共查询到20条相似文献,搜索用时 62 毫秒
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针对直流逆变电阻焊机焊接电流精确测量的需求,提出基于光纤电流传感技术的焊接电流测量方法。建立了光纤电流传感器闭环检测系统动态模型,通过优化系统的前向增益,提升了传感器响应速度和带宽。仿真和实验结果表明:传感器的上升时间约为4.1 μs,在DC~30kHz范围内幅频特性衰减小于0.3%。基于该动态模型计算传感器对焊接电流纹波分量的响应,仿真结果表明:系统的动态跟踪能力可满足对纹波电流的测量需求。利用等安匝法对光纤电流传感器进行校准,在直流5~50kA范围内,传感器的测量误差优于±0.05%。现场实验结果证明了光纤电流传感器用于直流逆变焊接电流测量及电焊电流测试仪现场校准的可行性。 相似文献
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磁粉探伤机广泛应用于制造加工业的产品检测中,是一种必不可少的无损检测设备,一般具有周向磁化电流和纵向磁化电流两组电流回路。磁化电流的精度是磁粉探伤机进行计量校准时重要的计量指标,是保证磁粉检测质量的主要参数,其准确度等级一般为5级或10级。通过分析磁粉探伤机磁化电流校准时存在的问题和现场校准需求,结合国内外大电流测量技术现状,提出一种基于分流器和霍尔传感器采样的在线磁粉探伤机磁化电流校准装置。通过优化分流器设计和采取合适的霍尔传感器,实现在线磁粉探伤机交直流周向磁化电流和纵向磁化电流校准。同时,可通过集成化设计实现磁化电流工作时间测量功能和基本误差、频率、波形等参数分析功能。最后,对研制的校准装置样机进行交直流周向磁化电流和纵向磁化电流校准试验验证,结果表明磁化电流准确度可达0.5级,完全满足校准规范要求,且其结构精简、校准便捷,有利于实现现场在线校准,可为磁粉探伤机无损探伤质量提升提供更多技术保障。 相似文献
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校准压电加速度计共振频率及阻尼常数的电流冲击法 总被引:1,自引:1,他引:0
本文提出一种校准压电加速度计共振频率及阻尼常数的电流冲击法,它是利用压电传感器为双向传感器这一特点来实现的。此法具有如下优点:以电流为冲击信号,其大小及波形易于控制;可在实际应用条件下进行校准;可用通用示波器观察在δ(t)电流信号冲击下、压电加速度计输出电压信号的整个过渡过程。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献
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