Modified Function Transformation Method for Linearizing Thermistor Characteristics

A mathematical method called Modifled Function Transformation Method(MFTM) for linearizing thermistors is proposed.Theoretically,the method has unified many schemes of linearizing thermistors into a mathematical rational frame,and explained the reason of different circuits having the same capabilities for linearizing the thermistor characteristics.

Characteristics of a Type of NTC Thermistors for Cryogenic Applications

A new type of miniature negative temperature coefficient (NTC) thermistors has been developed and manufactured with Mn-Ni-Cu-Fe oxides. The prepared NTC thermistors were calibrated in the temperature range from 77 K to 300 K with 1 μA exciting currents. The automatic calibration apparatus as well as thermometric characteristics, stability, calibration equations and interchangeability of the manufactured thermistors were investigated. A mean fit equation was obtained: 1/T = 8.60 × 10−4 + 6.54 × 10−4 ln(R/Rref) + 2.46 × 10−5 ln(R/Rref)2 + 9.48 × 10−7 ln(R/Rref)3 − 2.16 × 10−8 ln(R/Rref)4. All the prepared NTC thermistors agreed with this fit with an error of 1.5 K. If the greater accuracy is required, a calibration is necessary, and the calibration accuracy is estimated to be ±10 mK.

A novel(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)high-entropy ceramic nanofiber as a negative temperature coefficient thermistor

The electrical properties of high-entropy ceramics(HECs)have been extensively studied in recent years due to their unique structural characteristics and fascinating functional properties induced by entropy engineering.Novel high-entropy(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)(HE-RECrO_(3))nanofibers were prepared by electro spinning.This work demonstrates that HE-RECrO_(3)nanofibe rs were successfully synthesized at a low temperature(800℃),which is approximately 400℃lower than the temperatures at which chromate ceramics were synthesized via the sol-gel method and the solid-state reaction method.The resistivity of HE-RECrO_(3)nanofibers decreases exponentially with increasing temperature from 25 to600℃.The logarithm of the resistivity is linearly related to the inverse of the temperature,confirming the negative temperature coefficient property of HE-RECrO_(3)nanofibers.The B_(25/50)value of the HERECrO_(3)nanofibers reaches 4072 K.In conclusion,HE-RECrO_(3)nanofibers are expected to be potential candidates for negative-temperature-coefficient(NTC)thermistors.

基于开通延迟时间的MOSFET结温的在线测量方法研究

随着工业需求的发展,对功率晶体管的可靠性提出了更高的要求。器件结温的实时测量因能够起到保证器件正常工作的作用而至关重要。通过对开通延迟时间在线测量方法的研究,设计测量电路测量不同结温下的开通延迟时间,建立二者关系;测量实际工况下的开通延迟时间,反推出器件结温,实现器件结温的在线测量。与红外测温枪测量结果进行对比,结果相近。所提基于开通延迟时间的MOSFET结温的在线测量方法,为今后结温的在线测量提供了新思路。

自动化温度阻值关系校准系统设计及优化

本文针对Pt100和热敏电阻在温度和温升测量中自动化程度低、耗时长、精度不足的问题,研究了Pt100阻值-温度关系和热敏电阻阻值变化量-温升关系,制定了一套温度校准方法,并设计搭建了温度校准系统。同时,结合校准方法与校准需求,开发了自动校准与数据处理程序。结果表明:该系统可实现全自动运行,提高了校准效率与精度,满足温度计高精度校准需求,提供了一种多类型、多温度点交叉校准的全自动控制校准方案。

船载微型Ga-In共晶固定点的现场复现方法研究

将温标固定点技术应用于船载现场是实现温度量值扁平化,提升海洋温度测量水平的重要手段。为了弥补ITS90温标在海洋温区(-5~35℃)范围内固定点数目不足,不能对NTC热敏电阻进行有效校准的缺陷,研制了微型Ga-In共晶固定点,开展了船载控温箱微型Ga-In固定点温坪复现研究,同时探索了环境温度条件下微型Ga-In共晶固定点的复现。采用切线交点法和三次多项式拟合法对微型Ga-In固定点进行了评估和分析。结果表明:微型Ga-In共晶固定点重复性优于1 mK;微型Ga-In共晶固定点应该在固态并低于熔点的环境下保存。采用切线交点法赋值得到微型Ga-In共晶固定点相变温度为15.6549℃,扩展不确定度为1.54 mK(k=2)。

半导体桥火工品的防静电与防射频设计

为提高半导体桥(SCB)火工品的防静电与防射频的双防能力,将静电加固器件瞬态电压抑制(TVS)二极管和射频加固器件负温度系数(NTC)热敏电阻同时集成入SCB火工品的结构中,并研究了上述组合器件对SCB火工品发火性能和抗电磁性能的影响规律。结果表明:集成防护器件后,SCB火工品的安全电流从1.2 A升至1.5 A;抗静电性能满足500 pF/500Ω/25 kV条件下不发火;在22μF/16 V的电容发火条件下,集成SCB火工品的平均爆发时间较SCB火工品增加了1.77μs。因此,该组合型防护器件可以在不改变SCB发火性能的基础上有效提高SCB的抗静电和抗射频的能力。

利用补偿电路设计并制作热敏电阻温度计——温度计设计的一种新思路

利用NTC型热敏电阻,采用补偿法思想(补偿电路)设计了热敏电阻温度计,并进行测温验证了设计效果.补偿法设计温度计是一种完全区别于电桥法的温度计设计新思路,原理简单,实验设备要求低,可设计性强,特别适合于开发成新的设计性实验.

Enhanced time response and temperature sensing behavior of thermistor using Zn-doped CaTiO_3 nanoparticles

In the present study, Zn-doped CaTiO_3 nanocrystalline was synthesized to study the thermistor behavior with temperature. The X-ray powder diffraction analysis showed the formation of a single-phase orthorhombic structure at room temperature. The electrical resistance of the Zn-doped CaTiO_3 increased with increasing doping concentration and decreased at higher measuring temperature, showing a negative temperature coefficient of resistance(NTCR) behavior. Different thermistor parameters were calculated using Steinhart–Hart equations, whilst time domain analysis confirmed faster response towards applied voltage.

CaTiO_(3) nano ceramic for NTCR thermistor based sensor application

It is possible to fabricate highly sensitive NTCR(negative temperature coefficient of resistance)thermistor using nano crystalline CaTiO_(3) synthesized by high energy ball milling.Disc shaped green pellets were prepared and effects of sintering on the disc pellets were studied as thermistor by sintering the samples at 1000℃,1100℃and 1200℃.The as-prepared samples were characterized by X-ray diffraction(XRD),impedance analysis and electrical measurement.The resistivity of the prepared samples varies predictably with temperature:this makes them promising material for temperature sensor.The experimental results prove that nano crystalline CaTiO_(3) ceramic is one kind of thermistor with exponential negative temperature coefficient of resistance in the temperature range of 300-500℃.The samples have the advantages of rapid response,high sensitivity and capability to withstand thermal surges over the temperature range of 300-500℃.Resistance-temperature characteristics are described by thermistor equation with thermistor constant around 4003 K to 10795 K and thermal coefficient of resistanceαaround-1%/℃to-13%/℃.The activation energy is in the range of 0.34-0.93 eV.The observed thermistor parameters are found to be comparable with many of the known thermistor materials.This suggests that the electrical properties can be adjusted to desirable values by controlling the temperature parameter.The influence of fabrication process of disc thermistor and electrical properties are discussed.The study shows the potential of nano crystalline CaTiO_(3) to act as an NTCR material for thermistor applications.

Fabrication of nano-grained negative temperature coefficient thermistors with high electrical stability

Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.

NUMERICAL ANALYSIS OF NONSTATIONARY THERMISTOR PROBLEM

The thermistor problem is a coupled system of nonlinear PDEs which consists of the heat equation with the Joule heating as a source, and the current conservation equation with temperature dependent electrical conductivity. In this paper we make a numerical analysis of the nonsteady thermistor problem. L(infinity)(OMEGA), W1,infinity(OMEGA) stability and error bounds for a piecewise linear finite element approximation are given.

一种基于STM8控制的LED楼道灯设计

楼道灯作为民用建筑常用设备,在楼道灯的设计中利用单片机可以增加其功能。为增加楼道灯的功能、增强其实用性,提出了一种雷达感应楼道灯的设计。首先在电路设计中,针对485通信电气干扰,利用光耦器等多种隔离器进行隔离;其次,利用温度系数B值法和均值滤波函数等方法,表现热敏电阻RT特性,实现模拟信号和数字信号间的转换。仿真结果表明:雷达感应楼道灯有较高的光效,同时其查询模式可以方便设备检修,提高设备维修效率。

Ba/Fe双掺LaCoO_(3)热敏陶瓷材料低温离子传输机制研究

为了开发电学性能优异的深低温材料,采用传统高温固态法制备了Ba/Fe双掺杂的LaCoO_(3)负温度系数热敏陶瓷材料,结合XRD、SEM、XPS等测试手段,研究了材料的物相结构、微观形貌、离子价态分布等,并在22—80 K和80—290 K范围内进行了低温电学性能测试。结果表明:双掺杂改性降低了LaCoO_(3)材料的应用温区,ρ(22 K)在1.85×10^(5)—6.94×10^(6)Ω·cm范围内变化,材料常数B(22—100 K)在146.09—162.75 K范围内变化;在深低温环境下,材料的导电机理由80 K以上时的小极化子跳跃导电转变为80 K以下时的双交换导电,导致了材料常数B发生突变。由此证明,该双掺杂热敏陶瓷材料在极低温测试中具有可开发的应用潜力。

宽温区热敏电阻温度传感器调理电路

目前热敏电阻温度传感器电路一般采用电阻分压电路,非线性补偿温度范围一般在正温区10~100℃,非线性误差为0.5%;一些特殊应用场合要求热敏电阻测量范围在-45~+125℃。针对热敏电阻温度传感器使用温度范围越宽线性误差越大的问题,提出了一种宽温区热敏电阻温度传感器调理电路,采用精密恒流源激励,减小了热敏电阻温度传感器的自热问题,采用集成对数放大器与集成模拟乘法器进行线性化处理,调理电路具有非线性调节、零位调整、满量程调整3个功能,能够给出精确的标准电压0.1~4.9V信号,对每只热敏电阻温度传感器进行温度标定,根据标定数据进行最小二乘拟合,取得了良好的非线性和精度指标。实验结果表明:测温范围为-45~+125℃,非线性达到0.3%以下,测量误差达到±0.3℃。

高居里温度BaTiO_(3)基无铅热敏陶瓷的研究进展

钛酸钡(BaTiO_(3))基正温度系数电阻(PTCR)陶瓷材料由于具有独特的电阻-温度特性,被广泛用于制作各种热敏电阻器件。随着电子材料及元器件无铅化的要求日益迫切,高居里温度BaTiO_(3)基PTCR陶瓷的无铅化是必然发展趋势。介绍了PTCR效应的物理机制、BaTiO_(3)基PTCR陶瓷材料的性能指标及其影响因素,综述了高居里温度无铅BaTiO_(3)基PTCR陶瓷材料的研究进展,讨论了提高无铅BaTiO_(3)基PTCR陶瓷材料性能的策略与途径,以促进这一领域的进一步发展。

热敏电阻在STM32实验教学中的应用

为了减小热敏电阻在测量温度时的测量误差,本文通过测量热敏电阻的电阻值、设计硬件电路、选择数学模型等,实现了温度测量。实验结果表明,通过构建测量电路、选择R-T数学模型,提高了使用热敏电阻测量温度的精度,温度误差降低至0.175 K。本次温度测量实验采用小组形式开展,学生不仅掌握了温度采集的开发流程,还培养了创新思维、动手能力和团队协作能力,达到增强学习自信心,了解真实工业生产过程的目的。

PTC Effect and Its Mechanism in a Novel Thermistor Material —— Hot-pressed SiC/SiO_2 Multiphase Ceramic

As functional materials, PTC thermistor ceramics characterized by a drastic increase in resistivity at its transition temperature have been widely used in high-technology areas such as temperature measurement and indication, temperature control, protective switches and so on. At present, the PTC thermistors are fabricated by means of doping BaTiO3 and their PTC effects result from the existence of acceptor state or electronic trap on grain boundary. But the fabrication process

基于随机森林算法的温度校准方法研究

基于热敏电阻NTC在生产过程、储存条件等客观因素的影响下会造成测量精度较低、准确性较低的情况,且传统校准方法受到热敏电阻非线性温度特性的影响,无法满足高精度和高准确性的校准需求,本文提出引进机器学习中的随机森林算法模型,在0~120℃的温度范围实验条件下,将测试数据分为训练集与测试集,有效验证了随机森林模型适用于NTC的温度校准,通过对模型的修改及优化参数,使温度校准精度达到-0.015~0.020℃。