The iterative method could be used for automatic accuracy improvement of a measurement system. In its application for analogto-digital converter (ADC) a quantization error represents a limitation for the correction process. Therefore, combination of correction methods is common for ADC error correction. Combination of the additive iterative method (AIM) with nonsubtractive dithering (ND) has been proposed for slow measurement based on ADC where errors could change in time. The principle of combination of both techniques is described in the paper. AIM is based on precise inverse element (IE). In the designed system the IE output signal is created by pulse width modulation and low-pass filtering. A technique similar to deterministic dithering is employed to achieve precise processing of signal from IE. Analysis of influence of stochastic dither upon the results of correction is performed with the aim to find optimal parameters of ND. Finally, dependency of the root mean squared error and error dispersion on the measured value is drawn to show how AIM corrects the nonlinear deterministic error but slightly increases system noise.

No abstract

Multiresolution quantization (MQ) is used in modern equipment designed for wideband spectrum measurements with high dynamic range. Such time-domain measurement systems significantly reduce measurement time. Only basic theoretical analyses of the possible influences of MQ on the fidelity of the measured spectrum have been performed until today. Therefore, the real contribution of the method to the quality of measurement should be clarified. In this paper, a new model of quantization noise is proposed for MQ. It was derived from a model of power spectral density previously used for uniform quantization. A system with two different quantization steps used for the quantization of harmonic input signal is considered. The model suitability for such conditions is proved by simulation and confronted with experimental results. Multiresolution measurements were acquired using a dual-channel data acquisition card and personal-computer postprocessing.

No abstract

No abstract