在液槽中测试热电偶不均匀性方法探索

介绍了通过测量热电偶在液体槽中250 ℃时的浸没实验特性评价热电偶均匀性的方法。构建的实验装置在液槽上的一个狭小的空间内可产生较大的温度梯度场,热电偶电极通过该梯度场进行扫描得到了在不同位置的热电势值。对一组新制和使用一段时间的铂铑10-铂热电偶进行测试,发现实验数据具有较好的重复性,新制作的热电偶热电势的均匀性明显优于使用一段时间的热电偶。     

铂-钯热电偶高温断裂仿真分析研究

铂-钯热电偶在稳定性和准确度等技术方面优于传统的铂铑10-铂热电偶和铂铑30-铂铑6热电偶,具有广泛的应用前景。但在试验中,发现Pd电极在高温1100℃以上时容易断裂。因此,本文对热电偶点接触结构应力特性进行仿真分析,并设计两种特殊结构形式的铂-钯热电偶。     

标准热电偶自动退火装置

我们温度室的同志,为了更好地开展对二、三等标准铂铑一铂热电偶的检定工作,对标准热电偶的退火工作改做了两项设备,就是标准热电偶在退火橱通电流灼热自动退火装置和退火炉自动控制退火装置。这两项设备的控制系统结构简单,操作方便,能节省人力,提高检定质量。退火橱自动退火装置已经过七年的实际使用,证明性能可靠。     

同名极比较法

同名极比较法是工作用热电偶的一种检定方法。顾名思义同名电极相比较,因此标准热电偶与被检热电偶必须是同分度号才能比对。 将标准热电偶与被检热电偶捆扎成束,并将各测量端牢固地捆扎在一起,使标准与被检热电偶的测量端接触良好.电极之间组成通路。如工作用铂铑10-铂热电偶检定规程中图二所示,(见热电偶检定规程.本文从略)将三支热电偶的测量端牢固捆扎.如同形成一个公共热接点。从理论上讲,任何两种电子密度不同的导体都可以配制成热电偶,那么图中六根热电极中的任何两根热电极都存在着组合热电势。同名极比较法是测定同名极之间的组合…     

0℃～419.527℃温区标准铂铑10-铂热电偶线性内插公式计算方法的实验验证

新修订的《标准铂铑10-铂热电偶》检定规程中对标准热电偶的温度测量范围扩延为0℃～1084. 62℃。本文介绍了多家实验室使用不同实验装置验证标准铂铑10-铂热电偶在0℃～419. 527℃温度范围内可以利用线性内插计算方法。实验结果表明此计算方法得到的结果准确、可靠。     

铂铑10-铂热电偶在1 100～1 300℃外推计算公式的实验验证

介绍了使用辐射温度计在高温黑体炉中来分度铂铑10-铂热电偶,以验证其在1 100～1 300℃范围内的计算方法.实验结果表明,使用现有的400～1 100℃的计算方法外推到1 300℃是可行的.     

用XA热电极丝作铂铑—铂热电偶补偿导线

对于长时间(1000小时)测量燃烧物体的温度(1000—1300℃)采用铂铑—铂热电偶较为合适。鉴于热电偶自由端的长度有限,在400—600℃的温区不得不进行更换,而原有的КПО-П牌号的补偿导线在这一温区不能使用。在这种情况下就可采用在上述温度可靠地工作的XA热电极     

标准热电偶使用中应注意的事项和处理措施

<正>一、影响标准热电偶热电特性和使用寿命的因素1.热电极的氧化和挥发高温条件下,标准热电偶的电极表面被氧化,产生铂和铑的氧化物,这样的氧化物容易挥发,从而使电极成分发生改变,引起热电势漂移。2.杂质含量和分布的影响由于受化学提纯和冶金技术的限制,热电极中存在微量杂质且杂质分布不均匀,通过退火手段,可消除一定杂质,改善杂质分布和热电性能。3.高温下的电极晶粒长大标准热电偶若在超过极限温度环境下长时间使     

调质处理对标准铂铑热电偶热电稳定性的影响

文章主要讨论在实验室制作、使用标准铂铑热电偶中,引起标准铂铑热电偶产生误差的原因以及正确进行调质处理,是提高标准铂铑热电偶热电稳定性的关键.     

熔丝法在钯点分度热电偶的研究

介绍了使用熔丝法在钯点分度热电偶的方法,并对熔丝新形式"小圈法"进行了试验研究.通过实验分析了钯的氧化、钯的纯度以及熔化速度等因素对分度结果的影响.研究结果发现使用"小圈法"分度铂铑热电偶的测量重复性达到0.6 μV,与传统的绑丝法相比有较大的提高;在氧化环境中热电偶钯点分度值比无氧环境下的分度值低1.5 ℃.利用此钯熔丝法装置分度铂铑热电偶的测量不确定度U＝0.8 ℃(k=2).     

Stability Studies of a New Design Au/Pt Thermocouple Without a Strain Relieving Coil

The performance of a simple, new design Au/Pt thermocouple developed by NMIA is assessed. This thermocouple is proposed as a more accurate replacement, over the temperature range from 0 to 1,000°C, for the commonly used Type R and S industrial transfer standards, in a robust form familiar to industrial calibration laboratories. Due to the significantly different thermal expansions of the Au and Pt thermoelements, reported designs of the Au/Pt thermocouple incorporate a strain-relieving coil or bridge at the thermocouple junction. As the strain relieving coil is mechanically delicate, these thermocouples are usually mounted in a protective quartz tube assembly, like a standard platinum resistance thermometer (SPRT). Although providing uncertainties at the mK level, they are more delicate than the commonly used Type R and S thermocouples. A new and simple design of the Au/Pt thermocouple was developed in which the differential thermal expansion between Au and Pt is accommodated in the thermocouple leads, facilitated by a special head design. The resulting thermocouple has the appearance and robustness of the traditional Type R and S thermocouples, while retaining stability better than 10 mK up to 961°C. Three thermocouples of this design were calibrated at fixed points and by comparison to SPRTs in a stirred salt bath. In order to assess possible impurity migration, strain effects, and mechanical robustness, sequences of heat treatment up to a total of 500 h together with over 50 thermal cycles from 900°C to ambient were performed. The effect of these treatments on the calibration was assessed, demonstrating the sensors to be robust and stable to better than 10 mK. The effects on the measured inhomogeneity of the thermocouple were assessed using the NMIA thermocouple scanning bath.     

薄膜热电偶热电特性分析与试验

薄膜热电偶具有体积小、操作简便、准确度高等优点,在精确测温领域显出了极大优势。采用磁控溅射法生产的热电偶在材料组合上几乎是无限的。本文对Ni CrNi Si薄膜热电偶、Ni Cr SiNi Si Mg薄膜热电偶静态下的重复性、使用寿命、温度上限等进行对比、分析,以便在使用中可以更好地"因地制宜"。与大连某高校制作的薄膜热电偶进行对比试验,验证制作工艺对薄膜热电偶性能的重要影响。薄膜热电偶作为一种新型热电偶,在发动机叶片等特殊部件表面测温领域具有广泛的应用前景。     

Thermoelectric Characteristic of High-Temperature Thermocouples W5%RE/W20%RE

In the temperature range (900 to 2800) K, there has been confirmed compliance with the existing national standards for thermocouple wires W5% Re/W20%Re (type A) produced in Russia. The homogeneity within a lot of wires was evaluated by measuring the emf deviations from the corresponding reference function of thermocouples constructed from the front and the rear sections of paired coils of wires. The diameter of the wires amounted to 0.35 mm and 0.5 mm. Stability indicators were thermal emf changes after annealing for 2 hours at 1773 K. It was found that the inhomogeneity of thermoelements did not exceed (4 to 5) K for paired wire coils with a thermoelectric stability within a temperature equivalent of (1.0 to 1.5) K. EMF deviations from the reference table values for the thermocouples investigated did not exceed 1 % in the temperature range of (900 to 2773) K. Such deviations meet the requirements of the new draft of IEC standards 60584-1 and 2. Thermocouples were calibrated in four laboratories by comparison with various standard temperature gauges (type B thermocouple, radiation pyrometer, standard specimens of thermoelements). Measurements were carried out under vacuum, argon, and hydrogen. Depending on the calibration method, the expanded uncertainty of the measurements at 1773 K varied from (2.8 to 8) K.     

Assessment of Temperature Measurements Using Thermocouples at NIS-Egypt

Thermocouples are increasingly used in industry and research. For many industrial heating processes, particularly those carried out at high temperatures, a thermocouple is the most convenient and simple instrument for temperature measurement. In some instances, it is the only feasible method. The aim of this study is to select and recommend the best thermocouples from both base and noble metals to users in industrial and scientific institutions. Different types of thermocouples and calibration methods are described. From this work, the Nicrosil–Nisil thermocouple has been proposed as the best base metal thermocouple and the Au/Pt thermocouple is the most recommended as a substandard up to 1,000 °C.     

基于红外热成像技术的复合式温场测温方法

针对测量目标发射率和吸收率估计不准确将造成红外热像仪测量温场误差较大的问题,提出了用热电偶作为标准建立红外热像仪修正模型的方法.建立热电偶所在位置的修正模型后,用其修正热像仪在其它位置的测量结果,从而提高了热像仪测量温场的准确度.30～200℃的实验证明其修正值具有较好的重复性和复现性.     

Thermocouples with Built-In Self-testing

The aim of this paper is to create a method of built-in self-testing of thermocouples in situ. This aim is achieved by using the equivalent operating time of the thermocouple. The method does not require replacement of thermocouples from their operating place as it could be done during the operation of the thermocouples. The only necessary condition, that makes self-testing possible, is a constant measuring junction temperature during the procedure of self-testing. The determined equivalent operating time allows finding the place of a given thermocouple in the thermocouple’s drift model as well as in the model of thermoelectric inhomogeneity.     

A Critical Look at Type T Thermocouples in Low-Temperature Measurement Applications

Type T thermocouples are commonly used in industrial measurement applications due to their accuracy relative to other thermocouple types, low cost, and the ready availability of measurement equipment. Type T thermocouples are very effective when used in differential measurements, as there is no cold junction compensation necessary for the connections to the measurement equipment. Type T’s published accuracy specifications result in its frequent use in low-temperature applications. An examination of over 250 samples from a number of manufacturers has been completed for this investigation. Samples were compared to a standard platinum resistance thermometer (SPRT) at the LN2 boiling point along with four other standardized measurement points using a characterized ice point reference, low-thermal EMF scanner, and an 8.5 digit multimeter, and the data were compiled and analyzed. The test points were approximately ?196 °C, ?75 °C, 0 °C, + 100 °C, and + 200 °C. These data show an anomaly in the conformance to the reference functions where the reference functions meet at zero. Additionally, in the temperature region between ?100 °C and ?200 °C, a positive offset of up to 5.4 °C exists between the reference function equations published in the United States in ASTM E230-06 for the nitrogen point and the measured response of the actual wire. This paper also examines the historical and technological reasons for this anomaly in the US reference function. The study concludes that Type T thermocouples typically do not conform to the ASTM E230-06 published reference function describing their performance when used to measure temperature in the range of ?100 °C to ?200 °C.     

Preparation and characterization of ceramic thin film thermocouples

Indium tin oxide (ITO), alumina doped zinc oxide (ZnO) and NiCrCoAlY/alumina nanocomposites were systematically investigated as thermoelements. These ceramic thermoelements were initially tested relative to a platinum reference electrode and the resulting thermoelectric properties were evaluated. Bi-ceramic junctions comprised of the most stable and responsive ceramic thermoelements, i.e. those thermoelements with the largest and most stable Seebeck coefficients relative to platinum, were fabricated and tested. A bi-ceramic junction based on nitrogen-doped ITO:oxygen-doped ITO exhibited excellent high temperature stability and reproducibility, however, this thermocouple pair had a relatively low Seebeck coefficient (6 μV/°C). Alumina doped ZnO:ITO thermocouples generated a very large electromotive force at low temperatures but lacked high temperature stability. When nitrogen-doped ITO was combined with a NiCoCrAlY/alumina nanocomposite, a very large and stable Seebeck coefficient (375 μV/°C) was realized. Ceramic thermocouples based on several candidate materials were demonstrated at temperatures up to 1200 °C and the potential of using these materials in other thermoelectric devices including those for energy harvesting is discussed.     

基于高温黑体炉的钨铼热电偶校准方法研究

基于中国计量科学研究院的高温黑体炉设计了一种适用于钨铼偶等高温热电偶的校准方法。优化设计的均温块测温孔轴向均匀性20mm范围内小于0.5℃,优选的测温孔与中心孔的辐射温度差异可达到小于0.5℃。经铂铑10-铂热电偶验证了基于高温黑体炉的校准方法,在800~1300℃与S型热电偶标准热电势间差异小于0.5℃,不确定度评估为0.8~1.5℃,k=2。在800~1900℃范围内,测试了多只不同来源的C型钨铼偶热电势并考核了偶丝校准前后的均匀性,实验结果表明,钨铼偶丝与国际标准钨铼偶热电势的差异基本保持在1%以内,校准不确定度为3.7~13.0℃,相对不确定度为0.7%t (t为温度),k=2。