Automation and Evaluation of Two Different Techniques to Calibrate Precision Calibrators for Low Frequency Voltage Using Thermal Devices

Low frequency (LF) voltage and current are important parameters in electrical metrology. The standards for LF voltage and current are established by assigning AC–DC transfer difference to thermal devices, i.e. thermal converters or thermal transfer standard along with current shunts. Automated calibration systems have been developed based on Null method and measurement technique developed by Budovsky for calibration of precision calibrator in LF voltage and current against thermal devices. The technique based on the Algorithm developed by Dr. Ilya Budovsky (National Metrology Institute (NMI), Australia) has been compared with the conventional null technique. Indigenously developed software has been used to calibrate the precision calibrator in the entire LF voltage and current range using Holt thermal converters and current shunts. Calibration results at 1 V, 10 V in the frequency range from 10 Hz to 1 MHz as well as calibration results of 1 A in the frequency range from 40 Hz to 10 kHz are presented in this paper. These result shows that the measurement technique developed by Budovsky has reduced the complexity of AC–DC transfer measurements, measurement time and the uncertainty in measurement.     

IC fabrication-compatible processing for instrumentation andmeasurement applications

The solid-state sensor field is maturing and an increasing number of applications is being served. Nevertheless, the available infrastructure and technology have found only few applications within the field of instrumentation and measurement (I&M). Therefore, the aim of this paper is threefold: (1) to categorize the various sensor processing strategies that are available; (2) to provide a representative overview of what different silicon sensor processing techniques are available; and (3) to point out their potential for use in metrological applications. To this end, a number of examples of (potentially) successful micromachined devices for metrology are discussed. The key considerations in this application area are: (1) the mechanical material properties of silicon and (2) the on-chip cointegration of the entire reference system     

Stability of microelectromechanical devices for electricalmetrology

Microelectromechanical systems (MEMS) have been recently proposed for realizing several references in electrical metrology. Such devices are formed from micromachined electrodes of which at least one is supported by a compliant structure such that an electrostatic force between two electrodes displaces the moving electrode. The properties of these electromechanical devices can be very stable if they are fabricated from single-crystalline silicon and sealed hermetically in a low-pressure atmosphere. In comparison to several semiconducting reference devices, micromechanical components are large in size and consume a negligible power. Thus, a low 1/f noise level is expected. The proposed MEMS electrical references include a DC and an AC voltage reference, an AC/DC converter, a low-frequency voltage divider, a microwave and millimeter-wave detector, a DC current reference, etc. Measurements on a prototype for a MEMS DC reference are discussed. The stability is presently limited by charge fluctuations on the native oxides of electrode surfaces. Preliminary results show relative fluctuations below 1 μV/V     

Fuel cell power conditioning for electric power applications: a summary

Fuel cells are considered to be one of the most promising sources of distributed energy because of their high efficiency, low environmental impact and scalability. Unfortunately, multiple complications exist in fuel cell operation. Fuel cells cannot accept current in the reverse direction, do not perform well with ripple current, have a low output voltage that varies with age and current, respond sluggishly to step changes in load and are limited in overload capabilities. For these reasons, power converters are often necessary to boost and regulate the voltage as a means to provide a stiff applicable DC power source. Furthermore, the addition of an inverter allows for the conversion of DC power to AC for an utility interface or for the application of an AC motor. To help motivate the use of power conditioning for the fuel cell, a brief introduction of the different types, applications and typical electrical characteristics of fuel cells is presented. This is followed by an examination of the various topologies of DC-DC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for high-voltage/high-power applications are also reviewed.     

Systematic Error Analysis of Stepwise-Approximated AC Waveforms Generated by Programmable Josephson Voltage Standards

We have measured stepwise-approximated sine waves generated by a programmable Josephson voltage standard (PJVS) with several different output configurations. These data are analyzed to characterize the dominant error mechanisms for RMS applications, such as ac–dc difference measurements of thermal voltage converters (TVCs). We present detailed explanations of the fundamental causes and consequences of systematic errors that arise from transitions and consider the overall uncertainties for PJVS ac metrology using this synthesis method. We show that timing-related errors are sufficient to make this waveform synthesis approach impractical for RMS audio-frequency applications. The implications of providing the load current required by devices of low input impedance, such as TVCs, are also discussed.      

Precision average-sensing AC/DC converters

Various configurations of average-sensing AC/DC converters for precision AC voltage measurements are described. Due to the unique electrical configurations in which the influence of the inaccuracy of ratio resistors is suppressed, these converters have high accuracy (better than 0.01%) and resolution (0.0001%) at medium frequencies. Their frequency range is from 10 Hz to 1 MHz, with a settling time less than 1 s     

Silicon multi-branch nanostructures for decent field emission and excellent electrical transport

We report on the synthesis, field electron emission and electric transport properties of a novel nanomaterial: ordered arrays of crystallized silicon multi-branch nanostructures. A decent field electron emission with relatively low turn-on field of 3.16 V μm?1 and high field-enhancement factor of 1252 was received for the silicon nanobranches. The relevancies between field-emission current-voltage characteristic, turn-on field, threshold field and sample-anode distance have been thoroughly analyzed. In addition, electrical transport measurements revealed a small electrical resistance of 0.51 MΩ for as-prepared silicon nanobranches. In contrast, by improving the silicon nanobranch-electrode contact, vacuum annealing dramatically reduced the electrical resistance, by a factor approaching two, while thermal oxidation resulted in a much higher resistance due to the amorphous oxide coating of the silicon nanobranches, both of the current versus voltage curves became more linear and symmetrical, and the transport stability was obviously improved.     

Low-distortion audio-frequency AC reference standard with AC-DCoutput switching capability

A digital AC voltage standard with well-known AC-to-DC output voltage difference is described. The proposed feedback configuration can effectively measure and correct for loading effects, caused by a measuring device. Because the AC standard can generate AC and DC voltages at the same output terminals, the automatic measuring setup for thermal voltage converters (TVC) is considerably simplified. The state-of-the-art stability of output voltage enables it to be used for intercomparison purposes     

A new power standard for audio-frequency measurements

A thermal power comparator for audio-frequency measurements is presented. It is essentially a double-bridge-type multiplier that consists of two multijunction thermal converters that contain two heaters. Together with a precision inductive voltage divider and current transformer for extending the voltage and current range, the comparator ensured a high-precision power standard with an AC/DC transfer error of less than 15 p.p.m. in the audio-frequency range     

电磁计量学研究进展评述

2019年5月20日,国际单位制(SI)实现了7个基本单位均以基本物理常数为基准,计量体系迎来“计量单位量子化”和“量值传递扁平化”重大变革。电磁计量在计量学领域中占据极为重要的地位,开展电磁计量研究对保持我国量值传递先进性、促进计量学新发展具有重要意义。介绍了电磁计量的基本特性,综述了其在量子标准及芯片、能量天平、交流电量计量、交流阻抗及比率计量、高压计量、磁参量计量等方面的国内外发展现状,对电磁计量科学技术的发展趋势进行了展望。     

Design and metrological applications of a low noise, high electrical isolation measurement unit

A digitally controlled voltage generation and measurement unit optimised for high-precision electrical metrology is described. It is optically isolated from the controlling computer and contains specially constructed isolated power supplies allowing continuous operation without the need to recharge batteries. The source has a simple microcontroller that is pre-programmed with firmware to control operation and to carry out simple repetitive measurement tasks, such as generation and quantisation of signals using uniform sampling. The merits of the developed unit are demonstrated by three example applications: (i) the application of the unit to control a Josephson voltage standard, (ii) the implementation of a transfer standard for the calibration of the electronic instrumentation of fatigue testing machines traceable to the primary electrical standards and (iii) the force measurement of an ion thruster traceable to the primary electrical standards at the industrial user level.     

Sialons and related nitrogen ceramics

Although silicon nitride is at present a leading contender for gas turbines and other hightemperature engineering applications, it is only the first of a wide field of nitrogen ceramics, other members of which offer better prospects for technological exploitation. “Sialons” are phases in the Si-Al-O-N and related systems and are comparable in variety and diversity with the mineral silicates. They are built up of one-, two-, and threedimensional arrangements of (Si, Al) (O, N)₄ tetrahedra in the same way that the fundamental structural unit in the silicates is the SiO₄ tetrahedron. These new oxynitrides include structure types based uponα andΒ silicon nitrides, silicon oxynitride, aluminium nitride and silicon carbide, eucryptite, spinel, melilite and apatite. They are being explored for their thermal, mechanical, chemical and electrical properties.     

Electrical properties of polycrystalline silicon and zinc oxide semiconductors

Polycrystalline silicon and zinc oxide ceramic are important electronic materials. The electrical properties which determine the applications of polycrystalline silicon in integrated circuits and solar cells and that of ZnO ceramic in varistors are due primarily to grain boundary effects in them. A large amount of information in this area has already been gathered in literature but the quantitative understanding of grain boundary effects in these materials is not yet complete. In this review the important aspects of grain boundaries and their effects on transport and photoelectric properties of polycrystalline silicon and on the I–V characteristic of ZnO varistors are discussed. An erratum to this article is available at .     

Effect of annealing temperature on electrical and nano-structural properties of sol–gel derived ZnO thin films

Zinc oxide (ZnO) thin films have been prepared on silicon substrates by sol–gel spin coating technique with spinning speed of 3,000 rpm. The films were annealed at different temperatures from 200 to 500 °C and found that ZnO films exhibit different nanostructures at different annealing temperatures. The X-ray diffraction (XRD) results showed that the ZnO films convert from amorphous to polycrystalline phase after annealing at 400 °C. The metal oxide semiconductor (MOS) capacitors were fabricated using ZnO films deposited on pre-cleaned silicon (100) substrates and electrical properties such as current versus voltage (I–V) and capacitance versus voltage (C–V) characteristics were studied. The electrical resistivity decreased with increasing annealing temperature. The oxide capacitance was measured at different annealing temperatures and different signal frequencies. The dielectric constant and the loss factor (tanδ) were increased with increase of annealing temperature.     

Thermal Converters for Audio-Frequency Voltage Measurements of High Accuracy

The ac-dc differences of a reference group of thermoelements have been evaluated at audio frequencies to a few parts per million (ppm) at currents from 5 to 20 mA. A technique for comparing the ac-dc differences of two thermoelements with an uncertainty of about 2 ppm has been developed. Two 5 mA thermoelements are used with a plug-in set of resistors of computable reactances to form thermal voltage converters for voltage measurements. With this same technique adjacent ranges of these converters can be compared to step up from 0.5 to 500 V to better than 10 ppm.     

Compact, very low voltage, temperature-independent reference circuit

A compact, very low voltage, temperature-independent reference circuit, which is based on the thermal properties of bipolar junction transistors in the saturation region is presented. The new circuit operates from a minimum power supply of less than 1V and provides a reference voltage with a nominal thermal drift of ~30 ppm/degC in the temperature range between -40 and 110degC. The proposed circuit has been integrated on silicon by a 0.35 mum CMOS technology and a reference voltage with a measured untrimmed thermal drift of ~100 ppm/degC has been reported. The new voltage reference occupies a silicon area of only 3,500 mum², shows a power consumption of <30 muW and its DC power supply rejection is better than 65 dB     

Comparison of SEM and HRTEM CD Measurements Extracted From Test Structures Having Feature Linewidths From 40 to 240 nm

Critical dimension (CD) measurements have been extracted from SEM and high-resolution transmission electron microscopy (HRTEM) images of the same set of monocrystalline silicon features having linewidths between 40 and 240 nm. The silicon features are incorporated into a new test structure that has been designed to facilitate this type of CD metrology study. Major improvements to previously reported HRTEM sample-preparation and fringe-counting procedures have been implemented. The purpose of this paper is to make a preliminary assessment of the calibration statistics of SEM transfer metrology when HRTEM is used as the primary metrology in CD reference material calibration. The linearity and the correlation of the regression between HRTEM and SEM measurements were very encouraging. However, further study of the calibration statistics, from which uncertainty estimates of the SEM CD measurements were obtained, revealed small but significant test-chip-to-test-chip variability of the SEM-to-HRTEM offset at the low single-digit nanometer level. Further measurements made the case that this unanticipated variability originated in the differences in the amounts of hydrocarbon deposition that were made by the SEM tool during the measurement cycle. This is considered to be a very useful finding because modern SEM tools, which can reduce hydrocarbon deposition below levels that were encountered here by almost an order of magnitude, are now becoming available. The results reported here provide a strong indication that HRTEM-SEM-based calibration approaches offer great promise for single-digit nanometer uncertainty.     

Transient response analysis of a Rosen-type piezoelectric transformer and its applications

This paper investigates the characteristics of voltage transient response, such as the maximum voltage, direct current (DC) time constant, alternating current (AC) time constant and oscillation frequency, and their applications for a Rosen-type piezoelectric transformer (PT). The transient response is induced immediately after an AC voltage connected to the PT is switched off. For the applications, the maximum voltage is used to elucidate how to cause an electrical shock for users of the PT under open-circuit operation. The DC time constant and the AC time constant are used to estimate the equivalent resistance of the mechanical loss and the dielectric resistance of the dielectric loss, respectively. Also, the AC time constant is used to estimate the quality factor of the PT. Additionally, the oscillation frequency is used as an antiresonant frequency of the PT. In order to verify the above characteristics and applications, both an equivalent circuit with initial conditions and a drive system with a control switch interposed between the PT and its AC voltage source are adopted to derive the transient response and measure its characteristics. Effects of the load resistance of the PT and the switching-off time of the voltage source on the transient response are measured and discussed.     

Development of thin-film multijunction thermal converters atPTB/IPHT

The thin-film multijunction thermal converter (PMJTC) developed in cooperation between Physikalisch-Technische Bundesanstalt (PTB) and Institut fur Physikalische Hochtechnologie e.V. (IPHT) is today's most sensitive and accurate standard for the precise measurement of electrical AC quantities in the frequency range of 10 Hz-1 MHz. Thin-film technology and micromechanics in silicon were essential for this success. The thin-film heater and bismuth/antimony thermocouples with high Seebeck effect deposited on a thin membrane of low heat conductance result in the attractively high sensitivity of the PMJTC which allows voltage measurements down to 100 mV to be performed. The statistics of the mass production of the PMJTCs show that PMJTCs built into a housing with an N-connector at the input can be reproducebly manufactured with an AC-DC voltage transfer difference smaller than 0.1 μV/V at 1 kHz, 8 μV/V up to 100 kHz, and below 40 μV/V up to 1 MHz for a heater resistance of 90 Ω. A compensation circuit has been added on the chip which results in low-frequency PMJTCs (LF-PMJTCs) with AC-DC transfer differences below 0.3 μV/V at 10 Hz