A Signal Processing Method for Steel Plate Thickness Measurement Using EMATs

Abstract

The time-of-flight (TOF) of the electromagnetic acoustic transducer (EMAT) echo signal can be used to measure the steel plate thickness. There are two ways to obtain the TOF, which are measure the peak to peak time in the time domain and calculate the echo frequency in the frequency domain. In this paper, a simplified signal model is proposed based on the analysis of received signals. Further, the relationship between the echo signal and excitation signal is considered. The echo signal is separated when the asynchronous demodulation method is applied to the received signal, and the thickness of steel plate can be calculated according to the peak spectral frequency in the low frequency band. The simplified model and signal processing method are verified by the experiment, and the results show that the model is reasonable and the accuracy of the signal processing method is high.