by rubbing, shear force caused by the Poisson’s effect of contact material, and the lateral compressive force caused by the overhanging deformation of flexible material. Then, a prototype sensor that can eliminate the error factors of these is developed. The sensor is a distribution type impact sensor in which sixteen sensor elements are arranged in a 4 × 4 matrix. Punching experiments using a boxing glove are carried out by installing the sensor on the load cell, on the concrete wall and on the sandbag. From the experiment, it is found that the impact force can be measured with good accuracy by using the sensor. Despite the fact that the sensor has inadequate distribution number of sensor elements, the sensor structure meets mechanical requirements for the flexible impact sensor.

Refractometric Fiber Optic Sensor for Detecting Salinity of Water

Salinity is an important property of industrial and natural waters. It is defined as the measure of the mass of dissolved salts in a given mass of solution. High salinity has an impact on people and industries reliant on water. High levels of salt can reduce crop yields, limit the choice of crops that can be grown and, at higher concentrations over long periods, can kill trees and make the land unsuitable for agricultural purposes. Salinity increases the “hardness” of water, which can mean more soap and detergents have to be used or water softeners installed and maintained. This can also cause scaling in pipes and heaters. The experimental determination of the salt content by drying and weighing presents some difficulties due to the loss of some components. The only reliable way to determine the true or absolute salinity of natural water is to make a complete chemical analysis. However, the method is time consuming and cannot yield the precision necessity for accurate work. Thus to determine salinity, one normally used method involves the measurement of a physical property such as conductivity, density or refractive index. The paper reports the refractometric fiber optic sensor for detection of salinity of water. The mathematical model is developed for detection of the refractive index of liquid and simulated in MATLAB. The fiber optic sensor probe is developed to measure the refractive index of the solution containing different amount of salt dissolved in water i.e. different molar concentrations. Experiments are carried out using the developed probe for these solutions. Experimental results are showing good agreement with the simulated results.

Proposal and Verification of Simultaneous Measurement Method for Three Thermoelectric Properties with Film-Type Thermocouple Probe

A new simultaneous measurement method for the measurement of the three thermoelectric properties with a film-type thermocouple probe was proposed. Seebeck coefficient was measured using the steady-state condi-tion of the differential method. The electrical resistivity was measured us-ing the four-probe method and the thermal diffusivity is measured using the periodic heating method. The effectiveness of the proposed method was verified using constantan as a reference material. After describing the effectiveness of the method, the measurement of three thermoelectric properties of Bi0.3Sb1.7Te3, which is a thermoelectric material, was per-formed.

传感器技术理论与实践教学研究与探讨

探究传感器技术理论和实践教学方法,提高学生传感器系统设计的综合能力。首先在基础传感器理论和实践教学中,通过传感器测量电路的对比教学,以及相同功能不同原理的传感器比较教学,夯实学生的传感器基础知识;其次以自顶向下的系统设计方法,引导学生进行传感器系统的设计与调试,培养他们解决复杂工程问题的能力;另外通过引入最新型传感器以及科研热点,拓宽学生的视野。通过这种从基础到系统,再到科学前沿的教学方式,为学生呈现一个深邃而宽广的传感器世界,使学生不仅学会传感器基础知识,而且学会怎么用,还能思考未来如何创新。

火星探测器进入过程防热层温度测量方法

火星探测器进入过程中的防热层烧蚀温度是防热结构设计和气动热环境辨识的关键参数之一。为了满足防热层温度在轨测量的需求,提出采用柱塞式结构大底分层测温探头和U形结构背罩测温探头,与电缆和多通道温度变换器共同组成温度传感器进行在轨测温的方法。设计内容包括测温探头热电偶元件选取、结构形式和安装方式,以及信号集中放大变换和自动冷端补偿等。开展全量程标定和风洞专项试验验证,证明所设计的温度传感器可以实现1300℃以下烧蚀温度变化全过程测量,测量精度达到0.28%。该温度传感器已在我国首次火星探测任务“天问一号”探测器的着陆巡视器上成功应用,可为进/再入航天器烧蚀温度在轨测量的实施提供借鉴和参考。

基于双螺旋式加热器的柔性MEMS流量传感器

针对传统流量传感器的量程限制,提出了一种基于双螺旋结构加热器的柔性基底微机电系统(MEMS)热式流量传感器。在基底上打出均匀通孔阵列以降低热传导损耗,两对测温电阻对称分布在加热器两侧,以获得较宽量程,在微小流量与大流量下均表现出较高灵敏度。采用基于惠斯通电桥的检测电路实现输出电压的测量,同时保持加热器与环境温度恒定温差200 K,对电阻自热进行补偿。传感器工作温度-100~400℃,量程为0~60 m/s;低流速下灵敏度约为12.75 V/(m·s^(-1)),分辨率可达0.001 mm/s,高流速下灵敏度约为1.4 mV/(m·s^(-1)),功耗低至1.3 mW。

氢气传感器在电解制氧系统中的应用研究

针对电解制氧系统中氢气浓度测量受环境因素影响大、测量准确性低等问题,选取了半导体型、催化燃烧型、热导型三类不同原理的氢气传感器,对其在电解制氧系统中的应用进行了试验验证,并对试验结果进行了讨论,分析了各类氢气传感器的使用局限性。

基于雷达传感器的非接触式睡眠呼吸检测系统设计

为解决当前接触式睡眠呼吸监测系统操作复杂、影响睡眠质量的问题,设计了一种非接触式睡眠呼吸检测系统。硬件系统以STM32G431VBT6单片机为核心,设计了信号调理与采集电路、WiFi通信电路,采用K-LC5雷达传感器采集用户睡眠过程中的呼吸信号。软件系统采用数字滤波算法对雷达传感器采集的胸腔位移信号进行处理,从中提取呼吸信号,并基于能量法进行呼吸暂停判定。测试结果表明,所设计系统能有效检测出睡眠状态下的呼吸状态,呼吸率的测试准确率达到了94.44%以上。

Fabrication of Sm-Based Perovskite-Type Oxide Thin-Films and Gas Sensing Properties to Acetylene

Sm-based perovskite-type oxide (SmMeO3: Me = Cr, Mn, Fe, Co) thin-films could be synthesized by a wet-chemical method using an acetylacetone—Poly(Vinyl Pyrrolidone) (PVP) polymeric precursor method at 750℃. The perovskite-type oxide thin-films were tried to apply an acetylene gas sensor based on AC impedance spectroscopy. Among the oxides tested, SmFeO3 thin-film sensor showed good sensor responses in which the AC impedance at 20 kHz was depending on acetylene gas concentration between 2 ppm and 80 ppm at 400℃.

一种基于S型电磁超材料的高温温度传感器设计

针对目前超材料温度传感器存在的量程小且灵敏度较低的问题,设计了一种碳氮化硅基的S型超材料的高温传感器。通过CST电磁仿真软件对超材料温度传感器进行模拟仿真,在其他结构参数一定的情况下,对金属条的长度、宽度、厚度、条间隙及基板厚度等参数进行了设计与优化,确定了传感器结构的最佳尺寸,同时分析了传感器的谐振频率对温度的影响。结果表明,在28℃~1000℃下平均灵敏度可达5.674 MHz/℃。与之前报道的高温传感器相比,灵敏度提高了5倍,这种高灵敏度温度传感器可为航空发动机、武器装备等系统中的高温测试提供一种技术手段。

低轴间耦合的三维电场传感器

使用正交排列的电容式传感单元的三维电场传感器(Three-dimensional electric field sensor,3D EFS)测量空间电场时,轴间耦合效应会严重影响EFS的测量精度。为此,提出了一种电场屏蔽电极,以降低3D EFS的轴间耦合效应,提高测量精度。首先,利用多物理场仿真软件构建电场分布模型。其次,根据仿真结果建立带屏蔽电极的3D EFS电容式传感单元的屏蔽电极模型。最后,建立任意角度的测试平台,将带有屏蔽电极的3D EFS和无屏蔽电极的3D EFS进行实验对比。结果显示,有屏蔽电极的3D EFS的测量偏差在3.2%以内,比无屏蔽电极的3D EFS的测量偏差减少12%。因此,所设计的基于电场屏蔽结构的3D EFS可以使解耦矩阵更加可靠,有效降低空间电场测量偏差。