AN APPARATUS FOR MEASURING THERMAL CONDUCTIVITY OF LIQUIDS UNDER HIGH PRESSURE

We have reported a method for measuring the thermal conductivity of liguids un-der high pressure previously [1,2].Such data are necessary for improving thetechnologies such like processing as acidity,pressure cracking,thermal exploitation ofpetroleum,etc. An apparatus has thus been constructed,as shown schematically in Fig.1,tomeasure the thermal conductivity of liquids under pressure up to 25 MPa and temperatureranging from 150 to 250℃.The thermal conductivity cell is cylindrical in from,35mmin length and 25mm in inner diameter.The sample is poured into the cell through the     

NTC热敏电阻的宽范围线性化分析与程序处理

NTC热敏电阻由于价格低廉,工业上经常用于替代热电偶或集成温度传感器进行环境温度测量,在批量生产时降低产品成本,但由于其电阻-温度的非线性极大,在温度的宽范围测量时,进行数据采集及微处理器系统处理可能会带来很大的误差.本文基于对HCS34B502F-E5015热敏电阻型温度传感器的数据分析,得出它在单片机系统中基于低成本考虑、V-F转换的温度测量方法.     

A thyristor- and thermistor-based inrush current limiter for DC-link start-up

Large inrush currents can be harmful to equipment subjected to it and can also disturb other devices through voltage dips. Traditional ways of dealing with large inrush currents include the usage of parasitic elements in the supply, negative temperature coefficient (NTC) resistances and start-up relays. These solutions have several disadvantages among which are a non-negligible standby consumption, using a relay or a compromise between inrush current and load losses using an NTC. This paper proposes a solution which solves these disadvantages. The proposed circuit uses a semi-controlled bridge rectifier requiring a very low standby power consumption and is capable of withstanding grid interruptions. Moreover, it is designed to power on only when the load is not too heavy. This is accomplished by the use of positive temperature coefficient thermistors. The presented solution can be used for DC-link start-up circuits in applications with a power range from several watts up to a few kilowatts and it is particularly suitable for on-board battery chargers designed for electrical vehicles.     

Influence of irradiation conditions on the electrical behavior of polyethylene–carbon black conductive composites

The temperature‐dependent resistivity behavior of carbon black–loaded polyethylene (PE) composites irradiated both at room temperature and 170°C above the PE melting point was studied. The irradiation doses were varied. At a given loading level, irradiation at room temperature corresponded to an energy treatment on a low‐resistive, solid, three‐phase composite system, while at a high temperature it corresponded to a treatment on high‐resistive, viscous, two‐phase system. The irradiation condition had a complicated influence on the electrical response to temperature. The resulting composite structure was analyzed by using differential scanning calorimetry, gel fraction, and wide‐angle X‐ray diffraction. The results were then discussed by comparing them with those of the unirradiated sample. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 494–499, 2000     

风矢量的自动检测

风速,是自然界中的一个很重要的信息,它包括两个参量：速度和风向。本文综合了国内外的不同测量方法,重点介绍了一种智能低耗风传感器。它由两个自热PTC（正温度系数）元件构成,可以在两个方向测出可靠的风矢量。文中还介绍了该传感器的建模方式和检测方法,该方法可以有效地利用校正程序自动补偿由于器件的非线性、元件的被污染及老化等因素造成的误差。     

单片机温度监测系统

介绍了利用单片机对工业环境温度进行实时监测的系统组成、工作原理以及系统中的关键电路.着重阐述了8031单片机与PC机进行数据通信、处理的控制方法,适合于诸多用于温度显示的场合.     

MWNTs/UHMWPE复合材料的导电行为

采用溶液混合、超声波分散的方法,制备了多壁碳纳米管（MWNTs）/超高分子量聚乙烯（UHMWPE）复合材料,并对其电学性能进行了研究。结果表明,该种方法可以使MWNTs比较好地分散于UHMWPE基体中,复合材料均表现出明显的渗流行为;长径比大的L.MWNTs-60100具有较小的渗流阈值,并且具有较小的正温度系数（PT...     

PTC热敏电阻在空分设备DCS系统中的应用

为实现对低温液体泵实行变频器和DCS系统的双重保护,将电机及其后轴承保护元件——PTC热敏电阻的阻值信号转换为干接点信号,接入DCS系统的DI通道。简介PTC热敏电阻的工作原理,介绍信号转换方案,分析热敏继电器的工作原理。     

Complex impedance analysis of (Y2O3 + CeO2)-YCr0.5Mn0.5O3 composite NTC ceramics

Ceramic compositions based on (aY₂O₃ + bCeO₂)-0.4YCr_0.5Mn_0.5O₃ (a + b = 0.6) were prepared by conventional solid state reaction at 1200 °C, and sintered under air atmosphere at 1600 °C. For 0 ≤ a < 0.6, XRD patterns have shown that the major phases presented in the calcined powders are Y₂O₃, CeO₂ and orthorhombic perovskite YCr_0.5Mn_0.5O₃ phase, respectively. SEM and EDAX observations confirm the YCr_0.5Mn_0.5O₃ phases mostly exist at the grain, whereas the Y₂O₃ and CeO₂ phases mainly exist at the grain boundaries. Complex impedance analysis shows that, for 0 < a ≤ 0.6, single semicircular arc whose shape does not show any change with temperature. Nevertheless, for a = 0, two overlapping semicircular arcs are observed at and above 300 °C. The grain boundary properties exhibit thermistor parameters with a negative temperature coefficient characteristic. The relaxation behavior and conduction for the grain boundary could be due to a space-charge relaxation mechanism and oxygen vacancies, respectively.     

矿井风速传感器的设计

矿井风速的监测是保证矿井安全生产的重要因素,矿井的工作条件特殊,工作环境复杂,风速测量在矿井安全中是一项重要内容,介绍了采用负温度系数热敏电阻器为检测元件的风速传感器的测量原理,得出了风速与热敏电阻变化的关系,阐述了风速测量原理。