共查询到17条相似文献,搜索用时 62 毫秒
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本文叙述用精密直流光电温度计昨现纯金属铝凝固点的实验装置和实验方法,复现铝凝固点的总不确定度小于50mK,置信度为99%。实验中对3个铝点黑体石墨坩埚容器的凝固温度进行了多次测量,3个容器的铝凝固点温度之差不大于10mK。在8个月的时间内,对同一铝点坩埚容器的铝凝固点温度进行了11次测量,其标准偏差为15mK,长期重复性也很好。 相似文献
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介绍了国际计量局(BIPM)温度咨询委员会(CCT)关键比对4即铝凝固点及银凝固点容器国际比对。采用固定点容器直接比对的形式进行,共11个国家实验室参加了该项比对,介绍了比对的组织、比对过程、实验方法以及参考值的选取,同时给出了比对结果及比对等效图。 相似文献
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钠钾合金热管校准炉利用钠钾合金热管提供均匀、稳定的温场校准温度计。在研究钠钾合金热管校准炉热特性过程中,发现:温控仪PID参数显著影响钠钾合金热管校准炉的性能。因此,寻求合适的PID参数是研究钠钾合金热管校准炉性能的重要环节。在试凑法确定PID参数基础上,通过人工调整参数的方法,确定合适的控制参数。实验结果表明:钠钾合金热管在约200℃和400℃分别运行时,若PID参数不合适,钠钾合金热管校准炉内温度稳定性不理想;优化PID参数后,钠钾合金热管校准炉在7个小时内温度稳定性为±4mK。。 相似文献
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目的:介绍并建立起面制食品中铝的石墨炉原子吸收光谱法。方法:将面制食品试验样品于85℃进行烘烤(4小时),然后经520℃进行灰化(6小时),采用0.5%HN03溶解并定容,采用石墨炉原子吸收光谱法测定铝。结果:测定线性范围为1.0~50μg/L,相对偏差在1.1%~4.3%,回收率为93.6%~98.2%。结论:在面制食品中铝的测定采用石墨炉原子吸收光谱法方便、快捷、准确,结果满意。 相似文献
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复现银凝固点以上国际温标(ITS-90) 总被引:4,自引:0,他引:4
叙述中国计量科学研究院复现我国银凝固点以上国际温标(ITS-90)的原理、方法、仪器设备、实验结果、温标不确定度评定以及参加国际关键比对的初步结果.我国961.78℃~2200℃温度基准的扩展不确定度为0.10~0.65℃(置信水平p=0.99).1998年参加国际计量局温度关键比对,结果令人满意. 相似文献
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W. L. Tew J. R. Labenski S. W. Nam S. P. Benz P. D. Dresselhaus C. J. Burroughs 《International Journal of Thermophysics》2007,28(2):629-645
Johnson noise thermometry (JNT) is a primary method of measuring temperature which can be applied over wide ranges. The National
Institute of Standards and Technology (NIST) is currently using JNT to determine the deviations of the International Temperature
Scale of 1990 (ITS-90) from the thermodynamic temperature in the range of 505–933 K, overlapping the ranges of both acoustic
gas-based and radiation-based thermometry. Advances in digital electronics have now made viable the computationally intensive
and data-volume-intensive processing required for JNT using noise-voltage correlation in the frequency domain. The spectral
noise power, and consequently the thermodynamic temperature T, of a high-temperature JNT probe is determined relative to a known reference spectrum using a switched-input digital noise-voltage
correlator and simple resistance-scaling relationships. Comparison of the JNT results with standard platinum resistance thermometers
calibrated on the ITS-90 gives the deviation of the thermodynamic temperature from the temperature on the ITS-90, T − T
90. Statistical uncertainties under 50 μK·K−1 are achievable in less than 1 day of integration by fitting the effects of transmission-line time constants over bandwidths
of 450 kHz. The methods and results in a 3 K interval near the zinc freezing point (T
90-ZnFP ≡ 692.677 K) are described. Preliminary results show agreement between the JNT-derived temperatures and the ITS-90. 相似文献
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J. R. Labenski W. L. Tew S. P. Benz S. W. Nam P. Dresselhaus 《International Journal of Thermophysics》2008,29(1):1-17
A Johnson-noise thermometer (JNT) has been used with a quantized voltage noise source (QVNS), as a calculable reference to
determine the ratio of temperatures near the Zn freezing point to those near the Sn freezing point. The temperatures are derived
in a series of separate measurements comparing the synthesized noise power from the QVNS with that of Johnson noise from a
known resistance. The synthesized noise power is digitally programed to match the thermal noise powers at both temperatures
and provides the principle means of scaling the temperatures. This produces a relatively flat spectrum for the ratio of spectral
noise densities, which is close to unity in the low-frequency limit. The data are analyzed as relative spectral ratios over
the 4.8 to 450 kHz range averaged over a 3.2 kHz bandwidth. A three-parameter model is used to account for differences in
time constants that are inherently temperature dependent. A drift effect of approximately −6 μK·K−1 per day is observed in the results, and an empirical correction is applied to yield a relative difference in temperature
ratios of −11.5 ± 43 μK·K−1 with respect to the ratio of temperatures assigned on the International Temperature Scale of 1990 (ITS-90). When these noise
thermometry results are combined with results from acoustic gas thermometry at temperatures near the Sn freezing point, a
value of T − T
90 = 7 ± 30 mK for the Zn freezing point is derived. 相似文献