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Agilent 3458A digital multimeter in the harmonic measurement


Signal sampling in, will be confused by the sampled signal, affect the analysis of the sampled signal accuracy. To avoid this effect, the sampling rate must satisfy the Shannon sampling 34 * law. If the sampling rate is greater than. Frequency of 5 times to 10 times, FFT computation result of the error will be smaller. 2) The frequency resolution is the frequency resolution can signal the algorithm used in the two spectral peaks are very close to the ability to keep separate. If the signal under the (t) of length T seconds, after sampling with a sampling interval becomes (), that is, sampling frequency = 1 /. So, T-second under the (t) can be M = T / point. Can also be regarded as infinitely long discrete signal (, z) and a rectangular window of width M multiply result. Then, the signal for the fast Fourier transform, the frequency resolution is Af = fs, M is in the use of fast Fourier transform rectangular window that can tell when the minimum frequency interval. Obviously, if Af small enough, you can not distinguish two adjacent harmonics. 3) In most cases, synchronous sampling, synchronous sampling refers to the signal period is an integer multiple of sampling interval sampling state. For periodic signals, as in the actual testing and sampling is difficult to synchronize the signal,[link widoczny dla zalogowanych], making the truncated signal is not an integer multiple of cycle of periodic signals,[link widoczny dla zalogowanych], and in the FFT signal in the truncated periodic signal that is a cycle, this man-made the formation of a spectrum signal jump extra high frequency components, such high-frequency components in the original periodic signal is not available, the use of the harmonic measure of H will have measurement error. Figure 5. An I / one by one -, /, a _,[link widoczny dla zalogowanych], /, one by one, (fU Figure 5 cycle signal and sampled by the sampling of periodic signals synchronized harmonic analysis is a very important content, you can reference [5] related content. in fact contain an integer number of sampling points just signal cycle is difficult to achieve, at this time should not take some measures to reduce the impact of synchronous sampling, such as a sample number of signal periods, plus the window function, quasi-synchronous sampling method and software synchronization. 4 Conclusion As we focus on power quality, harmonic measurement and harmonic analysis for the calibration of our work has become a frequently encountered problem. This article describes ways to help give full play to the measurement institutions Ag-ilent3458A DMM's ability to use its digital capabilities, with the harmonic analysis software, you can expand the instrument's ability to address the problem of harmonic measurement and calibration, testing and accurate measurements in the measurement has a good prospect. Reference [1] HU Guang book. digital signal processing theory, algorithms and implementation. Beijing: Tsinghua University Press, 2003 [2] Zheng Junli should Kai Heng, Yang is management. Signals and Systems. Beijing: Higher Education Press, 2Oo0 [3 ] American Agilent .3458 A digital multimeter instruction manual. American Agilent, 1998 [4] GBZI \guidelines [5] Liang Zhiguo. Review of periodic signal harmonic analysis. Measurement Technology,[link widoczny dla zalogowanych], 2003 (2)-type water level sensor used NSC1.5 automatic water supply system design field CMC, 2 Bo Xiaotian 3 to jump deep (1. Xi'an University of Technology Electrical and Mechanical Engineering, Xi'an 710032, China; 2. Xi'an Jiaotong University, Institute of Electronic and Information Engineering, Xi'an 710049, China; 3. Xi'an Kunlun Industrial Group Co., Ltd., Xi'an 710043, China) Abstract The least square method used trailers carrying water level sensor calibration, was the water level and the voltage of the least squares equation, according to testing the structure of water level and water storage tanks for water tank derived formula,[link widoczny dla zalogowanych], from the calibration formula and the formula amount of water consistent with the actual test results. expounded trailer auto transport water The hardware structure of the water supply system and the key principles of the performance characteristics of the device and method of use of temperature detection part, the water level detection part of the control section and power supply part of water were introduced. of the system software components and work flow chart, the battery-powered procedures and automatic control program works for a more detailed analysis. The design has been successfully applied to the automatic water supply system carrying water trailer product. Keywords automatic water supply system; least squares; level detection; temperature detection; water calculation . One important part of logistics support. the traditional drinking water supply by setting u Si trailer storage equipment, supply, its water and water use of semi-artificial, half when the engineering team for construction in the field, the water supply auto mode , the control system test water level switch used to detect the amount of salt hit Mexico: * 35 *

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