Fig. 4 shows echoes calculated, by using the model of
Fig. 3, for the driving conditions of Fig. 2, in the case of
a normal reflection through water from a plain steel
target situated in the near field of the transducer. The
negative effects on the echo signal of removing the rec-
tifier sets RÃ can be clearly seen, in comparison to the
C
echo where the direct effect of RÃ prevents the length-
C
ening of the echoes. Without RÃ the echo amplitude had
C
been reduced near to the half value and the signal length
had notably increased, which is very harmful for NDE
purposes. Therefore these non-linear effects from driver
devices, RI and RII , bring advantages as regards the
CC
bandwidth and the echo amplitude, and should not be
ignored in any modelling process.