周期性信号采样中,等效采样利用较低采样频率的A/D转换实现高频周期信号的采集,一定程度上弥补欠采样测量精度低的缺陷.为了有效地提高高频测量中阻抗谱测量精度与稳定性,提出一种基于等效采样思想的均匀相位采样的阻抗谱测量方法.利用单片机共时钟基准的模/数转换器(digital to analog convertor,DAC)与数/模转换器(analog to digital conver-tor,ADC)模块,在完成激励信号产生、输入输出信号同步采集的基础上,合理设计激励信号频率、采集频率与信号重构方法,实现高频信号单周期内均匀相位分布的等效高频采样,同时为克服常规A/D转换速度条件下难以准确实现高频阻抗谱测量的问题提供了新思路.从误差假设与拟合算法的角度,理论上分析证明了该方法降低误差的原因.并通过两种等效电路模型的阻抗谱测量对比实验,表明该方法在所设计的20～100 kHz高频段上,阻抗测量精度与稳定性得到了显著的提高.
Improving the Measuring Accuracy of High-frequency Impedance Spectroscopy Based on Uniform-phase Sampling
In periodic signal sampling,equivalent sampling utilizes A/D conversion with lower sampling frequencies to collect high-frequency periodic signals,which to some extent compensates for the low measurement accuracy of undersampling.In order to effectively improve the accuracy and stability of impedance spectrum measurement in high-frequency measurement,a uniform phase sampling imped-ance spectrum measurement method based on the idea of equivalent sampling was proposed.By utilizing the DAC and ADC modules of a microcontroller with a common clock reference,based on the generation of excitation signals and synchronous acquisition of input and out-put signals,the excitation signal frequency,acquisition frequency,and signal reconstruction method were reasonably designed to achieve e-quivalent high-frequency sampling of uniform phase distribution in a single cycle of high-frequency signals.At the same time,a new approach is provided to overcome the problem of difficulty in accurately measuring high-frequency impedance spectrum under conventional A/D conver-sion speed conditions.From the perspective of error assumptions and fitting algorithms,theoretical analysis proves the reasons for the error reduction of the method.The comparison experiments of two equivalent circuit models of the impedance spectrum measurement.It is shown that the accuracy and stability of impedance measurement are significantly improved in the high frequency band of 20～100 kHz.
万方数据
维普
