Measurement, Nyquist and Shannon: A view of PMU metrology

It is generally understood that in a (digital) measuring system, attention must be paid to the criterion usually identified with the name Nyquist. The paper shows that there is no such a priori requirement. The observations of Nyquist are examined: some may seem unfamiliar. Sampling and measurement are described as different activities in the quest of information retrieval. A link to Information Theory is discussed.