din engleză în română Tehnică/Inginerie Altul military

Instead of only one pulse, a train of echoes is received. If the wall thicknesses are small (6 mm and less) this may cause the echo patterns from the front and rear walls to blend together. To avoid erroneous measurements, the closing of the measuring gate for wall thickness measurements is prevented for a measurement blocking period 9. This aperture is set to about 1.7 .mu.s, which corresponds to a wall thickness of 6 mm. Smaller wall thicknesses can thus not be detected. Rather, it may happen that directly after the expiration of the measurement blocking period 9, the ***broadened echo*** signal from a rough surface still lies above the triggering threshold and thus stops the counter. This then leads to a detection of the measurement blocking period as a measure for the wall thickness 8.

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