共查询到20条相似文献,搜索用时 31 毫秒
1.
为了解决在应变测量中需要的高精度、低干扰并具有相对大的驱动能力的激励源产生的问题。采用可编程基准源和驱动两级电路,通过可编程的DAC生成电压基准,再通过驱动电路,程控选择电压激励源和电流激励源的生成和输出。所设计的程控精密激励源具有体积小、精度高、功耗低、配置灵活的特点。实际应用表明,本设计达到了技术方案要求并已成功应用于实际的应变测量之中。 相似文献
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《IEEE transactions on instrumentation and measurement》1968,17(3):177-185
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. 相似文献
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为实现高精度、高稳定的微小振动测量,设计了一种改进型迈克尔逊干涉仪,对其所采用的光学结构和解调算法进行了分析.信号解调方案基于载波调制和交流相位跟踪(ACPT)技术,相对应的光路采用双压电陶瓷(PZT)和准平面猫眼动镜以构成参考臂和测量臂,设计以改善信噪比、抑制低频干扰、增强系统稳定性、提高测量分辨力为目标.建立了纳米振动发生装置,搭建了振动信号测量系统,研究了激光干涉仪对振动信号的输出特性.实验结果表明,测量动态范围达到120 dB,信噪比高于40 dB,系统分辨力达到0.25 nm.该干涉仪可有效抑制诸如温度、湿度、压强、低频振动等带来的相位噪声的干扰,满足高精度、稳定、可靠的要求. 相似文献
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Kyynarainen J. Oja A.S. Seppa H. 《IEEE transactions on instrumentation and measurement》2001,50(6):1499-1503
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 相似文献
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Ciofi C. De Marinis M. Neri B. 《IEEE transactions on instrumentation and measurement》1997,46(4):789-793
The design, realization, and test of a multichannel ultralow-noise data acquisition system are described in this paper. The instrument, controlled by a personal computer (PC), has been specifically designed for performing low-frequency noise measurements on interconnect lines of an integrated circuits. A specifically designed ultralow-noise preamplifier has been realized and an optical link has been used for connecting the front-end of the instrument with the PC in order to minimize the effects of electromagnetic interferences. An overall background noise some orders of magnitude below that of preexisting instrumentation has been obtained. In particular, the power spectral density of the equivalent input voltage noise was 1.5, 3, 10 nV/(Hz)1/2 at 1, 0.1, and 0.01 Hz, respectively 相似文献
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《IEEE transactions on instrumentation and measurement》1978,27(4):372-376
In order to complete an automatic system for EMF comparison of standard cells in a reference group, an automatic potentiometer at nanovolt level was implemented. However, the equipment can be dedicated for general purpose measurements of dc voltages lower than 1 V. The system reproduces the techniques of manual potentiometers opposing the unknown voltage against a compensation voltage. Starting from the unbalance signal of a galvanometric photocell amplifier, a microcomputer provides a suitable strategy of null balance, acting on the compensation source and the galvanometer sensitivity. In this way, the current in the measuring circuit is continuously kept at an almost zero value. With respect to manual potentiometers, this apparatus does not require an operator and reduces the measurement time. The period of a measurement cycle depends on the present noise level and the number of successive balances. A time of about 2 min is typical for a peak noise of 1 nV. 相似文献
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Antti Laitinen Manohar Kumar Teemu Elo Ying Liu T. S. Abhilash Pertti J. Hakonen 《Journal of Low Temperature Physics》2018,191(5-6):272-287
We have investigated the cross-over from Zener tunneling of single charge carriers to avalanche type of bunched electron transport in a suspended graphene Corbino disk in the zeroth Landau level. At low bias, we find a tunneling current that follows the gyrotropic Zener tunneling behavior. At larger bias, we find an avalanche type of transport that sets in at a smaller current the larger the magnetic field is. The low-frequency noise indicates strong bunching of the electrons in the avalanches. On the basis of the measured low-frequency switching noise power, we deduce the characteristic switching rates of the avalanche sequence. The simultaneous microwave shot noise measurement also reveals intrinsic correlations within the avalanche pulses and indicate a decrease in correlations with increasing bias. 相似文献
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Lanoue E. Genest J. Gibeault M. 《IEEE transactions on instrumentation and measurement》2006,55(3):860-868
Many noise sources deteriorate the performance of a Fourier-transform spectrometer. When such an instrument utilizes a reference source such as an HeNe laser to sample the measurement data, it is desirable to determine how the intensity fluctuations of the reference source will affect the final spectrum. This text shows how the intensity noise of the reference laser is transformed at the output of the interferometer, how it translates into a sampling jitter by a simple linear relation under a small bandwidth approximation, and how it is manifested in the final spectrum as a noise floor. Analytical and simulation results show that for an instrument designed for optical communication applications, the intensity noise of the reference laser may be one of the dominant noise source limiting the overall performance of the instrument. 相似文献
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Piezoelectric tube actuators are widely used in atomic force and scanning tunneling microscopy (STM) for nanoscale positioning. There has been a consistent effort to increase the scan speed of these actuators using feedback control techniques. A feedback controller requires a measurement of the scanner's deflection, which is often provided by a capacitive sensor. Such measurements are corrupted by sensor noise, typically in the order of 20 pm/ radicHz rms. Over a bandwidth of 10 kHz, this translates into an rms noise of 2 nm, clearly inadequate for applications that require subnanometer positioning accuracy, e.g., STM. In this paper, we illustrate how the strain voltage induced in a free electrode of the scanner can be used as an additional displacement signal. The noise level corresponding to the strain signal is about three orders of magnitude less than that of a capacitive sensor, making it an ideal choice for nanopositioning applications. However, it cannot be used for dc and low-frequency measurements. A two-sensor-based controller is designed to use the capacitive sensor signal at low frequencies, and the strain displacement signal at high frequencies. By limiting the capacitive sensor feedback loop bandwidth to less than 100 Hz, the rms value of the noise is reduced to well below 1 nm. For almost the same noise level, the two-sensor-based control structure achieves a closed-loop bandwidth of more than three times that of the single-sensor-based controller. 相似文献
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Design and calibration of a noise measurement system 总被引:3,自引:0,他引:3
Chun-Yu Chen Chieh-Hsiun Kuan 《IEEE transactions on instrumentation and measurement》2000,49(1):77-82
The setup principle and calibration method of a noise measurement system for frequencies from dc to 10 kHz are described. This system measures the current noise power spectral density of some device, and consists of a low-noise current preamplifier, a voltage preamplifier, and a dynamic signal analyzer which implements the fast Fourier transform (FFT). The noise aspects of the whole system can be modeled as a serial noise voltage generator and a parallel noise current generator at the input port, plus a system free of noise. The cross correlation of the two noise generators is an imaginary number because the system input stage is composed of some junction field effect transistors (JFET's). Via the thermal noise measurement of several resistors, we derive the magnitudes of the noise generators in addition to the input impedance and the total system gain. The imaginary cross correlation is obtained by the noise measurement of pure capacitance. With a well-calibrated procedure, we can measure the noise power down to 2×10-27 A2/Hz. Two systems with different input stages were calibrated with the same procedure and the noise measurement results of the various resistance values with the two systems all agree well with theoretical values. One of these with an input stage which has a much smaller noise current generator shows great improvement in the noise measurement of the high-impedance device 相似文献
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《IEEE transactions on instrumentation and measurement》1980,29(3):153-157
The design of an instrument for precision measurement of ac voltage, current, power, and energy is described. It has been developed as a standard for evaluating the performance of instrumentation used in the power frequency range (45-65 Hz). Its accuracy relies on a continuous ac/dc transfer which is achieved by automatically balancing the alternating current derived from the quantity to be measured against the equivalent direct current, both passing alternately through the heater of a thermal converter. Since the instrument can be calibrated with direct voltage and current, its total systematic error is limited by the ac/dc transfer to ±0.0005 percent of full scale for voltage and current, and ±0.001 percent of full scale for power and energy measurements. 相似文献
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Hala Mohamed Abdel Mageed 《Mapan》2011,26(4):329-337
A new automatic system for calibrating the solid state DC voltage reference standards (Zener Diode reference standards) has
been established at National Institute for Standards (NIS), Egypt to disseminate the unit of volt in the country. Besides,
this system has been implemented as a coherent structure that, from the national DC voltage reference standards, can disseminate
the traceability of all the instruments under calibration. The system consists of a set of programmable instruments and proper
software. The software of the system has been built using the Laboratory Virtual Instrument Engineering Workbench (LabVIEW)
graphical language. The system hardware is configurable by the operator on the basis of the specific calibration to be performed
and it allows large number and different models of Zener diodes to be act either as reference units or as units under calibration.
The design and the implementation of the system software have been discussed in details. Furthermore, the system validation
has been carried out for the measurement repeatability and the results compatibility in both automatic and manual modes. 相似文献
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《IEEE transactions on instrumentation and measurement》1967,16(3):187-191
Recent interest in accurate dc measurements down to nanovolt levels has prompted the development of a wide voltage range potentiometer of a new type with 7 dial resolution and extremely high accuracy. The potentiometer design is almost perfectly "neutral." All switch contacts and resistors of the main potentiometer operate at high voltage levels, and contribute thermal EMFs which are attenuated by a factor of ten thousand times (to less than 0.1 nanovolt levels) on the nanovolt range. The device serves as an "autocertified" voltage potentiometer standard. It is certified traceable to National Bureau of Standards units using previously published " ratiometric" techniques and is capable of direct reading accuracy without correction from 2 ppm on the 10-volt range to 10 ppm of setting ±1 nanovolt on the 0.001-volt range. The Thevenin equivalent source resistance of the instrument is approximately 2.5 ohms on the 0.001-volt range, reducing Johnson noise levels to less than 1 nanovolt with practical null detector smoothing times. The instrument is designed so that it can be used both as a potentiometer and as a 7-dial Kelvin-Varley divider. The control portion of the instrument is separately packaged and can convert dividers now in use to this new type of universal potentiometer standard. This paper includes a complete theoretical study of the design characteristics of this state of the art potentiometer, and an analysis of all sources of error in the completed instrument. 相似文献
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Optimized two-frequency phase-measuring-profilometry light-sensor temporal-noise sensitivity 总被引:1,自引:0,他引:1
Li J Hassebrook LG Guan C 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(1):106-115
Temporal frame-to-frame noise in multipattern structured light projection can significantly corrupt depth measurement repeatability. We present a rigorous stochastic analysis of phase-measuring-profilometry temporal noise as a function of the pattern parameters and the reconstruction coefficients. The analysis is used to optimize the two-frequency phase measurement technique. In phase-measuring profilometry, a sequence of phase-shifted sine-wave patterns is projected onto a surface. In two-frequency phase measurement, two sets of pattern sequences are used. The first, low-frequency set establishes a nonambiguous depth estimate, and the second, high-frequency set is unwrapped, based on the low-frequency estimate, to obtain an accurate depth estimate. If the second frequency is too low, then depth error is caused directly by temporal noise in the phase measurement. If the second frequency is too high, temporal noise triggers ambiguous unwrapping, resulting in depth measurement error. We present a solution for finding the second frequency, where intensity noise variance is at its minimum. 相似文献
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