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In particular an optimization of:
Digital ultrasonic instruments have been in use for some time as components of NPP inspection. So far, guidelines and standards have not contained characterizations of signal recognition or evaluation, as long as the Digitization has been applied for gate (monitor) techniques only. That means there is no documentation concerning the Digitization of ultrasonic echo signals in DIN 54119 (08/1981) "Ultrasonic Testing - Terms (Ultraschallprüfung - Begriffe)" and DIN 25450 (09/1990) "Ultrasonic Test Systems for Manual Testing (Ultraschallprüfsysteme für die manuelle Prüfung)".
Only in DIN 25435-1 is it mentioned that the resolution must be equal to or greater than 1 dB if analog to digital conversion is applied (DIN 25435-1 [11/1987] "Wiederkehrende Prüfungen der Komponenten des Primärkreises von Leichtwasserreaktoren - Mechanisierte Ultraschallprüfung"). For our interpretation a limit of the quantifying error is determined and in particular the applicable echo dynamic range is limited (e.g., for a 8 Bit A/D converter approx. 20 dB).
In ultrasonic testing procedures for defect description certain methods are used which cannot be detailed within the framework of a guideline stipulation. Nevertheless, standards of inspection procedures and instruments must be applied for defect detection, to ensure repeatability and comparison with previous inspections. This must also be a consideration when digital ultrasonic instruments are used.
Therefore, in new or modified ultrasonic testing standards it is necessary to include and define applicable terms, as well to define the characterization of ultrasonic instruments, such as A/D converters, sampling error, sampling frequency, data recognition and reduction, evaluation procedure, etc.
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