What is difference between rms error, peak error, and p-p error?
If one assumes a series of measurements of the actual position of the positioner versus the commanded position, for each measurement the error is the difference between the measured and the commanded position. The peak error is the maximum value of this error, taking into account that this error can also be negative. The p-p error (peak to peak error) is the difference between the maximum positive error and the maximum negative error. The RMS (root mean square) error takes the whole series of errors, squares them (‘calculating the energy in the error’) takes the mean of those values (‘determining the average energy’) and take the root. NSI defines its planarity and positioning error in terms of RMS. This gives more information on the overall performance since RMS takes all measured errors into account, as opposed to the peak error or p-p error that depends basically on a single coincidental value.
