Root-mean-square voltmeters for a broadband input signal

The error of root-mean-square voltmeters in a broadband voltage measurement is considered, and proposals are made for standardizing the metrological characteristics of those voltmeters so that the error of measurement of the signals can be evaluated. Several versions of an automatic error estimater to be incorporated into the voltmeter circuit are described. Translated from Izmeritel'naya Tekhnika, No. 4 pp. 33–36, April, 1997.     

Evaluation of The Performance of Portable New Design High DC Voltage Measuring System up 40 kV

Portable DC high voltage (HV) measuring system up to 40 kV has been designed and built with DC HV probe and AC/DC voltmeter developed at TUBITAK UME (The Scientific and Technological Research Council of Turkey). The structure and construction of the HV probe and DC voltmeter for evaluating their performance are described. The comparison measurements have been done using the reference DC HV system up to 40 kV. The voltmeter described here was developed for using in the measurement or calibration of DC HVs with high input impedance greater than 100 MΩ. The voltage error obtained in comparison measurements is less than 100 μV/V at 40 kV.     

Method for the Thermal Characterization of PCM Systems in the Volume Range from 100 ml to 1000 ml

The storage of latent heat in phase change materials (PCM) is of great interest in many applications, for example in building applications. However, there is no standard method for the determination of the thermophysical properties of application-sized PCM specimens, i.e., specimens with sizes around 100 ml to 1000 ml. In order to close this metrological gap, a commercially available heat flow meter was modified to perform enthalpy measurements. The feasibility of this method was proven by performing comparative measurements on a stainless steel specimen using both the standard method DSC and the modified heat flow meter. Furthermore, measurements on a gypsum board with microencapsulated PCM were performed with the heat flow meter in order to determine the enthalpy. The coincidence with literature values is within ±4% which demonstrates that this method is a good choice for performing measurements on application-sized PCM specimens.     

基于Multi-TRL算法的传输线特征阻抗定标

在片散射参数的精确测量离不开传输线特征阻抗的精确定义。介绍了基于Multi-TRL算法的共面波导型传输线特征阻抗的定标方法,具体包括对Multi-TRL校准算法进行推导和优化得到传播常数,再利用传播常数计算得到传输线特征阻抗。在此基础上,开发了传输线特征阻抗提取软件wyb,并对特征阻抗测试结果进行了验证。测量片上参考标准RM8130上的校准标准,分别作为wyb软件和Wincal软件的输入量来提取特征阻抗。数据表明:在5～10 GHz频段内,特征阻抗幅值相差小于±0.6％,相位相差小于±0.55°;在10～40 GHz频段内,特征阻抗幅值相差小于±0.2％,相位相差小于±0.40°。     

Measurement of small rotation angles by using a parallel interference pattern

We propose a method for measuring rotation angles by using a parallel interference pattern. At two points on a parallel interference pattern reflected by an object, we detect phase changes in the reflected parallel interference pattern caused by rotations of the object. A high sensitivity, or a high ratio of the phase change to the rotation angle, 17 mrad/arcsec, can be achieved by determining the positions of two detection points. A high spatial resolution of ~0.5 mm is also obtained. We analyze the measurement error caused by the alignment of the parallel interference pattern and a random measurement error caused by the phase detection. The theoretical analyses and the experimental results make the characteristics of the method clear and show that the method has an accuracy of 0.2 arcsec for small rotation angles.     

Precision tube voltmeter for comparative measurements

Summary The simple method, justified theoretically in this article and verified in practice, of improving the linearity of tube voltmeters by a better setting of the zero, permits one to use mass-produced dc instruments without any recalibration of the scale, which is especially important when a recording instrument whose recalibration is difficult is used at the output of the voltmeter.     

Software Techniques to Improve Data Reliability in Superconductor and Low-Resistance Measurements

Software techniques have been developed to take low-amplitude data in various patterns, assign a figure of merit to a set of data readings, edit data for erroneous readings (or other experimental variations), and to alert the experimenter if the detected errors are beyond the scope of the software. Erroneous voltage readings from digital voltmeters, intermittent electrical connections, and an array of similar variations in data have been detected through the use of a data editor. The fixed-limit data editor removes readings that are inconsistent with the distribution of the majority of the data readings. The frequency of erroneous readings from a particular digital voltmeter ranges from 1 error per 100 000 readings to 1 error per 100 readings. The magnitude of the error can be as large as 3% of full scale with a zero volt input to the voltmeter. It may be necessary to have multiple meters measuring voltages in the same circuit in order to generate these erroneous readings. A systematic study was performed on the occurrence of the internally-generated erroneous voltmeter readings, and it was determined that the amount that a reading was in error scaled with one of a few parameters. The software techniques described here have been used in a variety of measurements, such as resistance-versus-temperature measurements made on cryoconductors or superconductors, and voltage-versus-current measurements made on superconductors to determine the critical current.     

A Precision Phase Meter

A new precision phase meter is described. The basic 20-c/s to 100-kc/s unit covers a 1-mV to 3-V range. This combines with a 1.5- to 45-Mc/s unit which operates between 300 ?V and 30 mV without adjustment. Any reference phase may be set to zero with an internal 360° phase shifter. Phase may be read from an internal meter or from a calibrated divider, but for a digital voltmeter, or for sweep measurements, an X-Y recorder may be used. Absolute accuracy is 0.5°.     

Electric field meter with a dipole antenna in an elliptically polarized electric field

A model of an electric field meter with a dipole antenna is analyzed. The model takes into account the fact that the meter incorporates other elements with a conducting surface in addition to the dipole antenna, viz.: a matching device, a signal cable, and a voltmeter. Alternative forms of the measurement equation are obtained, which differ in the error associated with the currents induced by the measured electric field on the braid of the signal cable and on the casing of the voltmeter. It is shown that this error can be eliminated partially or completely by performing additional measurements with the dipole antenna in different positions.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–48, February, 1994.     

Accuracy verification of a simple local three-dimensional displacement measurement method of DIC with two images coordinates

There are two methods applied for three-dimensional digital image correlation method to measure three-dimensional displacement. One is to measure the spatial coordinates of measuring points by analyzing the images. Then, the displacement vectors of these points can be calculated using the spatial coordinates of these points obtained at different stages. The other is to calibrate the parameters for individual measuring points locally. Then, the local displacements of these points can be measured directly. This study proposes a simple local three-dimensional displacement measurement method. Without any complicated distortion correction processes, this method can be used to measure small displacement in the three-dimensional space through a simple calibration process. A laboratory experiment and field experiment are carried out to prove the accuracy of this proposed method. Laboratory test errors of one-dimensional experiment are similar to the accuracy of the XYZ table; the error in Z-direction is only 0.0025% of the object distance. The measurement error of laboratory test is about 0.0033% of the object distance for local three-dimensional displacement measurement test. Test and analysis results of field test display that in-plane displacement error is only 0.12 mm, and the out-of-plane error is 1.1 mm for 20 m × 30 m measuring range. The out-of-plane error is only about 10 PPM of the object distance. These test and analysis results show that this proposed method can achieve very high accuracy under small displacement for both of laboratory and field tests.     

Features of the measurement of high-frequency ac voltage with electronic voltmeters

The features of the measurement of a high-frequency ac voltage with electronic voltmeters are considered for cases when the measured ac voltage is normalized at the input of the electronic-voltmeter probe or at the input of a special connector to which the voltmeter probe is connected.     

High-speed electromechanical digital voltmeter

Conclusions A method for raising the operating speed of dc digital voltmeters using contact elements is suggested and a schematic for a high-speed digital voltmeter supplied.The peculiarities of the above instrument consist of combining the relaxation relays (dc amplitude analyzers) with the compensating part of the voltmeter and in a special circuit for eliminating the possibility of an incorrect operation of a relay.If the required elements are added to the above circuit it is possible to make a multirange voltmeter with an automatic inducation of the polarity of the measured voltage. Difficulties may arise in adjusting the relaxation relays to low voltage operating levels. In this case the circuit may be supplemented by an additional amplifier with a gain of 10, and a negative feedback large enough to make the total effect of the zero drift and gain instability smaller than the minimum calibration of the instrument.     

基于自校法原理的DAC线性误差快速测试仪

本文讨论了自校法测试数－模转换器（ＤＡＣ）线性误差的两个难点：数学模型的建立和原始数据的测试。对测试仪作了误差分析，导出了估计测量误差的表达式，给出了对比实验结果。自校法测试ＤＡＣ无需对放大器的失调及增益做事先调整，也无需高准确度的标准源及数字电压表，适合于自动测试。     

Noise filtering of DC voltages in both the time and frequencydomain

We describe a method of obtaining a smaller statistical uncertainty on the DC component of a voltage signal by using a combination of time- and frequency-domain methods than by using time-domain averaging only. This measurement technique is compatible with precision DC voltmeters that poll the input signal less than 100% of the time. The frequency-domain strategy captures information during the time that the voltmeter is not reading the input signal. Alternatively, one can map out low frequency noise spectra using this approach     

Surface shape measurement of mirrors in the form of rotation figures by using point diffraction interferometer

The paper deals with the use of a point diffraction interferometer (PDI) to study the surface shape of rotation figures. The relations are given for the correspondence of the coordinates on the surfaces of an ellipsoid, a paraboloid and a hyperboloid as well as on an interferogram. Using PDI and Zygo white-light interferometer (WLI), we experimentally investigated the surface shape of the grazing incidence ellipsoid with the multilayer reflective coating on a wavelength of 0.154 nm with the following parameters: length is 55 mm, half-axis are 6 and 235 mm. The results coincided with an accuracy of 73 nm (RMS) without taking into account the PDI lateral resolution, and with an accuracy of 50 nm (RMS) with taking it into account, which ensures the local angles measurement accuracy of the ellipsoid-shaped reflecting surface at a level of 3 μrad. We think that this difference may be attributed to the limited lateral resolution of PDI and errors of frames stitching of WLI; nevertheless, we do believe that the PDI measurement accuracy is in the range of sub-μrad.     

NBS Provides Voltage Calibration Service in 0.1-10-Hz Range Using AC Voltmeter/Calibrator

Prompted by the need to support vibration and pressure measurements at frequencies down to 0.5 Hz (with expected future needs to 0.1 Hz), NBS now offers a calibration service for voltage standards and rms voltmeters in the range of 0.1-10 Hz. The means for the service is an "ac Voltmeter/Calibrator," an NBS-developed instrument containing an rms digital voltmeter and ac and dc voltage calibrators. The methods used to calibrate the ac voltage calibrator are discussed; also, application of the ac Voltmeter/Calibrator to the calibration of customers' voltage and voltmeter standards is described. Finally, a multifrequency voltage reference source with frequency-independent amplitude is proposed as a more suitable transfer standard than thermal voltage converters (TVC's) for the 0.1-10-Hz range.     

An algorithm for accurately estimating the harmonic magnitudes and phase shifts of periodic signals with asynchronous sampling

A digital sampling algorithm that uses two high-resolution integrating voltmeters in a master-slave configuration for accurately measuring the harmonic magnitudes and phase angles of two low-noise, low-frequency, arbitrary voltage signals is presented. It is shown that it is possible to measure up to 64 harmonic magnitudes of 60-Hz signals with an uncertainty of less than 13 /spl mu/V/V relative to the fundamental using commercial stable signal generators and high-resolution digital voltmeters. It is also possible to measure the phase shift between the fundamental components of two equally-synthesized 60-Hz signals with about 3.8% total harmonic distortion with an uncertainty of less than 2.5 /spl mu/rad. Even lower uncertainties can be obtained for low-distortion signals. The algorithm was applied to the measurement of the harmonics of periodic arbitrary signals generated by a commercial source. The differences between computed and measured values of harmonic magnitude suggest that stable digitally-synthesized signal generators can be used as calculable standards of harmonic distortion with an accuracy of less than 6 parts in 10/sup 5/ relative to the fundamental.     

用于变压器损耗校准的移相装置研制

针对变压器损耗测量系统(TLMS)校准中,对功率因数可调高压大电流信号源的需要,开展了移相技术研究及装置研制。装置在机理上利用希尔伯特变换,对输入信号进行卷积运算,得到正交参考信号;然后通过双参数的矢量合成技术生成相位可调的输出,从而产生不同功率因数的试验信号。基于此技术,搭建并实现了Compact RIO平台的移相装置。同时利用Compact RIO作为硬件平台、LabVIEW软件实现可视化操作,设计了相位测量仪器,并结合相角电压表Clark-Hess 2600对移相装置的稳定性和分辨率进行实验验证。实验结果表明:所研制的移相装置分辨率、稳定性及准确度优于0.001°。     

一种新型的交流阻抗计量标准装置

为解决任意阻抗模与阻抗角的交流阻抗的溯源问题,研制了一套新型交流阻抗标准装置,由交流阻抗标准源及交流阻抗标准表组成,在100Hz~1MHz、0.1Ω~1kΩ范围,可对RLC数字电桥、交流阻抗和实物阻抗进行校准,技术指标可以达到0.01%。采用直接测量法、替代测量法和等电位测量法,将交流阻抗标准溯源到实物阻抗标准、电压比例标准和相位标准上,形成了一条完整的交流阻抗溯源链。     

Measuring the root-mean-square values of random voltages with tube voltmeters

Conclusions The above examples indicate that in using standard tube voltmeters for measuring root-mean-square values of noise voltages it is necessary to take into account the distribution laws of their instantaneous values. Otherwise substantial errors can be made. By using the above technique it is possible to find the required corrections for every type of voltmeter and any kind of distribution law of a stationary random process.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 49–51, October, 1970.