Low-frequency accuracy of RMS voltmeters

The accuracy of rms voltmeters for nonsinusoidal input signals at the lower end of their frequency range and the conditions of maximum measurement error are investigated. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 30–33, February, 1997.     

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。     

Four Voltmeter Vector Impedance Meter Based on Virtual Instrumentation

In this paper, a digital vector impedance half-bridge meter based on virtual instruments is designed, implemented and tested. Here, not only the accuracy of the magnitude of the impedance is considered but, more importantly, its phase measurement accuracy. The meter utilizes a four-voltmeter method which is a basic modification of the well-known three-voltmeter method. The half-bridge is constructed with commercially available data acquisition (DAQ) board in the form of peripheral control interconnect cards incorporated in personal computers. The DAQ board is used only to acquire the voltages instead of using four separate voltmeters, while the excitation signal is produced by an integrated circuit signal generator. The main error in this method arises from the error in measuring the voltage values. Since the resolution of the DAQ board used here is 16 bits; expect that absolute errors due to A/D conversion will be around 0.305 mV for ±10 V range. Detailed error analysis of the method is included in the context of the paper. It is found that the errors in the impedance magnitude is fairly small and relatively less sensitive on the resolution of the voltmeters because of the relative measurements in the half bridge with a precise reference resistance. The original three voltmeter vector impedance meter has relatively large error in the phase especially in the small phase angles. To decrease the phase error to an acceptable range, one has to increase the resolution of the voltmeter appreciably, which makes them expensive. The other solution to reduce the error in the phase angle with less cost is to add a fourth voltmeter which acquires directly the small phase angles. In this case, it is found that, a much lower resolution voltmeter can be utilized while achieving an acceptable measurement accuracy of the impedance.     

High-temperature superconducting SQUID as calibrator of ac voltage dividers and LF voltmeters

The performance of a radio-frequency SQUID made of high-temperature superconducting ceramics as a calibrator of ac voltage dividers and LF voltmeters at frequencies up to 1 MHz is investigated. The measurement technique and errors are analyzed. The obtained results suggest that in principle the high-temperature superconducting device can reproduce the voltage divider scale with an error less than 10^–3 dB within an input signal range from several microvolts to several volts.Translated from Izmerital'naya Tekhnika, No. 9, pp. 47–50, September, 1995.     

Errors in strain measurement at high frequency

Two possible sources of error in strain measurement at high frequency were considered. The performance of the strain gauge itself was measured by comparison with a reference transducer. Several installations were shown to he satisfactory at up to 100 Hz hut another showed a progressive attenuation with frequency. Attempts to reproduce the fault with another installation were unsuccessful. The sources of error within the instrumentation were also considered and measurements made on the dynamic performance of several voltmeters.     

Instrument for Automatic Measurement of the Parameters of Solar Elements

An automated instrument for measurement of the parameters of solar elements based on an IBM personal computer, a digital potentiometer, and V7-21A digital voltmeters is described. The instrument produces a programmed specification of the load impedance of the solar elements in the range 0.002–800 , measurement of short-circuit currents up to 4 A, no-load voltages and the dark and light voltage-current characteristics as well as a calculation of the basic parameters of the solar elements with display of the results on a monitor and printer. The error of the measurements and of the calculation of the parameters of the solar elements is at most 0.4%.     

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.     

Digital voltmeter measuring circuits with parallel potential dividers

Summary The methods examined in this article for compensating the temperature error in supply sources and for stabilizing the input resistance of parallel potential dividers open up new possibilities for the application of these dividers in digital voltmeters with a range of 1–1000 V. Parallel potential dividers with a decimal scale made according to [5] are more suitable for use with low-resistance multivoltmeters.The processing of the readings of each decade in this instance can be carried out in four steps by the method illustrated in Fig. 6.     

Digital electromechanical voltmeters and ohmmeters

Conclusions The electrical numerical-readout measuring instruments have many important qualities and should in the near future acquire a correspondingly important place in our measurement technology. Electromechanical instruments with discrete static balancing (in a bridge compensator circuit) for voltmeters and dynamic balancing for ohmmeters with a gas-filled tube indicator display for each decimal place seem to be the most suitable types.     

Use of contactless vacuum thermal transducers in pressure measurements

Conclusions Investigations showed that the TVB-6 transducer can be used with standard measuring equipment (ÉPP-09, numerical voltmeters, etc.) in measuring absolute pressures of 1.33–1330 Pa. The relative mean square error of the transducer is 5%. Its service life is 100 h. The transducer, which is made commercially, is compact and cheap. However, it requires a highly stable feed current and its characteristic is nonlinear.Translated from Izmeritel'naya Tekhnika, No. 12, pp. 42–43, December, 1971.     

Semiautomatic installation for testing ac ammeters and milliammeters

Conclusions The principle of two calibrators first applied in an equipment for testing high-precision ac voltmeters [1] can also be used in the equipment for testing ammeters. This principle serves to obtain a high precision with a high productivity.Despite its relative complexity this equipment proved to be adequately reliable in use. Specialized installations for testing voltmeters and ammeters are more economical than universal ones for a large amount of testing.The principles on which the design of the installations for testing audio-frequency instruments are based [1] can also be used for constructing efficient high-frequency test installations.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 69–71, January, 1971.     

Voltage standards for testing ac voltage calibrators

Conclusions The V1-14 setup allows ac voltage measurement within the range from 0.1 to 300 V by the indirect comparison method and in the 0.1 to 100 mV range by substitution combined with comparison.The V1-14 setup conforms to 1st-class standards and can be used to test and certify both locally produced and imported voltage standards (calibrators), digital voltmeters, and also 2nd-class or less accurate thermoelectric converters.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 65–66, February, 1978.     

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.     

Means of transferring the dimension of the volt from a primary standard to solid-state voltage standards

A reference-voltage set and a Josephson-voltage converter developed at the D. L Mendelev All-Union Scientific-Research Institute of Metrology extend the range of reproducible voltages to 0.1–10 V. The error of reproducing and transferring the unit in the range 6–10 V by means of solid-state standards as well as digital voltmeters is less than 9.4·10^–9.Translated from Izmeritel'naya Tekhnika, No. 3, pp. 50–51, March, 1995.     

Techniques for Accurate Resistance Measurement in the Transient Short-Hot-Wire Method Applied to High Thermal-Diffusivity Gas

The accuracy of high-speed transient resistance measurements is an important issue particularly for measuring the thermal conductivity of high thermal-diffusivity (low-density) gases. This is because the hot-wire temperature rise against the logarithm of time is non-linear and can approach a steady state within the typical measurement time of 1 s. Two types of voltmeters are compared for use in the transient short-hot-wire method. Details of suitable procedures for taking accurate transient resistance measurements with either a two-channel high-speed analog/digital converter or a pair of integrating digital multimeters are presented.     

Features of the calibration and checking of diode compensation voltmeters at high frequencies

The results of a comparison of methods of calibrating and checking high-frequency voltmeters are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 45–46, November, 2006.     

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     

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.     

Use of microwave working power standards as voltage standards

The results of experimental investigations of the parameters of the indirectly heated thermoelectric transducers in microwave wattmeters are presented and their errors are estimated. It is shown that they are suitable for use as voltmeters to measure the active voltage in matched lines up to 2 GHz and can be used to calibrate voltage calibrators at rf and microwave frequencies. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 48–53, May, 1997.     

Progress in the United States on Electromagnetic Standards and Measurements at 30 kHz to 1 GHz, 1963 through 1965

A digest of highlights is presented on the most significant U. S. contributions to the measurement of attenuation, impedance, phase, field strength, thermal noise, current, and voltage at 30 kHz to 1 GHz. A total of approximately 30 contributions are digested. The following accomplishments are among them: a supersensitive detector for a complex-insertion-ratio measurement system having accuracies of about 0.0005 dB/10 dB at 30 MHz; exact equations for mutual and self-inductance of various combinations of filaments, tapes, and bars; a modified Twin-T-Bridge for measuring resistances of 100 to 10 000 ohms to 15 MHz; a set of Q-factor standards for frequencies to 45 MHz based on data and experience accumulated over five years; a unique adjustable characteristic-impedance coaxial line; measurement of Q's greater than 100 000 of cryogenic circuits at frequencies to 300 MHz; a novel Tee-junction to enable calibrations of voltmeters of any practicable input impedances with VSWR's ranging from 1 to 200, to 1 GHz and higher; a miniaturized dipole-antenna field strength meter, employing a semiconducting plastic transmission line, to measure complex nearzone fields of 0.1 to 1000 volts per meter, from 150 kHz to 30 MHz; and a prototype 3-MHz model of precision thermal noise-power comparators for an equivalent noise-temperature range of 75 to 30 000°K at accuracies of 0.2 to 1 percent.