高频电容式水分快速测定仪

电容式水分传感器以频率信号作为参变量,由电容探头、高频振荡电路、分频器和金属屏蔽盒构成一体。可以用长电缆线与主机测量系统联接。传感频率信号经主机系统的采保、运算和A／D转换器处理后,由数码显示器直接指示水分值。主机系统设有温度补偿电路,通过调整热敏电阻参数来补偿温度对测量精度的影响。该仪器具有速度快、分辨率高、能排除分布电容和噪音干扰、量程宽、线性度好、应用范围广等特点。     

高频电容工水分快速测定仪

电容式水分传感器以频率信号作为参变量，由电容探头、高频振荡电路、分频器和金属屏蔽盒构成一体。要以用长电缆线与主机测量系统联接。传感频率信号经主机系统的采保、 运算和Ａ／Ｄ转换器处理后，由数码显示器直接批示水分值。主机系统设有温度补偿电路，通过调整热敏电阻参数来补偿温度对测量精度的影响。该仪器具有速度快、分辨率高、能排除分布电容和噪音干扰、量程宽、线性度好、应用范围广等特点。     

多臂井径仪测量准确性影响因素分析

随着科学技术的不断发展,多种机械设备在社会诸多领域中得到了广泛的应用,有效促进了众多领域的发展。多臂井径仪作为一种常见的测量仪器,主要针对的是油气油套管内径的测量。但是多臂井径仪在实际应用过程中,其测量准确性与精度受到诸多因素的影响,造成测量准确性与精度得不到有效的保障。为了保证测量工作人员在使用多臂井径仪时的准确度,首先需要掌握多臂井径仪测量原理,明确在实际操作当中极有可能受到的影响,才能采取针对性的措施,有助于确保测量准确性与精度。本文首先阐述了多臂井径仪测量原理,紧接着深入探讨了多臂井径仪测量准确性影响因素,最后提出了相对应的解决措施,旨在提升多臂井径仪测量准确性。     

井下工具中位移传感器温度补偿方法

为了消除高温环境下井下工具中位移传感器温度漂移对测量精度的影响,提出了一种基于BP神经网络的位移传感器温度补偿方法,由LabVIEW编程语言进行算法实现,设计测试电路、通过非等间距温度采样记录位移传感器在不同温度下的漂移量,由BP神经网络模型进行温度补偿。通过仿真试验验证,该方法将高温环境下位移传感器的输出误差最大值由补偿前的4.5%降低到0.6%以下,有效地提高了位移传感器的测量精度,满足了井下工具的应用需求。     

一种新的压力补偿方法

在一些聚合反应过程中,对温度控制要求很严格,这时对温度测量的精度要求特别高,为了消除温度测量中的滞后,可以采用压力测量补偿温度测量的方法。现在压力补偿一般是按照以下的关系来实施的:     

基于O_3/UV法在线COD检测的气体溶解量估计方法

针对臭氧协同紫外方法 (O_3/UV)检测化学需氧量(COD)时存在溶解性气体影响测量精度的问题,提出了一种COD检测过程中气体溶解量的估计方法,用于对COD检测模型的补偿。采集不同浓度的COD标准水样在消解过程中的测量数据和实验分析数据,基于PLS-LSSVMs建立溶解氧量和溶解二氧化碳量的估计模型,将模型的输出作为COD检测模型的补偿项。实验结果表明,基于PLS-LSSVMs建立的模型比PLS或者LSSVMs单独建立的模型估计精度高。采用溶解气体量估计模型进行补偿后的O_3/UV法检测COD与国标法测量结果相对误差均小于5%。对提高O_3/UV法检测COD精度具有重要意义。     

基于O3/UV法在线COD检测的气体溶解量估计方法

针对臭氧协同紫外方法(O₃/UV)检测化学需氧量(COD)时存在溶解性气体影响测量精度的问题，提出了一种COD检测过程中气体溶解量的估计方法，用于对COD检测模型的补偿。采集不同浓度的COD标准水样在消解过程中的测量数据和实验分析数据，基于PLS-LSSVMs建立溶解氧量和溶解二氧化碳量的估计模型，将模型的输出作为COD检测模型的补偿项。实验结果表明，基于PLS-LSSVMs建立的模型比PLS或者LSSVMs单独建立的模型估计精度高。采用溶解气体量估计模型进行补偿后的O₃/UV法检测COD与国标法测量结果相对误差均小于5%。对提高O₃/UV法检测COD精度具有重要意义。     

液态无水氨流量计量的改进

分析了温度波动对液氨流量计量的影响。介绍了带温度补偿的质量流量的测量原理,液氨的密度和温度的数学模型及新测量方法在DCS上的实现。采用带温度补偿的流量计量方法后,提高了计量精度。     

影响涡街流量计测量准确度的几个因素

涡街流量计是生产中测量流量的重要工具之一。文章简述了涡街流量计构测量原理、基本结构,洋细分析了影响涡街流量计测量准确度的选型、安装、温度压力补偿、旋涡发生体迎流面堆积、配管内径与流量计内径不一致等因素,并提出了解决影响测量精度的具体方案。     

集成温度传感器高精度应用研究

通过对集成温度传感器测量原理的深入分析和对其静态特性的实验研究 ,分析了限制其精度的原因 ,并提出了提高精度的解决方案 ,使全量程范围内测量精度可以提高± 0 .5℃。该方案应用于热电偶冷端补偿 ,取得了很好的效果     

ECT系统杂散电容分布研究

对基于FPGA的ECT系统中存在的杂散电容进行分析和研究,其中包括电容传感器杂散电容、高速PCB的工艺杂散和寄生电容、集成电路芯片引脚间与电极引线间的串扰,并提出减小相应杂散的措施。     

Practical method for correcting heterochromatic stray light in dual‐channel spectrographs for colorimetry

Measurements by spectrophotometers more or less suffer from heterochromatic stray light generated in their spectrometers. It is divided into near‐band and off‐band stray lights. While the former appears near the spectral band of the incident flux, the latter distributes broadly across the whole range and is far more problematic from colorimetric point of view. This article presents a practical method for correcting off‐band stray light in dual‐channel array spectrographs often built in modern spectrophotometers. Unlike most correction methods using a line spread function, the presented method estimates the distribution of off‐band stray light across the array as the product of a device‐specific stray light distribution and a total stray light intensity. The latter depends on both the spectral power distribution of an incident flux and a device‐specific rate of change from the incident flux to the off‐band stray light. For further simplification, the method replaces wavelengths by several bands dividing the visible range owing to the moderate spectral dependence of the above rate of change. With those simplifications, the method is practical, effective, and robust enough to work in an inexpensive hand‐held spectrophotometer with the compact spectrograph which often suffers from off‐band stray light. The performance of the method was evaluated with two dual‐channel array spectrographs with and without 2nd‐order‐rejection filter. Specimen lights incident through ten different glass filters were measured and the errors caused by off‐band stray light in the pixel outputs from the array were successfully corrected by the method. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 431–439, 2017     

Measurements of the effects of smoke on active circuits

Smoke has long been recognized as the most common source of fire damage to electrical equipment; however, most failures have been analysed after the fire was out and the smoke vented. The effects caused while the smoke is still in the air have not been explored. Such effects have implications for new digital equipment being installed in nuclear reactors. The US Nuclear Regulatory Commission is sponsoring work to determine the impact of smoke on digital instrumentation and control. As part of this programme, Sandia National Laboratories has tested simple active circuits to determine how smoke affects them. These tests included the study of three possible failure modes on a functional board: (1) circuit bridging, (2) corrosion (metal loss), and (3) induction of stray capacitance. The performance of nine different circuits was measured continuously on bare and conformally coated boards during smoke exposures lasting 1 h each and continued for 24 h after the exposure started. The circuit that was most affected by smoke (100% change in measured values) was the one most sensitive to circuit bridging. Its high impedance (50 MΩ) was shorted during the exposure, but in some cases recovered after the smoke was vented. The other two failure modes, corrosion and induced stray capacitance, caused little change in the function of the circuits. The smoke permanently increased resistance, of the circuit tested for corrosion, implying that the contacts were corroded. However, the change was very small (<2%). The stray‐capacitance test circuit showed very little change after a smoke exposure in either the short or long term. The results of the tests suggest that conformal coatings and type of circuit are major considerations when designing digital circuitry to be used in critical control systems. Copyright © 1999 John Wiley & Sons, Ltd.     

埋地天然气管道阴极保护电位遥测系统及其应用

阐述了在上海天然气高压管道上进行电位遥测的活动,介绍了一种基于微功耗技术设计的数据远程遥控和传输系统的结构组成、配置和功能.通过遥测系统对杂散电流干扰下的管地电位测试分析及采取的排流措施.实践表明:该系统对杂散电流的实时监测效果显著,适用于天然气管道杂散电流干扰下的管道电位测量.     

暂态边界电压法在线测试全钒液流电池阻抗

国内首次采用暂态边界电压法在线研究了全钒液流电池（VRB）的特性,建立了由电压源、电阻以及一个电阻与电容并联的3部分串联而成的等效电路模型;研究了电流密度和荷电状态（SOC）对等效电路元件的影响。实验结果表明,极化阻抗随电流密度的增加有轻微下降,在充电初期和放电末期达到最大值。与极化阻抗相比,充、放电过程中的欧姆阻抗最大,是导致电压损失的主要因素,分别为1.905Ω?cm2和 2.139 Ω?cm2,暂态边界电压法是一种简单且有效的表征全钒液流电池性能的新方法。     

High areal capacitance of FeOOH-carbon nanotube negative electrodes for asymmetric supercapacitors

The relatively low capacitance of negative electrodes, as compared to the capacitance of advanced positive electrodes, poses a serious problem, since this limits the development of asymmetric supercapacitor (SC) devices with a large voltage window and enhanced power-energy characteristics. We fabricate negative SC electrodes with a high capacitance that match the capacitance of advanced positive electrodes at similar active mass loadings, as high as 37?mg?cm^?2. Cyclic voltammetry, impedance spectroscopy, galvanostatic charge-discharge data and the power-energy characteristics of the asymmetric SC device exhibit good electrochemical performance for a voltage window of 1.6?V. Our approach involves the development and application of particle extraction through liquid-liquid interface (PELLI) methods, new extraction mechanisms and efficient extractors to synthesize α-FeOOH and β-FeOOH electrode materials. The use of PELLI allows agglomerate-free processing of powders, which facilitates their efficient mixing with multiwalled carbon nanotubes (MWCNT) and allows improved electrolyte access to the particle surface. Experiments to determine the properties of FeOOH-MWCNT composites provided insight into the influence of the electrode material and the structure of extractor molecules on the composite properties. The highest capacitance of 5.86?F?cm^?2 for negative electrodes and low impedance were achieved using α-FeOOH-MWCNT composites and a 16-phosphonohexadecanoic acid (PHDA) extractor. This extractor allows adsorption on particles, not only at the liquid-liquid interface, but also in the bulk aqueous phase and can potentially be used as a capping agent for particle synthesis and as an extractor in the PELLI method.     

地铁隧道盾构管片氯离子传输模型及特性分析

基于混凝土不同深度处的氯离子浓度分布测定试验,采用Matlab数值模拟方法研究了杂散电流对氯离子向地铁隧道盾构管片内传输性能的影响,并引入杂散电流影响系数建立了一种考虑杂散电流作用效应的氯离子扩散系数时变预测模型.结果表明:杂散电流明显加速了氯离子向地铁隧道盾构管片内的扩散,增大了混凝土不同深度处的氯离子含量.杂散电流对氯离子向地铁隧道盾构管片内传输性能的影响与杂散电流强度之间符合指数函数关系.模型计算结果和试验结果吻合良好.     

冰区漆失效原因分析

在建造丹麦冰区船时,新造船下水到进坞间隔仅40 d,船外板就产生了孔蚀。对此孔蚀原因进行分析后认为：该失效为电化学腐蚀失效,是有机涂层屏蔽性能减弱与杂散电流等共同作用的结果。此分析对后续船的冰区漆施工具指导意义。     

Electrical properties of MgO/p-diamond junction fabricated on homoepitaxial single-crystalline diamond

Sufficiently flat and hillock-free insulating homoepitaxial diamond films were successfully grown on high-pressure–high-temperature-synthesized diamond using a 5-kW microwave-plasma chemical-vapor-deposition system with a 20-ppm-nitrogen-included source gas of 4% CH₄ diluted with H₂. Then, layered MgO/boron-doped (p-type) diamond structures were fabricated on the homoepitaxial insulating diamond. Current (I)–voltage (V) characteristics of these device structures showed strong nonlinear behaviors for both current directions, or those for two electrically-parallel, reversed diodes, with conduction limited mainly by sheet resistance of the p-diamond layer in a temperature range from 300 to 600 K. This suggests that the carrier transport occurred through different current passes in the junction region at both biases. Low-frequency capacitances measured were mainly dominated by the depletion capacitance which was influenced by the bias voltage. At relatively high frequencies, however, the total capacitance measured (C) was determined not only by the depletion capacitance but also by the series resistance and the dispersion capacitance. Equivalent circuits of the MgO/p-diamond structure were deduced to explain the measured I–V and C–V results. A possible conduction mechanism is proposed in relation to the electronic structure of the MgO/p-diamond junction.     

Electrical characterisation of MNOS devices on p-type 6H-SiC

Metal–nitride–oxide semiconductor (MNOS), metal–oxide semiconductor (MOS) and metal–nitride semiconductor (MNS) devices have been fabricated on p-type 6H-SiC substrates without epitaxial layers. They have been characterised using high frequency capacitance–voltage (CV), conductance–voltage (GV) and current–voltage (IV) measurements. High frequency CV characteristics of SiC MNOS structures exhibit a capacitance–voltage behaviour that is very similar to high frequency CV characteristics of SiC MOS capacitors. Similar leakage current characteristics compared with p-type 6H-SiC MNS structures have been found for p-type 6H-SiC MNOS devices, but the SiO₂/Si₃N₄ insulator current is lower, particularly for positive electric fields.