Research And Implementation Of High-Precision Wideband Power Measurement System Based On Embedded Digitizer

With the requirement of the military, medical, and other magnetic materials of applications in high-frequency, the traceability is urgent need for power with frequencies below 100KHz. Currently the datum of broadband power measurement was established by the Chinese National Institute of Metrology in 1982, has been unable to meet the national broadband power traceability and calibration requirements. In order to accurately calibrate and traceability the broadband power, our country and abroad using a variety of methods, including thermoelectric comparison, binomial square method, three-parameter method, the current comparator and digital sampling method. With the development of AD sampling techniques, the using of sampling methods have been more and more frequently applied in the field of the electromagnetic measurement.Broadband high-precision power measurement system mainly consists by a broadband signal source, a voltage proportional divider, a current shunt and a broadband sampling board. The main content of this thesis is to assess the two simultaneous broadband voltage sources, using a software algorithm for the inadequate performance of the sampling board, the dual-channel voltage signal acquisition realization sampling performance evaluation boards and software algorithms assessment.For a detailed study to a dual-channel broadband voltage source with analysis, implementation and performance comparison is studied with several methods, including dual synchronization DA output method, two single voltage source of precision using external synchronization output method and high precision dual-channel synchronization phase source output method.Taking into account the high precision and the wide spectrum is required of the power measurement, and not only optimizing the hardware but also the software with the algorithm as much as possible. In order to solve leakage problems caused by the sampling rate is not high enough relative to the harmonic energy of the sampling frequency of the signal, using a non-integer periodic sampling and the appropriate compensation algorithm. At the same time determined the relationship between the phase and amplitude uncertainty in the sampling.Due to the current use of the NI PXI-5922 embedded board is highly integrated, expensive and other reasons, consider using an independent embedded development board SEED-DEC 138 achieve dual-channel synchronization signal voltage measurement function. DEC 138 is a high-performance DSP+ARM dual-core processor, consider using DSPLINK for dual-core communication and the ARM core in charge of interrupt control, interface display and other functions, the DSP core mainly for high-speed high-precision calculations, giving full play to the DSP core and the ARM core performance. Taking advantage of the most advanced technology EDMA3 ping-pong cache, the sampling chip can transfer sampled data directly without CPU processing, full use of DSP and ARM dual-core to their strengths to work together to make the embedded board to play to the best performance. Although because of the larger the sampling channel noise and other reasons, the sampling chip board resolution is not high, and the DEC138 embedded board on sampling performance can’t meet the requirements, but from the actual measurement situation, as long as the swap overcome these factors, the use of independent embedded board to achieve this sampling measurement method is feasible.Finally, a more detailed analysis for the performance of the NI PXI-5922 digitizer, including assessment of the amplitude-frequency characteristics, phase-frequency characteristics evaluation of the amplitude and phase consistency and stability assessment of the dual-channel and others aspects. Experimental results show that the sample card PXI-5922 can well meet the needs of broadband power sampling.