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1.
针对ADC动态有效位数评价过程中激励正弦信号参数变化对其影响进行了详细深入的实验研究,发现动态有效位数评价误差最小的条件为:正弦信号峰峰值为最小量化阶梯的奇数倍,直流偏移为最小量化阶梯的整数倍,激励信号相位变化对于动态有效位数误差没有明显影响。直流偏移为最小量化阶梯的整数倍加上半个最小量化阶梯时,给动态有效位数造成的误差最大。研究所得结论可用于动态有效位数评价时的正弦信号参量选取实践中。  相似文献   

2.
植物微弱电波信号的时、频域分析   总被引:5,自引:10,他引:5  
在时域和频域上对植物电波信号进行了分析.植物电波信号的幅值处于μV级量级,是一种微弱信号;随时间变化剧烈,在不同时刻的取值关系松散;植物电波信号属于低频信号,其功率谱主要分布在小于5 Hz这一频段.  相似文献   

3.
《中国测试》2017,(10):74-79
医用运动平板参数的准确性直接关系到冠心病诊断的准确性,但目前国内尚无用于医用运动平板心电分析系统溯源的标准信号发生器。为此,通过Matlab得到正弦波、方波和标准心率信号的波形数据,并存入单片机的内部Flash中,采用12位DAC和高频晶振来保证输出信号峰峰值和频率调节的精度,将输出信号经过电压跟随器后通过衰减器进行幅值的衰减以得到微弱信号。实验表明:该标准信号发生器输出的3种微弱信号频率的最大相对误差分别为1.6×10-2%、4.3×10-3%、-3.3×10-3%,峰峰值的最大扩展不确定度分别为0.38%、0.38%、0.54%,均达到设定的技术指标要求,满足医用运动平板心电分析系统的溯源要求。  相似文献   

4.
峰值冲击是轴承故障信号中的重要特征之一,明显的峰值冲击有利于其故障诊断,而低转速工况下轴承故障由于振动能量小,峰值冲击微弱,导致故障特征容易被噪声淹没,通常无法通过包络分析等方法提取。为了增强微弱故障信号中的峰值冲击,提取低转速轴承故障特征,提出了基于Teager峰值能量的故障特征提取方法。采用移动窗口截取原信号,计算截取信号段的峰峰值,从而构造峰峰值特征波形,增强故障信号中的峰值冲击;利用Teager能量算子对峰峰值特征波形进行解调,抑制噪声干扰,提取瞬时冲击成分;根据提取的Teager能量频谱判断轴承的运行状态。实验结果表明,该方法有效提取了低转速轴承的冲击特征,实现了故障的诊断。  相似文献   

5.
由于采集系统的不足对信息造成的损失,使后期的数字信号处理无法补偿的。针对此情况,本文考虑设计一个微弱振动信号自适应采集系统,能够根据被测信号的振幅实时地调节放大器的增益,从而检测出微弱振动信号。  相似文献   

6.
本文提出一种有效提高真空封装硅微陀螺机械稳定性的方法.通过谐振增益与模态频差的参数灵敏度关系可知,随着模态频差的增大,机械谐振增益对模态频差的灵敏度减小,外界环境引起的模态频差的微弱抖动量决定驱动、敏感模态频率差的设计极大值,因此当频差设计值的变化量等于外界引起的频差抖动量且谐振增益满足应用需求时,真空封装硅微陀螺的机械稳定性达到最优.仿真结果表明机械稳定性提高12.7%,最佳封装气压约为5.3kPa.实测结果表明,零漂提高到0.9mV时,刻度因子的线性度为700×10^-6,带宽提高3倍,约为89Hz.该方法为真空封装硅微陀螺仪的参数优化提供了理论依据.  相似文献   

7.
采用四阶Runge-Kutta算法,以信噪比增益和谱功率放大率为随机共振测度指标,研究了电容参数和激励信号均受高斯白噪声扰动时RLC串联谐振电路的随机共振现象。研究表明,欠阻尼RLC串联谐振电路在适当的电路参数、激励信号频率和噪声参数条件下,信噪比增益和谱功率放大率是噪声强度和输入信号频率的非单调函数,且其值均大于1,电路中存在随机共振现象;而在临界阻尼或过阻尼情况下尽管信噪比增益在一定条件下也是噪声强度和输入信号频率的非单调函数,但谱功率放大率取值小于1,电路发生了随机共振现象,改善了信噪比,信号能量却并未得到加强。这一结论使得将欠阻尼RLC串联谐振电路应用于微弱信号检测成为可能。  相似文献   

8.
作为一种重要的信号处理方法,随机共振(SR)能够利用噪声能量增强微弱信号,有效降低噪声信号对特征提取的影响。针对分段对称系统模型随机共振幅值增益不够明显及噪声利用率较低等不足,提出一种分段非线性系统模型。该系统参数独立,易于调节,可通过调节参数诱导最佳随机共振。在双稳态模型下,推导了克莱默斯(Kramers)逃逸率和输出信噪比,同时在模型公式仿真和数值仿真两方面与分段对称系统进行对比分析,用于说明该方法的有效性。结果表明该方法能够有效地提取特征频率,具有良好的放大性能和抗噪声能力。最后将系统应用于不同型号的轴承故障检测,并用自适应智能算法最优化系统参数。结果显示,非对称系统的输出幅值分别为对称系统的8倍,3倍和6倍。数据表明,非对称系统能更有效地实现微弱特征检测与早期故障诊断。该研究进一步对系统在实际工程应用提供了理论指导与依据。  相似文献   

9.
采用前置微电流放大器和可编程增益放大器两级运放,实现电离规离子流的可编程增益放大,以满足在真空度迅速变化且动态范围较宽时对真空度的快速准确测量。介绍了微弱电流信号的放大原理、器件选择原则、单片机控制可编程增益放大器的实现方法、电路抗干扰措施等,并给出了部分测试结果。本文设计的电离规离子流放大电路具有增益动态范围宽、精度高、响应速度快等优点,为托卡马克装置的真空度快速测量系统中离子流测量电路提供了设计参考。  相似文献   

10.
行星齿轮箱振动信号中的故障特征通常淹没在噪声信号中,因此有必要研究如何提取这些微弱故障特征。针对传统奇异值分解特征提取方法中不能自动选择有效奇异值数目的问题,提出了一种基于自适应奇异值分解的行星齿轮箱故障诊断方法。首先根据一定的条件,通过该方法选择几个不同的有效奇异值数目并得到几组不同的重构信号;再根据这些重构信号的偏态绝对值,自动选择最佳的重构信号;最后进行包络分析,得到故障信号的包络谱。仿真和实验对比结果表明,此方法相比于传统的奇异值分解特征提取方法,能够更好地在消除噪声和提取行星齿轮箱振动信号中的微弱故障特征。  相似文献   

11.
三种菊科植物电信号的分析   总被引:2,自引:7,他引:2  
对测得的瓜叶菊(Senecio cruentus)、雏菊(Bellis perennis)和茼蒿(Chrysanthemum coronarium)三种盆栽菊科植物的电信号进行了短时傅立叶变换分析.三种菊科植物的电信号幅值的变化范围分别为-34.07~35.15μV、-94.37~25.03μV和-22.92~21.71μV,能量谱分别主要分布在约0.15 Hz、0.08 Hz和0.11 Hz以下.据此表明三种菊科植物的电信号均为微弱低频信号.另外,还发现三种菊科植物的电信号中于不同时刻出现频率范围不同的“动作电波”成分.  相似文献   

12.
将自制的具有铂金传感器的双重屏蔽微弱电信号测试系统,所获取的植物微弱电信号、小波软阈值消噪、时间序列的求和自回归移动平均(ARIMA)模型等单因素分析耦合成信息融合技术,对雏菊电信号时间序列进行了数据融合分析预测.雏菊电信号为微伏量级,其幅值有随温度的升高而微弱增加的趋势.ARIMA模型对植物微弱电信号特性进行预测是可行的.以节能为目标依据雏菊植物自适应电信号的预测参数可作为建立塑料大棚智能化控制系统的重要依据.  相似文献   

13.
Multiwall carbon nanotube buttressed aluminium 7075 metal matrix composite was synthesized through an amended liquid metallurgy method, which consisted semisolid stirring, ultrasonic treatment and squeeze casting. Aim was to investigate its machinability and surface morphology during electrical discharge machining. Variable machining factors were peak current, pulse-on time and gap voltage, whereas the responses under investigation were electrode wear rate, material removal rate and average surface roughness. Results revealed electrode wear rate, material wear rate and average surface roughness increased on increasing peak current and pulse-on time, but all these responses behaved inversely with the increase of gap voltage. Average surface roughness reduced by around 44 % on reducing the peak current from 10 A to 4 A and increasing gap voltage from 55 V to 80 V at constant pulse-on time of 300 μs; however, it increased by around 25 % on reducing the gap voltage from 80 V to 55 V and increasing the pulse-on time from 100 μs to 300 μs at constant peak current of 10 A. Significance of the process parameters were verified, regression models were developed and morphology of the machined surfaces was studied. Finally, multiple response optimization was conducted following grey relational approach.  相似文献   

14.
Abstract

Acoustic emission (AE) signals generated during the fracture and fatigue of continuous SiC fibre reinforced titanium alloy composites (SCS-6/β21S, SCS-6/Ti–6Al–4V, and SM1240/Ti–6Al–4V) have been measured, and AE parameters have been correlated with microfracture processes. The amplitude distributions of AE signals in both fracture and fatigue were found to have distinct peaks at ~90 dB with reference to 5 μV at the output of the sensor used. These high amplitude AE signals were confirmed to correspond to fibre fracture by direct optical observation, and deduced from sharp crack growth rate excursions measured by an electrical potential difference method. Although the distribution of lower amplitude signals (<70 dB)changed progressively during loading to fracture, it was difficult to distinguish microfracture processes precisely since several potential fracture modes overlap in the amplitude distribution. The ratio of the peak amplitude to the rise time of the AE signals could, however, be classified into several categories, and this method of analysis is most useful in discriminating between fibre/matrix debonding events and fibre sliding events. The present work suggests that the AE technique is useful for damage evaluation in these composites, in general, and in particular it can quantify fibre fracture.

MST/3352  相似文献   

15.
依据菊花(Dendranthema morifolium)植物电信号小波软阈值消噪后的数据,进行了其电信号时间序列的高斯径向基函数(RBF)神经网络预测.菊花植物电信号是一种微弱低频非平稳信号,最大幅值1 093.44μV,最小为-605.35μV,均值-11.94μV;功率谱分布为0-0.2 Hz.该结果说明,利用RBF人工神经网络对植物微弱电信号进行短期预测是可行的,其预测数据可作为以节能为目标依据植物自适应电信号特性建立温室和/或塑料大棚智能自动化控制系统的重要参数.  相似文献   

16.
Microcrystalline silicon films (μc-Si:H) were deposited on stainless steel substrates by bias-assisted hot-wire chemical vapor deposition. The effect of substrate bias and substrate temperature on the crystallinity of μc-Si:H films was studied by Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The results show that both the Raman peak position and the crystalline fraction of the μc-Si:H films deposited at 200 °C were obviously improved by introducing ?800 V substrate bias. The films deposited at 200 °C with ?800 V substrate bias show strongly sharpened Si (111) peak together with Si (220) and Si (311) peaks, which was different from a weak Si (111) peak for those deposited without substrate bias. By increasing the substrate temperature from 200 to 300 °C, while keeping the substrate bias at ?800 V, the crystallinity of the silicon films was further improved, and μc-Si:H films with crystalline fraction of 74 % was obtained.  相似文献   

17.
Zen JM  Lo CW 《Analytical chemistry》1996,68(15):2635-2640
A novel glucose sensor has been contrived by immobilizing glucose oxidase between two nontronite clay coatings on glassy carbon electrode with methyl viologen as mediator. The sandwich configuration proved to be very effective in the determination of glucose. The response of the glucose sensor was determined by measuring cyclic voltammetric peak current values under aerobic solution conditions. The effects of the amount of enzyme immobilized, the operating pH, and the common interferences on the response of the glucose sensor were studied. The detection limit was 5 μM, with a linear range extending to about 6 mM, giving a dynamic range of over 3 orders of magnitude for 0.1 mM methyl viologen. When stored in pH 7 phosphate buffer at 4 °C, the sensor shows almost no change in performance after operating for at least 2 months. A mechanism for the operation of the glucose sensor is also proposed.  相似文献   

18.
植物电信号测试研究进展   总被引:1,自引:0,他引:1  
综述了植物电信号研究的三个发展时期和未来研究趋势,广义的植物电信号概念就是能够记录到的植物细胞或组织电位发生波动以及相应的电流、电阻、电容等信号.论述了正常植物生理活动中的植物电信号为微弱低频信号,为小于5 Hz的"微伏"量级(1~999μV).破译绿色植物电信号特征就是深入解读植物生命信息,旨在为今后构建植物电信号自适应智能化控制系统,实现"节能减排"式农作物、蔬菜等的工厂化生产智能化自动控制研究奠定基础.  相似文献   

19.
不同液膜厚度下电偶腐蚀当量折算研究   总被引:2,自引:0,他引:2  
搭建薄液膜厚度测量与控制装置,采用微距参比电极后置法组建三电极体系,测量了在3.5%(质量分数,下同)NaCl不同液膜厚度下2024铝合金和TA15钛合金极化曲线和电偶电流,得到了不同厚度液膜下两种材料的电化学动力学参数;建立了基于薄壳电流分布的Comsol腐蚀仿真模型,得出了不同液膜厚度下的电偶电流以及电偶腐蚀与无电偶腐蚀时的当量折算系数。结果表明,利用仿真模型得到的电偶电流值与试验值吻合较好,50μm液膜厚度下的电偶电流约是溶液状态的25倍,随着液膜厚度的增大,电偶电流的下降速度逐渐增大,当液膜厚度达到1 000μm时,电偶电流趋近于溶液状态;50μm和100μm液膜厚度下电偶腐蚀折算系数约为无电偶状态下的5倍,当液膜厚度超过100μm时,折算系数急剧下降,到1 000μm时无论有无电偶腐蚀其折算系数均基本趋于1。  相似文献   

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