High-Accuracy Analog Measurements via Interpolated FFT

By use of an interpolated fast-Fourier-transform (FFT) algorithms are developed for multiparameter measurements upon periodic signals. Eight pertinent measurements, such as fundamental frequency, phase, and amplitude, are made with enhanced accuracy compared to existing algorithms, including tapered-window-FFT algorithms. For the more general case of nonharmonic multitone signals also the method is shown to yield exact amplitudes and phases if the tone frequencies are known beforehand. These measurements are useful in a variety of applications ranging from analog testing of printed-circuit boards to measurement of Doppler signals in radar detection.     

A High-Accuracy Digital Instrument Design for DC Measurements

A high-accuracy self-calibrating digital instrument design has been developed in order to make available the inherent efficiency advantages of conventional digital meters, but without their limitations in accuracy, reliability, or certifiability. The new instrument can extend the advantages of automation to many testing, quality control, and standards laboratories where heretofore only high-quality manually balanced instruments could be used. Automation at this level of accuracy can eliminate serious cost bottlenecks in the testing of precision devices such as Zeners, resistors, A/D and D/A networks and converters, standard cells, regulated power supplies, voltage and current sources, digital and differential voltmeters and potentiometers, and the dc output of many precision transducers. The paper describes a number of applications of this new type of digital instrument and presents samples of the type of automatic test data obtained.     

基于GPS和高精度实时时钟的时间同步方法

时间同步在航天测控、卫星遥感、军事靶场、视觉测量、电力运输等领域有重要意义.针对计算机时间系统分辨率低的问题,提出使用全球定位系统(GPS)接收机的整秒脉冲信号和串口时间信息,作为高精度的时间源,具有高频率稳定性的时间模块与该时间源同步;计算机通过RS232串口从时间模块获取时间信息,利用模拟精密时间协议时间同步方法的过程,测量串口通信过程中的延时并补偿,完成计算机高精度时间同步.通过整秒脉冲比对的方法测试时间同步的精度.实验表明,时间同步方法的同步精度优于500μs.     

Ferroelectric Switching Time Measurements

A simple method is described for determining field-induced polarization reversal times in ferroelectrics ranging from seconds to nanoseconds without the use of an oscilloscope. The procedure consists of 1) setting some selected reference state of polarization, preferably by recording a hysteresis loop which is terminated at the reference state, 2) applying a pulse field of known amplitude and duration to reverse a portion or all of the polarization, and 3) tracing a new hysteresis loop. The difference in polarization state between the starting point of the second loop and the termination point of the first is the amount of polarization switched by the pulse field. Data consist of charge densities ?Pr switched by the pulse fields of various amplitudes E and durations t. From ?Pr versus E plots, the field corresponding to half-switching of the polarization is read for each pulse length applied and a log/log plot of the half-switching time t1/2 versus E is constructed. These log/log plots for lead zirconate-titanate ferroelectrics generally yield, each, three linear segments in which, with increasing field, t1/2 is proportional to E-?, E-?, and E-? and ?>?>?.     

Time Domain Reflectometer Return Loss Measurements

Equations are derived for the exact identification of a transmission line discontinuity that can be represented by an equivalent circuit consisting of one or more cascaded, series-inductive, parallel-capacitive, and series-transmission-line elements. Equations are presented for determining frequency domain return loss from time domain reflectometer data and the frequency limitations for this method of discontinuity evaluation are discussed.     

在时、频测量中的倍增器

本文阐述了倍增原理，详细分析了多级倍增器的噪声门限以及确定它们的测量上限，还介绍有关倍增器里的关键电路－倍频器及其影响和倍增器在时、频测量中的应用．     

Relaxation Time Measurements by an Electronic Method

In many experiments, one is faced with the problem of measuring the time constant of decaying signals. The paper describes a simple electronic system that permits the direct measurement of time constants. The system was used in connection with relaxation experiments on hydrogen and rubidium masers and was found to operate well. The use of a computing counter in the systems gives the possibility of making averages on several experiments and obtaining the standard deviation of the results from the mean. The program for the computing counter is given.     

Fourier Analysis From Networked Measurements Using Time Synchronization

Can frequency-domain analysis be made from time-domain measurements taken over networks with poor temporal characteristics, that is, poor or no guarantees about when commands or data will be delivered, such as the public Internet? Our answer to this question is ldquoyes.rdquo Provided that the times that samples are taken are measured accurately, Fourier analysis can be performed, even when the samples are taken at nonuniform intervals. Due to the tendency of packet delays in networks to have long-tailed probability distributions, it is also desirable not to make assumptions concerning the probability distribution of the time intervals between samples. We show that the combination of network time synchronization and stabilization of measurement apparatus using the IEEE 1588 Protocol and the methods for Fourier analysis of nonuniformly spaced data from the literature are sufficient to provide spectra from measurements taken with networked sensors. The key steps of our method are an accurate timestamping of the measurements followed by a Fourier transform. The Fourier transform may be accomplished by either resampling the measurements into a constant rate so that fast Fourier transforms may be used or performing a least squares fit of a sine/cosine basis to the data. Both approaches were tested using measurements taken over the public Internet using measurement apparatus synchronized using IEEE 1588.     

A High-Accuracy Computer-Aided Profile-Measuring Machine

This paper describes a system for the high-precision, rapid measurement and evaluation of rotatable object profiles such as cam's. The data are acquired off-line by sampling with a high-resolution optical encoder and are recorded on magnetic tape via an incremental recorder. The recorded data are subsequently analyzed by a computer program to provide the required parameters. The system is characterized by ease of operation, high precision, repeatability, and relative simplicity. It makes available an automated measurement capability that was previously only possible by manual methods on an optical lathe or a measuring engine.     

10-kV High-Accuracy DC Voltage Divider

A high-accuracy voltage divider based on the Hamon/Rayleigh ratio principle has been made for the absolute measurement of the volt and also for building up the voltage scale to 10 kV. It is composed of 100 equal resistors of nominal value 100 k? and an adjustable 100-k? resistor with taps at 10 and 1 k?. By using appropriate connections, a total 10-M? divider with 1-k? output is constituted in which various voltage ratios up to 104 can be obtained. A guard circuit is provided to minimize the leakage currents. The calibration of the divider is simplified by using parallel or series-parallel connection of resistance elements so that all comparisons are made at a ratio of 1:1. For 10 kV only, two comparisons are required. The measurement of performance of the divider and the analysis of errors have been made. The most important factor affecting the voltage ratio is self heating, for which a correction is necessary. The total error would be less than 0.58 ppm.     

高精度氧分析仪性能简介

以美国Delta F公司的氧分析仪为例,介绍了库仑电解式氧分析仪的工作原理、性能特点及应用领域。     

Frequency–Time Method of Processing Phase Measurements in Geophysics

A frequency–time method is proposed for analyzing geophysical phase information whose implementation approaches the results of the operation of an ideal filter. The method is based on the principle of expanding an observed signal over a system of basis functions. The procedure developed makes it possible to determine the phase of the signal and to estimate the operational stability of the phase measuring system. The procedure can be used when designing geophysical measuring devices utilizing optical phase measurements.     

捷变正弦信号源波形建立时间的精确测量

针对正弦信号源捷变状态切换后的建立时间、开机后波形建立时间以及过载恢复时间等的精确测量问题,提出了一种基于局域波形四参数拟合的测量分析方法,然后将拟合模型参数拓展到全局,进而获得拟合回归波形与过渡过程波形的回归残差波形。该波形的收敛过程反映了正弦波建立过程中的残差收敛变化过程。以它为目标对象,加上主观设定的建立时间的条件判据,可以获得正弦建立时间的起始和终止两个时刻点,最终获得完整的正弦信号建立时间。在两组不同条件下的状态切换实验结果,验证了该方法的有效性和可行性。该方法也可以推广应用到脉冲调频、脉冲调幅、脉冲调相、捷变频信号的建立时间测量评价中。     

线性特征值问题的高精度矩阵摄动法

线性特征值问题摄动重分析的基本理论已趋于成熟。本文进一步探讨了提高摄动计算精度的策略,提出了一种分步摄动一摄动迭代算法。通过实例计算表明,该算法可在结构具有大修改量的情况下有效地实现广义特征值问题的高精度重分析。     

Hindered Settling in Unflocculated Suspensions

Abstract

The hindered settling of three sizes of microcapsules suspended at four different concentrations in silicone fluids with four viscosities was determined at 25°C in suspensions.

The viscosities of the various suspensions determined by a Stormer Viscometer indicated pseudoplastic behavior. A viscosity constant was calculated using the power law of the form

ηs^N = ηk^G

The sedimentation rate of suspensions of microcapsules was determined at low Reynolds numbers. An equation

V_s = [(ρ_s - ρ)g/18η] · f(d,C, η_k)

was proposed in which the exponent of [(ρ_s - ρ)g/18 η] was shown to be one. Various sedimentation parameters were fitted by multiple linear regression method to a curve. The empirical equation obtained was

V_s = [(ρ_s - ρ)g/18 η] d^1.63 (1/C^1.27) ηk ^0.07 e^?4.31

A comparison of sedimentation rate against suspension concentration was made for values calculated from the classical Stokes equation, experimental values, and predicted values from the fitted equation.     

Settling of a bidisperse suspension

The influence of the fractional composition on the settling velocity of a bidisperse suspension is investigated theoretically. The average particle radius of a settling bidisperse suspension is calculated.     

Analysis of Time of Arrival Estimation Using Wideband Measurements of Indoor Radio Propagations

Using time of arrival (TOA) to determine the distance between the transmitter and the receiver is the most popular technique for accurate indoor positioning. The accuracy of measuring the distance using this method is sensitive to the bandwidth of the system and the multipath condition between the wireless terminal and the access point. In general, as the bandwidth increases beyond a certain value, it is expected that the measured TOA error approaches zero. However, for the so-called undetected direct path (UDP) conditions, the system exhibits substantially high distance measurement errors that cannot be eliminated with the increase in the bandwidth of the system. In this paper, we provide an analysis of the behavior of superresolution and traditional TOA estimation algorithms in line-of-sight (LOS), non-LOS, and UDP conditions in indoor areas. The analysis is based on wideband frequency- domain measurements of the indoor radio channel propagations in several indoor areas, with special attention to the UDP conditions.     

Design and Error Analysis of High-Accuracy DC Voltage-Measuring Systems

A systematic analysis of the errors inherent in the application of a resistance voltage divider to the measurement of high voltages is presented. The effects of potentiometer errors, leakage errors, and rod resistance are considered in turn. A newly developed high accuracy volt box providing output voltages of 0.5 v, 1.0 v, and 1.5 v for all input voltages ranging from 1.5 to 1600 v in steps of 0.5 v is then described.     

The Design of an Automated, High-Accuracy Antenna Test Facility

This paper presents the step-by-step application of proven far-field range and instrumentation design techniques to a specific antenna measurement problem, describes the resulting facility design, and presents the predicted measurement uncertainty. Fundamental electromagnetic design criteria for an outdoor, far-field facility establish minimum dimensional requirements for the range design and limiting values of source-antenna directivity. Electromagnetic compatibility of the facility is assured by frequency coordination with existing and planned services in the area surrounding the available site. Additional design constraints for this facility included restricted measurement time, reduction of spurious test enclosure effects, limited available terrain, and required data quality. In this case, the required range length is in excess of 6500 ft, and paraboloidal source antenna diameters up to 23 ft are required. The frequency coordination problem was solved by exploiting the natural terrain features and configuring the measurement system as "test-on-transmit." Signal and reference paths share the same range cable. The quantity of data that must be handled in the available measurement interval required the use of a computer-based measurement system.