Measurement in AE System based TCM

The AE signal usually needs to be initially pre-amplified and then bandpass filtered

A high bandpass filter is used to reduce the influence of the low frequency noise, considered to be uncorrelated with the tool state

The AE signal is fed through a low bandpass filter to eliminate the high frequency noise components due to electric sparks and/or to avoid signal aliasing

The amplitude spectra consist of components only from the frequency range of interest

Among all the elements composing the measurement chain, the most important is the piezoelectric AE sensor