Acceleration sensitivity of piezoelectric pressure sensors and the influence on the measurement of explosion pressures

To measure the explosion pressure inside an enclosure, it is common to install a piezoelectric pressure sensor in the enclosure wall. The pressure wave of the internal explosion inevitably leads to vibrations of the enclosure walls. This unwanted but naturally occurring motion is also transmitted to the pressure sensor mounted in the enclosure wall and results in inertial forces affecting the piezoelectric element. During the measurement of the explosion pressure, this affects the output signal of the pressure sensor since an undesired signal due to the acceleration of the pressure sensor is superimposed on the desired pressure signal. This behaviour of the sensor is described as acceleration sensitivity. The level of acceleration sensitivity depends on the type and construction design of the pressure sensor. Even though this sensor behaviour is basically not a new phenomenon, the evaluation of an international comparison between Ex testing laboratories in the field of flameproof enclosures has shown that the consideration of this issue is a major challenge in daily practice concerning the measurement of explosion pressures and is even often completely neglected.This work evaluates the behaviour of various piezoelectric pressure sensors with respect to the influence of acceleration and investigates the specific impact on the explosion pressure measurement in the field of flameproof enclosures. For this purpose, explosions from typically used explosive mixtures such as hydrogen, propane and ethyne in air are examined. These investigations involve simple model enclosures with various specifications as well as a commercially available equipment for hazardous areas. By using blind holes and specially designed adapters, a practical method is applied to be able to detect the effect of acceleration on the sensor signal separately from the pressure signal. For this purpose, both the discrete-time pressure curves and the frequency components are analysed using Fast Fourier Transform. The use of signal filters as a practical and fast approach to address these unwanted signal components is discussed and evaluated.This paper provides guidelines for typical end-users in the field of flameproof enclosures how to handle acceleration of piezoelectric pressure sensors and the influence on the measurement of explosion pressures correctly.     

基于微型惯性传感器的井下人员跟踪定位系统*

为了解决当前煤矿井下使用的WIFI人员定位系统在煤矿井下复杂环境中受到干扰,造成使用精度误差等问题,研究并提出使用微型惯性传感器制作足部轨迹测量传感器,通过惯性轨迹测量算法计算并跟踪井下人员的移动轨迹。使用基于固定阈值的零速检测技术和基于Kalman滤波的零速校正技术估计并校正由于系统长期工作造成的偏移误差。通过实验证明采用微型惯性传感器能够在不依赖于外部传感器的情况下对人员轨迹实现测量跟踪,Kalman滤波的应用能够减少惯性轨迹测量系统造成的长期漂移误差,可避免井下复杂工作环境对定位造成的干扰。     

振动试验中加速度传感器的选择

参与振动试验中振动量值的获得,最直接也是主要的单元之一是加速度传感器。本文将重点对压电式加速度传感器的工作原理及影响其选型的主要因素进行探讨.     

Layer—By—Layer技术构建化学传感器酶电极检测水体中有机磷的研究

基于层层累积自组装法将胆碱氧化酶和胆碱酯酶逐层固定在电极表面,制备了电流型水质有机磷检测化学传感器。讨论了自组装膜层数、pH值、温度对传感器电流响应的影响。制备的化学传感器对有机磷在浓度10^-9～10^-5mol／L呈良好的线性响应,检出限为1×10^-10mol／L。传感器的稳定性好,30天时的响应值仍保持90％。     

用微生物传感器测定BOD的研究

本研究选用性能优良的微生物,采用夹层法制备微生物并解决了其菌体易流失的问题,与氧电极组装成ＢＯＤ传感器。     

传感器在大气环境监测中的应用探讨

介绍了传感器的概念、原理、特点和分类,对近年来用于大气环境监测的二氧化硫、氮氧化物、二氧化碳、氨、甲烷和其他气体传感器的应用与研究进行了阐述,总结了用于大气环境监测的传感器的特点和局限性,展望了传感器在大气环境监测领域的应用与发展前景。     

基于振动传递率的钢框架损伤识别试验研究

提出了基于振动传递率和主元分析相结合的新的损伤识别方法。首先,由结构无损伤时某2个位置的振动传递率样本构成结构的参考总体,以结构损伤状态时相同位置的振动传递率构成待检样本集;其次,把待检样本逐个代入到参考总体中,构成多个原始数据矩阵;然后,对所有原始数据矩阵进行主元分析并构造相应的控制椭圆和T2控制图,以前2阶主元在控制椭圆和T2控制图中的分布来确定结构是否存在损伤;最后,用一钢框架结构试验验证了本文方法的有效性,并引入振动传递率幅值的总体变化来识别结构损伤位置,损伤识别结果显示,此损伤指标能够很好的识别结构单一位置的损伤。     

基于臭氧紫外协同在线检测水体COD的研究

提出了一种基于臭氧协同紫外(O3/UV)在线检测水体化学需氧量(COD)的方法,建立了以臭氧协同紫外的高级氧化体系对水样进行氧化消解,利用多个传感器信息组合来测定水体COD的方法,通过待测水样所消耗臭氧的量来计算出水样的COD.与传统的COD测定方法相比,具有操作简单方便、消解时间短、运行成本低、无需添加任何化学试剂、不会产生二次污染等优点,具有很好的推广应用价值.     

基于Zig Bee技术的压力传感器数据采集系统设计

介绍了一种基于无线传感器网络的高精度压力传感器数据采集系统的设计方法,将无线传感器网络的Zig Bee技术嵌入到系统的上位机和下位机中,实现了系统可在恶劣环境下的无线通信的需求,系统同时扩展了RS-485数字输出接口和4~20 m A模拟输出接口两种形式,增加了系统的适用性。在实际应用中该系统性能稳定可靠,传感器在常温情况下精度达到0.07%。     

Instream sensor results suggest soil–plant processes produce three distinct seasonal patterns of nitrate concentrations in the Ohio River Basin

The Ohio River Basin (ORB) is responsible for 35% of total nitrate loading to the Gulf of Mexico yet controls on nitrate timing require investigation. We used a set of submersible ultraviolet nitrate analyzers located at 13 stations across the ORB to examine nitrate loading and seasonality. Observed nitrate concentrations ranged from 0.3 to 2.8 mg L⁻¹ N in the Ohio River's mainstem. The Ohio River experiences a greater than fivefold increase in annual nitrate load from the upper basin to the river's junction with the Mississippi River (74–415 Gg year⁻¹). The nitrate load increase corresponds with the greater drainage area, a 50% increase in average annual nitrate concentration, and a shift in land cover across the drainage area from 5% cropland in the upper basin to 19% cropland at the Ohio River's junction with the Mississippi River. Time-series decomposition of nitrate concentration and nitrate load showed peaks centered in January and June for 85% of subbasin-year combinations and nitrate lows in summer and fall. Seasonal patterns of the terrestrial system, including winter dormancy, spring planting, and summer and fall growing-harvest seasons, are suggested to control nitrate timing in the Ohio River as opposed to controls by river discharge and internal cycling. The dormant season from December to March carries 51% of the ORB's nitrate load, and nitrate delivery is high across all subbasins analyzed, regardless of land cover. This season is characterized by soil nitrate leaching likely from mineralization of soil organic matter and release of legacy nitrogen. Nitrate experiences fast transit to the river owing to the ORB's mature karst geology in the south and tile drainage in the northwest. The planting season from April to June carries 26% of the ORB's nitrate and is a period of fertilizer delivery from upland corn and soybean agriculture to streams. The harvest season from July to November carries 22% of the ORB's nitrate and is a time of nitrate retention on the landscape. We discuss nutrient management in the ORB including fertilizer efficiency, cover crops, and nitrate retention using constructed measures.