Low temperature fired positive temperature coefficient resistors

Through the addition of BN as a sintering aid, Y-doped BaTiO₃-based positive temperature coefficient resistors (PTCR) can be fabricated at temperatures below 1200‡C, which is much lower than is required when conventional sintering aids such as silica or A1₂O₃, SiO₂, and TiO₂ (AST) are used. In comparison with the PTCR containing SiO₂, the low-temperature-fired thermistor shows an enhanced PTC effect and a much higher temperature of resistivity maximum. Electrical properties of the BN-added BaTiO₃, (Ba,Sr)TiO₃, and (Ba,Pb)TiO₃ ceramics were discussed.     

Emitter-junction temperature measurement under nonuniform current and temperature distribution

A computer analysis of the temperature dependence of emitter junction voltage under an assumed nonuniform temperature distribution is presented, which demonstrates a temperature averaging effect when using junction voltage as an indicator of junction temperature.     

基于光纤光栅传感器的海水入侵温度测量系统

近年来海水入侵造成各地沿海滩涂出现了大面积生态退化,对滩涂温度的有效测量有利于监控滩涂海水入侵的情况解决生态平衡问题;通过对光纤光栅结构的特殊设计解决了基底热胀冷缩产生的应变对温度的测量,实现了传感器的解耦;光纤光栅传感器的重复性实验和标定实验,结果表明温度传感器的灵敏度在10.21 pm/℃以上,线性度达到了99 %以上,精度为0.2 ℃,分辨率达到0.1 ℃,传感器具有良好的性能;在现场试验中,将3个光纤光栅传感器串联组成2000 m的传感器系统对滩涂的温度进行测量,数据表明该传感器可以在实际温度测量中进行使用。     

温补晶体振荡器的频率温度稳定度

大部分晶体振荡器生产厂家的数据手册不会兼顾所有使用者的需要,特别是温补晶体振荡器的频率温度稳定度指标,多数情况下,数据手册所列指标往往只适应于某一类典型的应用场合或只符合生产厂家与其某几个主要用户的验收规则,所以只有充分理解频率温度稳定度的不同定义方法、与频率温度稳定度相关的其他频率温度特性指标、不同的环境温度测试方法,才能正确制定符合自己使用要求的频率温度稳定度指标,不加分析地简单套用频率温度     

基于反射温度补偿及入射温度补偿的红外测温影响分析

以红外辐射理论及红外热像仪测温原理为基础,为解决环境高温物体对红外测温的影响,提出反射温度补偿和入射温度补偿两种方法。分析了两种温度补偿方法的理论可行性和实际操作方案并具体进行实验测温对比。对4个硫化矿样本分别应用两种补偿方法同未经补偿的红外测温进行实验测温对比研究,分析结果显示:经过温度补偿后,相对误差明显小于未经补偿的红外测温,且反射温度补偿法较入射温度补偿法更为精确,验证了两种温度补偿方法的可用性及精确性。两种补偿方法在保证测量精度的同时拓宽了普通红外热像仪的应用范围,保证了硫化矿自燃红外预测数值精度。     

Brightness temperature emitted by layered media with nonuniform temperature profile

Based on the transmission-line theory, this paper describes a new procedure to calculate the radiation from layered media with nonuniform temperature profile. The result is compared with those obtained through the incoherent method and the analysis of the electromagnetic fields.     

红外高温温度场中非完全温度点重建方法与预测精度的研究

在高温温度场重建过程中,仍然需要通过温度场的单点温度值来构建整个温度场的温度分布情况。以焊接温度场为例,通过反距离加权法、克里格法和样条函数法三种插值方法,分别对其空间变异和布局进行了分析和重建。结果表明:不同插值方法对预测精度影响不显著,而采样点数量则显著影响了温度场空间分布的重建精度。在温度场重建过程中,25个采样点进行重建是比较适宜的采样数量。将得出的结论与最佳采样公式进行比较,发现使用公式计算的最佳采样数量相对偏低,说明不考虑采样点实际的空间变异情况,仅使用最佳公式得到的采样数量进行温度场的重建会导致重建结果的不准确。     

液氮温区集成式数字温度传感器设计

温度传感器是制冷型红外焦平面探测器的重要组成部分,它用于测量探测器工作温度,其输出用于制冷机控制,从而控制探测器温度。探测器的工作温度将直接影响探测器的性能,如信噪比、探测率和盲元率等。针对传统PN结温度传感器需要模拟信号处理电路及易受电磁干扰的弊端,设计了一种基于CMOS工艺的集成式数字温度传感器,可以集成到红外焦平面探测器读出电路中,直接通过SPI接口输出数字测温值。设计的集成式数字温度传感器采用0.35 m CMOS工艺流片,芯片面积为380 m500 m（不包含PAD）,在电源电压2.5 V和采样频率6.1次/s条件下,功耗为300 W,分辨率0.061 6 K。在77 K温度下输出的RMS噪声为0.148 K。测试结果表明,集成式数字温度传感器可以应用于制冷型红外焦平面探测器温度测量。     

恒温流体供应器温度检测和控制的实现

很多工业生产及高档生活要求高精度的恒温流体供应。尤其对于需要传输一定距离的流体温度难以准确控制。本文研究了恒温流体供应器如何对流体温度检测和精确控制的新方法。针对供应器的可靠性,系统采用了流体温度控制监测和供应温度检测相互独立的方法;针对工厂生产效率或人们生活的便利性,采用了模糊控制和细化功率等级的方法实现对流体温度的...     

基于亮度温度模型的多光谱真温反演算法研究

针对传统的非接触式真温反演算法存在反演速度慢和精度低等问题,提出新的基于亮度温度模型的约束真温反演算法(constrained true temperature inversion algorithm,CTTIA)。 在建模过程中,发现发射率和亮度温度存在内在联系:由亮度温度到发射率的普适规律和由发射率到亮度温度的普适规律。通过仿真实验发现当发射率的样本数量巨大时,CTTIA不但可以为实验提供理论指导,还可大大提升发射率样本的选取效率。在1 800 ℃和2 000 ℃两个温度点下建立9个波长通道对被测目标进行测量计算。结果表明,CTTIA与二次测量算法 (second measurement method,SMM) 相比,精度基本相同,反演时间最高节约了82%。说明该方法的研究是非常关键且重要的,是很有研究价值的。     

高温NTC热敏电阻材料的研究进展

高温NTC热敏电阻材料可制备用于汽车电子、军工、航天等领域超宽温区测温的热敏元件。概述了高温NTC热敏电阻材料的研究,主要集中在具有钙钛矿结构的材料体系以及材料的掺杂改性研究上。基于钙钛矿结构热敏材料NTC效应机理的解释大多集中在氧空位迁移模型、电子跃迁模型和渗流理论等方面,提出应用于高温宽温区测温的具有高电阻率低热敏常数特性的NTC热敏材料是高温NTC材料的发展方向。     

Silver-indium joints produced at low temperature for high temperature devices

A two-step fluxless bonding process adopted to produce high temperature silver-indium joints (80 wt% silver and 20 wt% indium) at relatively low process temperature of 206/spl deg/C has been developed. After annealing the joint continuously for 26 h at 145/spl deg/C, its melting temperature increases to 765-780/spl deg/C, as confirmed by a de-bonding test. The technique thus developed provides a viable alternative to packaging many high temperature devices running at 350/spl deg/C and above. The bonding quality of the Ag-In joints produced was examined using scanning acoustic microscopy. The joint cross-section was also studied using a scanning electron microscope equipped with an energy dispersive X-ray (EDX) spectroscope to find the local microstructure and composition. The results have shown that the joint is nearly void-free and uniform in thickness ranging from 7.2 to 7.8 /spl mu/m. The annealed sample joint, as determined by EDX, is mainly composed of AgIn/sub 2/, Ag/sub 2/In, and AuIn/sub 2/ grains embedded in an Ag-rich Ag-In alloy matrix. During joint formation, the intermetallic compound AgIn/sub 2/, in particular, prevents the indium layer from oxidation, and therefore, no flux is needed. In addition, low process temperatures help to reduce the thermal stresses developed in the bonded structure due to thermal expansion mismatch. Finally, reliability tests were conducted on three sets of annealed joints using a high temperature oven running continuously at 500/spl deg/C for 10, 100, and 1000 h each. Scanning acoustic microscopy (SAM) images on these samples confirmed that the joints have an excellent survivability in a high temperature environment.     

Taking body temperature, inside out [body temperature monitoring]

Originally developed in the mid-1980s by NASA for monitoring the body temperatures of astronauts on the Space Shuttle, the "radio pill" has now found a new application in the football field. Several pro and college teams have begun issuing these multivitamin-size pills to players who they think might be at risk for heatstroke. Once swallowed, the pill acts as an internal thermometer, providing continuous readings of a player's body temperature, which can be picked up by a sensor placed against the small of the player's back. The radio pill relies on a temperature-sensitive quartz crystal oscillator whose vibration frequencies are well known for temperatures ranging from -60/spl deg/C to 150/spl deg/C.     

基于K型热电偶温度传感器的测温系统研究

在飞机热交换器健康状态检测采集温度时,对于精确性和便捷无线传输要求的问题,建立一个利用K型热电偶温度传感器进行温度采集的系统。该系统将采集到的数据通过WiFi进行传输,并利用静态校准和数据拟合的方法提高测量精度。系统结合上位机,可实现在远离恶劣的实际工作环境下完成温度的实时采集、保存、分析和历史查询。实验结果表明,该系统不仅成本低、易操作,而且经过静态校准和数据拟合之后,传感器测量精度能够控制在0.5℃以内,可实现较精确的温度采集。     

一个适用于极低温的宽温度范围子电路MOSFET模型

本文描述了一个适用于低温下的MOSFET子电路SPICE模型。其中引入了两个电阻用于描述冻析效应,并开发了这两个电阻的解析的行为模型。该模型在从极低温到常温的较宽的温度范围内均适用。     

基于红外测温技术的轴温探测系统的设计

多年来铁路运输在国家经济建设中一直扮演着重要角色,铁路运输安全也逐渐受到了人们的重视,其中保障车辆运输安全的红外线轴温探测技术是关键,也存在一些不足,诸如抗干扰能力低、可靠性差、故障率高、维护不方便且成本高等。选择了合适的相关器件,结合实际设计了放大及滤波电路,并对轴温调制方式进行了比较分析与改进,最终基本实现了探头系统降噪和轴温采样系统的降噪设计,大大提高了列车运行的安全。