时域噪声引起频谱误差的估计方法

在模拟信号数字化的过程中,由于采样器固有噪声和取样脉冲抖动以及量化噪声等因素的影响,取样量化后的数字信号被噪声污染。对含有噪声的数字信号进行时频变换时,必然引起频谱误差。本文讨论如何利用误差功率估计由时域噪声引起的频谱误差问题。得出误差功率是频谱幅度误差的方差上限这一结论,该结论对评估数字信号的质量有参考价值。     

用正弦规校准数显倾角仪示值误差的不确定度

数显倾角仪是进行角度测量常用的计量器具,为保证倾角仪计量性能的准确可靠,利用正弦规对其进行角度测量.文章重点介绍了该校准方法和示值误差的不确定度评定.     

基于球杆仪和光栅尺的工作台精度调整

用球杆仪和光栅尺同时测量了两轴联动精密工作台的走圆运动．结果显示,光栅尺的主要误差源是测量噪声和定位误差,球杆仪的主要误差源是定位误差．尽管对于单轴实时位置反馈来说,光栅尺的测量精度已经足够,但是两个方向光栅尺的测量数据不能反映两轴间的相对精度．通过对光栅尺和球杆仪测量的工作台走圆运动测量数据的分析,建立了测量系统的数学模型,在此基础上解耦并识别出了球杆仪和光栅尺的定位误差．提出了根据光栅尺倾角误差实现工作台精度调整的策略．     

双啮仪自动检测装置的改造

通过对双啮仪进行改造，使之能自动检测一齿和一周径向综合误差，且检测结果直接由数显装置读取。本文介绍改装的方法。     

电子数显指示表示值误差测量结果的不确定度评定

本文介绍了用全自动光栅式指示表检定仪检定数显指示表示值误差测量结果的不确定度评定方法。     

电子水平仪节距法测量平直度的定位误差

数字式电子水平仪节距法测量平直度时，其测量不确定度的主要来源有示值误差，数显量化误差，测量重复性，定位误差等四项。本文讨论定位误差的估算，分析影响定位误差的主要因素，并提出抑制定位误差的方法。     

JJF(浙)1057—2010《数显倾角仪校准规范》问题探讨

文章针对JJF(浙)1057—2010《数显倾角仪校准规范》在标准器的选型、示值误差正反行程校准存在的表述模糊笼统等问题,提出不同意见及修改建议。     

数字模拟转换器阶梯波量子误差补偿

数字模拟转换器产生阶梯波中的基波分量用于精密测量时,量化误差是一个重要的影响因素。在理想转换的基础上,分析了这种影响,进而提出了量子误差的补偿方法,并以实验结果验证补偿的可能性及其效果。最后讨论了数字模拟转换器产生阶梯波量化误差的性质。     

基于球杆仪的旋转轴几何误差测量和辨识

通过圆弧测量轨迹, 移动球杆仪测量球心在旋转工作台上3个安装位置的9项误差, 采用齐次变换理论建立几何误差辨识模型, 引入系数矩阵条件数进行安装参数的优化选取, 提出一种辨识旋转轴4项位置和6项运动误差的方法。最后, 在四轴数控加工中心上进行了测量和验证实验, 该方法可辨识出全部的几何误差项, 通过对几何误差计算出的预测值和球杆仪的测量值的比较, 预测值的绝对误差小于0. 003 mm, 具有辨识精度高、测量省时的优点。     

大量程百分表示值误差的分段检定

本文提出了在百分表检定仪上对大量程百分 表的示值误差进行“分段检定”的方法,并通过实例和误差分析,验证了检定方法的可行性。     

$SigmaDelta$ADC-Based Frequency-Error Measurement in Single-Carrier Digital Modulations

This paper deals with the functional-block architecture implementing the new method to measure the carrier frequency error of the single-carrier digital modulations. The method is able to operate on the modulations$M$-ary amplitude shift keying,$M$-ary phase shift keying, and$M$-ary quadrature amplitude modulation used in the telecommunication systems. The functional-block architecture obtained from the software-radio (SR) architecture is based on the cascade of the analog-to-digital converter (ADC), the digital down converter, and the base-band processing. Looking at the implementation in measurement instrumentation, the performance of this cascaded architecture is investigated by considering three different ADC architectures. They are based on 1) pipeline; 2) single quantizer loop Sigma-Delta$(SigmaDelta)$modulator; and 3) multistage noise shaper (MASH)$SigmaDelta$modulator. Numerical tests confirm the important rule of the ADC in this architecture and highlight the interesting performance of the MASH-based$SigmaDelta$modulator for use in advanced measurement instruments.     

Uncertainty of Positioning and Displacement Measurements in Quantum and Thermal Regimes

We analyze the performance of position-sensing devices and of distance- or displacement-measuring instruments, and we find that the ultimate uncertainty at the quantum limit of detected signal is given by the same expression in all cases, namely, a characteristic length L_c divided by radicNph, the square root of the number of photons detected in the time interval of the measurement. We derive the expression of the length L_c for well-known position-sensing devices (the quadrant photodiode and the position-sensing detector) and for several measuring instruments (pulsed and sine-wave-modulated rangefinders, triangulation telemeter, laser interferometer, and the optical rule). We also extend the analysis of the uncertainty results to the thermal regime case of detection, i.e., when the detector dark current and preamplifier noises are dominant with respect to quantum noise.     

A real-time electro-optic handy probe using a continuous-wave laser

This paper describes a real-time electro-optic (EO) probe system that can be directly connected to digital oscilloscopes, spectrum analyzers, and other widely used instruments. The probe incorporates a balanced optical receiver with two high-speed InGaAs p-i-n photodetectors (PDs) to reduce noise, and optical isolators to decrease the light reflected from the optics back to the laser diode (LD). To increase sensitivity, we employ cadmium telluride (CdTe), which has a large EO coefficient, and a high-power 1.3-μm distributed-feedback (DFB) LD as a continuous-wave (CW) laser source. We used it to measure eye diagrams at 1 Gb/s that were displayed on a digital oscilloscope. In addition, when connected to a spectrum analyzer, the probe significantly simplifies frequency-domain analysis. We demonstrate the measurement of electric nearfield distribution radiating from a two-layer printed circuit board (PCB) and a cellular phone. The result shows that the probe system is a potential candidate for electromagnetic interference (EMI) instruments     

Analysis of the random errors of digital algorithms for measuring the frequency of laser-doppler anemometers by numerical modeling

An analysis is made of the errors of digital algorithms for measuring the frequency of the Doppler signal of a laser-Doppler anemometer (LDA) by numerical modeling. An examination is made of methods of evaluating the period of the high-frequency duty cycle of a single-particle signal from an LDA with respect to the coordinates of the “zeros” of the process. Methods of evaluating the frequency of the signal from the position of the maximum of the modulus of spectral density are also discussed. Results are presented from studies of the dependence of the measurement error on the parameters of a discretized LDA signal and the signal/noise ratio. The conditions necessary for restricting the maximum measurement error to 0.1–0.3% are determined. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 36–38, July, 1995.     

A weak magnetic field measurement system using micro-fluxgate sensors and delta-sigma interface

This paper presents a weak magnetic field measurement system using micro-fluxgate (FG) sensors and a sensor signal processing technique using the delta-sigma modulation in the negative feedback loop. The feedback of the lowpass filtered bitstream output of a delta-sigma modulator to the magnetic field improves system linearity, hysteresis, and stability. In spite of the fact that the second-order delta-sigma modulator is used, the third-order noise shaping can be obtained in the digital output bit-stream by the use of an integrator in the loop. This improves the SNR of the digital output. The measured noise of the implemented system meets the measured noise of the FG sensing element itself. The weak magnetic field in the range of the Earth's magnetic field is successfully measured. The nonlinearity error is less than 0.4% in the range of /spl plusmn/100 /spl mu/T.     

提高圆度误差分离精度的措施

以圆度误差分离技术为例,着重分析了影响分离精度的因素,提出了改善分离精度的数据有效性检验、集合平均、无附加相移数字滤波等措施。同时应用实例说明所述措施的必要性及实用性。     

Digital Instrumentation for the Time Integral of the Square of a Slowly Fluctuating Voltage

A portable digital instrument is described that provides a decimal readout of 1) the time integral of the square of a fluctuating voltage and of the measuring time on two decimal displays, and 2) the amplitude distribution of the voltage. The instrument has no low-frequency limitations. For periodic inputs, measurement may take place over one cycle. For either periodic or random inputs, measurement may be made to commence on a start signal and run for a programmed time. Readout is available immediately at the end of the measuring time, so that the instrument can be used in on-line real-time process control. The voltage under measurement is sampled systematically, and the sampled data are processed using a unique special-purpose digital computer. The paper describes the principles on which measurements are based, and the design and error characteristics of an instrument in which, for most waveforms (e. g., sine, ramp, white noise), the maximum error is in the region of 1 percent and the upper frequency limit is about 1 kHz.     

利用LabVIEW和国产模入卡实现信号的采集与分析

介绍通过调用动态连接库,在LabVIEW环境下,利用国产模入卡KPCI-814实现数据采集的方法,利用混有噪声的模拟信号,采用LabVIEW自带工具包实现了信号的数字滤波与频谱分析,系统将为超导量子干涉器（SQUID）在弱磁场测量中的应用提供良好的信号采集、处理与分析手段。     

应变测量仪的自校准电路设计及应用

为解决应变测量仪在使用分流法进行校准时存在的费时耗力效率低下、精度不足等问题,实现应变信号的高精度采集,研究并设计了低漂移、低噪声的自校准电路,程控配置采集通道和校准信号,拟合出采集信号和自校准信号之间的函数关系式,获取校准系数,对应变测量结果进行校正,有效降低应变测量的温度漂移误差和噪声误差,满足应变测量仪精度的指标要求。     

Approaching the fundamental noise limit in Mo/Au TES bolometers with transverse normal metal bars

Recent efforts in the Transition Edge Sensor (TES) bolometer/calorimeter community have focused on developing detectors whose noise properties are near the fundamental limits. These include the in-band phonon noise, the out-of-band Johnson noise, and the 1/f noise. We have investigated the noise performance of Mo/Au-bilayer TES bolometers designed for infrared detectors. These detectors use normal metal regions for the suppression of excess noise, which are oriented either parallel to (“bars”) or transverse to (“stripes”) the direction of current flow. Two nearly identical detectors, one with stripes and one with bars, were fabricated at the NASA/GSFC detector development facility. Significantly lower noise is found with the normal metal regions oriented transversely. We compare the detailed noise measurement and quantitative analysis of the noise level in each device as a function of the detector resistance. Our preliminary result is that the best detector features only moderate excess noise in both the in-band region and in the out-of-band region. This noise performance is suitable for instruments with multiplexed TES arrays, such as GSFC's FIBRE and SAFIRE.