A couple of years ago I&M Magazine published an article entitled Pure and Applied Metrology [1]. It described work done making a measurement of some parameters in the electric power system, parameters that were the coefficients of terms in a not very complicated equation that described the way the signals in the power system varied. That equation was a model of the way the signals in the real world behaved, but it was a simplified one, because the real signals generally included harmonics, random noise, low-frequency components and even non-harmonically-related signals.

10aAA14-0011 aKirkham, Harold1 aWhite, Rod uhttps://ieeexplore.ieee.org/document/8573595/http://xplorestaging.ieee.org/ielx7/5289/8573578/08573595.pdf?arnumber=8573595