Assessment of the uncertainty associated with synchronization error in analog to digital conversion with dither and CAV

Anna Domanska

Abstract

The paper discusses the problem of cumulative averaging (CAV) of digital signals after the analog to digital conversion with dither signal. The CAV algorithm performs three operations: division of the signal into a set of repetitions, synchronization of sectors of each repetition and cophasal averaging of samples. The influence of non-ideal synchronization of digital sectors on the value of samples of signal being a result of CAV was assessed. A dependence determining the variance of the signal value after averaging was given because of synchronization error. In the case of sinusoidal signal, the variation depends on: synchronization error variance, signal amplitude, relation between signal frequency and sampling frequency, and the number of signals averaged. With non-zero synchronization error, CAV – reducing additive noise – causes distortions in actual values of signal being a result of averaging, and increases the uncertainty value of such a-d conversion result.

Keywords

a-d conversion, dither, synchonous digital averaging

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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