On the measurement of phase angles between sinusoidal signals of very low frequencies
Hans J. Goettler, Craig W. Nelson · Journal of Physics E Scientific Instruments · 1971
Two methods are discussed which can be employed individually or in combination to reduce two sets of data points representing sinusoidal signals of equal, and very low, frequencies. The phase angle between the signals as well as their amplitudes and average values can be determined. One method is based on a least squares analysis, the other utilizes the geometrical properties of the Lissajous figure obtained from the sets, when combined in one coordinate system.