26 The density of the Si substrate is 2,300 Kg/m3, its Poisson’s

26. The density of the Si substrate is 2,300 Kg/m3, its Poisson’s ratio is 0.27, and its Young’s modulus is 160 especially GPa. The time domain waveforms of the SAW signals obtained by piezoelectric LSAW and differential confocal LSAW detection techniques respectively are shown in Figure 1(a,b).Figure 1.Time domain waveforms of the SAW signals obtained by (a) piezoelectric LSAW detection technique and (b) differential confocal LSAW detection technique.By comparing Figure 1(a,b), it can be seen that the SAW signal detected by piezoelectric LSAW detection technique has a larger amplitude, richer frequency components in general, but also has relatively significant noise amplitudes. On the other hand, the SAW signal obtained by the differential Inhibitors,Modulators,Libraries confocal LSAW detection technique shows weaker SAW signals, less frequency components, but lower noise relative amplitudes.
Figure 2(a,b) obtained as the Fast Fourier Transform of the data in Figure 1, shows the normalized amplitude spectra of the signals in Figure 1, from where the measurement bandwidth of the SAW signals can be visualized directly.Figure 2.Normalized amplitude spectra of SAW signals of the piezoelectric LSAW and differ
Since its discovery in 1988 [1,2] the giant magneto Inhibitors,Modulators,Libraries resistance (GMR) effect has been intensively investigated. This led, e.g., to a major boost Inhibitors,Modulators,Libraries in computer hard drive technology by means of smaller read heads resulting in an enhanced bit density. Generally, nowadays the GMR is of interest for many other applications concerning the determination of magnetic fields due to its resistance change of Inhibitors,Modulators,Libraries 10�C20% at room temperature, its remarkable field sensitivity and detection limit down to the pT-range [3�C5].
GMR sensors are prevalent in many different measurement applications such as proximity, position, rotational speed, angle, and GSK-3 electrical current. They can be easily miniaturized and their low power consumption is a further promising feature. Even though they are still relatively costly compared to their semiconducting counterpart��the Hall sensor��the GMR continuously claims further segments in the market, such as automation and production processes, automotive, cell phones, medical application and safety inspection. The latter includes all kind of electromagnetic testing methods to test the integrity of a component.
Here, the trend inhibitor bulk is driven by growing safety requirements in which industries call for reliable non-destructive testing (NDT) methods, especially when it comes to detect small surface breaking defects in the ��m-range. In recent years, GMR sensors have been intensively used as magnetic field sensors in magnetic flux leakage (MFL) [6,7] and in eddy current (EC) testing [8�C12]. Due to their main promising properties-the high field sensitivity and the high spatial resolution-also small defects can be quantitatively detected paving the way for automation of the testing process.

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