Hello C. Allen Weekley, Thank you for contacting National Instruments.
Will you please elaborate on what you mean by "RMS error calculation for the time axis?" Are you looking for the phase shift? When you subtract two waveforms, you are calculating the difference between two amplitudes at a given time. Do you now want to find the difference between two times at a given amplitude? Please respond with more information and I will try to help. Have a great day, Sean C. Applications Engineer National Instruments
