A novel measurement method and a brief discussion of basic characteristics of measuring the phase shift angle between two sinusoidal signals of the same frequency are presented in this paper. It contains a mathematical model for using conditional averaging of a delayed signal interfered with noise to measure the phase shift angle. It also provides characteristics of conditional mean values and discusses the effect of random interferences on the accuracy of the phase shift measurement. The way to determine the variance of the conditional mean value, together with the assessment of standard and expanded uncertainty, are described. The uncertainty characteristic shows the complementary properties of the discussed angle measurement principle �� for small absolute values |��| (minimum for �� = 0) relative to the correlation principle, where the minimum measurement uncertainty is present for �� = ��/2. |