Root Mean squared Deviation (RMSD)
In EMI technique, change in the admittance signatures reflects the damage in the structure. The horizontal or vertical shift in the signature or the appearance of new peaks or reduction of old peaks are the key indicators of the damage. To calculate the deviation in the admittance signature, RMSD is used which is common in SHM. Giurgiutiu and Rogers in 1999 defined the RMSD index as where 鹿Gj is the conductance after the damage at a jth frequency and 鈦癎j is the conductance at pristine state at the same jth frequency respectively.

CC INDEX
CC index was used for the repeatability of the admittance signatures in this thesis which is given as where xi is the conductance of the signature-I and 饾懄饾憱 is the conductance reading of the signature- II at the same frequency respectively. 饾湈饾懃 and 饾懃虆 are the standard deviation and mean of signature- I respectively and 饾湈y and 饾懄虆 are the standard deviation and mean of signature-II.