Digital thermometer circuit for silicon diode sensors

Silicon diode thermometers are now available commercially which conform closely to a specified, albeit non-linear characteristic. An inexpensive circuit has been developed which allows temperatures to be measured with a resolution of 0.01 K between 1.5 and 25 K, and 0.1 K between 25 and 375 K, and with an accuracy that in most applications will be limited by the calibration accuracy of the diode used. The design is based on a standard integrating analog to digital converter. A microprocessor is not required; precise linearization is achieved by means of a look-up table held in an EPROM. The circuit includes a simple digital interface for transferring data to a computer.     

Improving the Traceability of Meteorological Measurements at Automatic Weather Stations in Thailand

A joint project between the National Institute of Metrology Thailand (NIMT) and the Thai Meteorology Department (TMD) was established for improving the traceability of meteorology measurements at automatic weather stations (AWSs) in Thailand. The project aimed to improve traceability of air temperature, relative humidity and atmospheric pressure by implementing on-site calibration facilities and developing of new calibration procedures. First, new portable calibration facilities for air temperature, humidity and pressure were set up as working standard of the TMD. A portable humidity calibrator was applied as a uniform and stable source for calibration of thermo-hygrometers. A dew-point hygrometer was employed as reference hygrometer and a platinum resistance thermometer (PRT) traceable to NIMT was used as reference thermometer. The uniformity and stability in both temperature and relative humidity were characterized at NIMT. A transportable pressure calibrator was used for calibration of air pressure sensor. The estimate overall uncertainty of the calibration setup is 0.2 K for air temperature, 1.0 % for relative humidity and 0.2 hPa for atmospheric pressure, respectively. Second, on-site calibration procedures were developed and four AWSs in the central part and the northern of Thailand were chosen as pilot stations for on-site calibration using the new calibration setups and developed calibration procedures. At each station, the calibration was done at the minimum temperature, average temperature and maximum temperature of the year, for air temperature, 20 %, 55 % and 90 % for relative humidity at the average air temperature of that station and at a one-year statistics pressure range for atmospheric pressure at ambient temperature. Additional in-field uncertainty contributions such as the temperature dependence on relative humidity measurement were evaluated and included in the overall uncertainty budget. Preliminary calibration results showed that using a separate PRT probe at these AWSs would be recommended for improving the accuracy of air temperature measurement. In case of relative humidity measurement, the data logger software is needed to be upgraded for achieving higher accuracy of less than 3 %. For atmospheric pressure measurement, a higher accuracy barometer traceable to NIMT could be used to reduce the calibration uncertainty to below 0.2 hPa.     

Calibration of spatially phase-shifted DSPI for measurement of large structures

We present a method for the calibration of a spatially phase-shifted digital speckle pattern interferometer (SPS-DSPI), which was designed and built for the purpose of testing the James Webb space telescope (JWST) optical structures and related technology development structures. The need to measure dynamic deformations of large, diffuse structures to nanometer accuracy at cryogenic temperature is paramount in the characterization of a large diameter space and terrestrial based telescopes. The techniques described herein apply to any situation, in which high accuracy measurement of diffuse structures are required. The calibration of the instrument is done using a single-crystal silicon gauge. The gauge has four islands of different heights that change in a predictable manner as a function of temperature. The SPS-DSPI is used to measure the relative piston between the islands as the temperature of the gauge is changed. The measurement results are then compared with the theoretical changes in the height of the gauge islands. The maximum deviation of the measured rate of change of the relative piston in nm/K from the expected value is 3.3%.     

主动式双波长红外激光测温标定实验研究

基于主动式双波长红外激光的测温方法,可实现对未知发射率表面真实温度的测量.高精度的标定源是保证双波长红外测温系统测温精确性的重要基础,但目前双波长测温领域的研究工作缺乏关于标定实验结果的公开报道.因此,设计搭建了主动式红外激光测温标定源,研究该标定源的稳定性和均匀性,并对双波长激光测温系统进行标定.结果表明:所搭建主动...     

光纤陀螺组件误差标定ARLS算法

捷联惯性导航系统误差参数标定的准确程度对于系统的导航和定位精度具有重要影响.针对常规速率标定法不能辩识陀螺零偏,未充分预热时光纤陀螺的误差标定易受温度变化影响这两个问题,提出了一种用于光纤陀螺捷联惯性导航系统的新标定算法--自适应递推最小二乘法(ARLS).在建立光纤陀螺误差及其补偿模型的基础上,通过大量温度实验研究了自适应遗忘因子的求取方法,详细推导了ARLS算法及其实现思路.最后通过算法仿真和速率试验证明了在器件特性不稳定条件下,ARLS算法能有效辨识陀螺的误差参数及减小温度变化对光纤陀螺误差标定的影响.     

基于波长函数的辐射温度计一点标定法及其精度的理论估计与实验验证

叙述了通过测量辐射温度计波长函数和一个温度点的输出信号,从而得到辐射温度计全量程标定方法估计了各项误差源对温度标定误差的影响,给出了重要结论。进一步以某多波长高温计为例,在黑体炉标定实验基础,进行了一点标定法的验证,结果证明该方法可以得到较高精度的标定。     

The 27 Ω rhodium-iron ceramic sensor

The 27 Ω rhodium-iron ceramic sensor is suitable for the measurement of temperatures from 1.2 to 300 K, and can be used up to 800 K. The sensor has been available for over 30 years, and around 12,000 units have been produced in this period. A new manufacturer of the rhodium-iron wire has resulted in different resistance-temperature behaviour with each wire batch. This has required a re-analysis of the calibration data. We discuss two types of calibration data: multi-point across the temperature range, and three-point at temperatures close to 4.2 K, 77 K, and 273 K. In both types it is shown that a reference function is of help with the data analysis. We propose a method for improving the interpolation accuracy for a three-point calibration when using a reference function.     

无源器件噪声标准值计算方法的研究

对于矢网中噪声选件计量过程所急需的噪声标准值计算方法展开了研究。报告了无源器件噪声标准值的含义和现有计算方法的特点,并通过现有的两种方法和不同温度条件的实验数据,对比分析了噪声标准值与环境温度、无源器件S参数的关系。基于无源器件噪声模型,提出一种包含温度参数的新型矢量计算方法。在290 K环境温度下,该方法与商业化软件计算结果的最大偏差在10^-4~10^-5量级,在297 K环境温度下,噪声系数标准值计算准确度提高了0.08 dB左右,同时实验证明了环境温度对于最佳源反射系数的幅值和相位几乎没有影响。     

低温下微机高精度热电偶温度计标定系统

组建了一套低温下高精度热电偶自动标定系统。该系统结构简单，方便可靠，控温精度为０．０１Ｋ。     

20—80K低温压力传感器校准系统的研制

针对低温压力传感器的精确测量,设计并搭建了一套20-80 K低温压力传感器校准系统,介绍了系统中恒温试验腔的原理、结构及连接方式,验证了恒温试验腔内温度场的均匀分布。恒温试验腔完全浸没在液氢中,通过温度控制系统调节腔内电加热丝功率,来实现对测试环境温度的控制。试验结果表明,该系统结构紧凑,安全可靠性高,性能稳定,测试温区内变温有良好的温度梯度,温控精度在±0.2 K以内,可通过压力标准源对安装在恒温试验腔内的低温压力传感器进行精确校准。     

热敏电阻在液体火箭发动机试验中的应用

阐述了目前应用于低温推进剂液体火箭发动机试验的热敏电阻温度传感器的特点，介绍了热敏电阻温度传感器在液体火箭发动机试验中的应用方案，包括信号变换器设计、传感器校准数据处理方法、传感器自热效应分析以及测量系统组成，分析了影响测量不确定度的因素，给出了应用热敏电阻温度传感器的测量不确定度小于0．3K。     

基于分段线性法的红外辐射计响应度标定研究

基于溯源至国家高温基准的黑体辐射源对SR 5000N型辐射计光谱响应度进行标定。建立了系统响应度标定模型,在373～773K温区进行了响应度标定实验。实验结果表明:在此温区内黑体理论光谱辐射亮度与基于校准的光谱响应度得到的黑体光谱辐射亮度在8～14μm频谱内的相对平均偏差优于1%,具有较好的一致性。     

环境条件对透气度非线性流量盘校准的影响

为了分析环境条件对透气度非线性流量盘的流量测量的影响,分别选取15²0℃之间的12个环境温度值,0.720℃之间的12个环境温度值,0.7¹.1倍标准大气压之间的9个环境压力值,10%1.1倍标准大气压之间的9个环境压力值,10%⁸0%之间的8个环境湿度值,对流量盘进行了一系列的数值模拟研究,并对流场内部流动情况进行分析.数值模拟表明:流量的测量结果对大气压力和环境温度的变化较为敏感,流量随大气压力的升高而降低,随环境温度的升高而增加;空气的相对湿度对流量盘的测量结果影响不大.最后,得到了非线性流量盘使用过程中环境因素与体积流量之间的关系式,验证了模拟方法的准确可行性.     

Blackbody calibration sources of high accuracy for a spaceborne infrared instrument: the Along Track Scanning Radiometer

We describe the two 140-mm-aperture simulated blackbody sources used for the on-board calibration of the Along Track Scanning Radiometer, a spaceborne thermal infrared instrument for the accurate remote sensing of sea surface temperature, in operation since 1991. The design of these spaceborne sources, which operate at ≈ -10 °C and ≈ +30 °C, allows them to meet their unprecedented accuracy goal, namely a 3σ uncertainty in their brightness temperature of <0.1 K for the whole mission. This performance is empirically demonstrated in the laboratory and in flight by long-term temperature readout tests, temperature uniformity measurements, and direct emissivity measurements.     

Evaluation of the energy parameter J on rubber-like materials: Comparison between experimental and numerical results

The general purpose of our study is the determination of the energy parameter J when dealing with fracture of rubber-like materials. The energy parameter J is expressed in a multiplicative form in which a calibration factor is introduced in order to take into account the finite dimensions of the specimen. The parameter J, issued from fracture tests performed on S.E.N.T specimen of an E.P.D.M rubber is compared with the the J integral which is computed using a finite element procedure for the non-linear elastic materials with large deformation. The numerical results are in good agreement with the experimental data when considering the deeply cracked specimen (a/w ≥ 0.5). Below this limit, a divergence is pointed out which is attributed to a lack of accuracy of the identification procedure used to determine the experimental calibration factor. When this one is determined using the numerical J integral results, a better concordance is obtained.     

Quantification of the evaporative cooling in an ethanol spray created by a gasoline direct-injection system measured by multiline NO-LIF gas-temperature imaging

Two-dimensional gas-phase temperature fields were quantitatively measured in an evaporating ethanol spray with multiline excitation thermometry based on laser-induced fluorescence of nitric oxide (NO-LIF). This technique yields absolute temperature fields without calibration and simultaneously detects the spray position. The accuracy of the presented temperature measurements is +/-1 K. Systematic errors of the scanned multiline thermometry approach due to time averaging in turbulent systems were investigated and found to be negligible. The pulsed spray was generated by a gasoline direct-injection nozzle with swirl injecting ethanol into air in a flow cell at room temperature and atmospheric pressure. The gas temperature inside the spray cloud was found to decrease by 10 K at approximately 5-10 ms after injection. Different injection pressures influence the evaporation behavior.     

高精密测温电桥的标定与评估

使用RTU和RBC两种精密仪器对中国计量科学研究院中温基准实验室的F900高精密测温电桥进行了标定和评估,分析了不同工作频率、不同输出电流在长杆标准铂电阻温度计测温范围内对测量精度的影响。结果表明:电桥在不同的工作频率下精度的差异比较明显。工作频率为25 Hz时,使用RTU和RBC进行标定的最大测量偏差分别约为0.01 mK和0.06 mK;工作频率为75 Hz时,使用RTU和RBC进行标定的最大测量偏差约为0.08 mK和0.2 mK,且相比出厂时有了较大的漂移。电桥在不同的输出电流下精度的差异非常小,在15 μK以内。采用RTU及RBC对F900测温电桥评价的结果之间相互印证,该结果对中温固定点基准复现过程的不确定度评定提供了数据支撑。     

大范围二维纳米位移台的控制及非线性校准的实验研究

搭建了基于激光干涉仪测量原理的三轴微位移测量系统,对大范围二维纳米位移台的控制及非线性校准进行实验研究。介绍了双频激光干涉仪测量系统的构成;编写了纳米位移台的控制程序和激光干涉仪数据采集程序;阐述了位移台的非线性校准方法,并通过实验对比了多项式三阶拟合和三阶分段拟合的差别,验证了校准方法的准确性。实验表明:使用三阶分段拟合的校准方法效果更好,校准前,x轴的最大非线性误差为4.052μm,y轴的最大非线性误差为2.927μm;校准后,x轴的最大非线性误差为15nm,y轴的最大非线性误差为17nm,仅为原始非线性误差的1%。     

双目视觉摄像机神经网络标定方法

摄像机标定是精密视觉测量的基础。为了描述双目视觉中三维空间物点坐标和两个摄像机像面像点坐标间的非线性关系,传统的标定方法需要建立复杂的数学模型。而神经网络可以有效地处理非线性映射问题,笔者介绍了一种BP(ErrorBackPropagation)神经网络,并且为了提高网络的学习能力引入了动态因子。用相同的参考数据,将神经网络标定方法与线性标定方法比较,实验结果表明基于神经网络的双目视觉标定方法能获得较高的标定精度。     

基于标准表法的精密数字测温仪校准方法

参考流量与电学计量领域利用标准表对仪器进行校准的方法,提出一种采用高精度的测温电桥与高稳定性的直流电阻箱组合作为标准装置,校准精密数字测温仪的方法.用此方法对精密数字测温仪进行校准并进行测量不确定度分析,结果表明在-195 ～660℃氛围内,温度示值误差的合成标准不确定度为0.5 ～0.7 mK.此方法采用的标准器准确...