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972 views
00:32 Feb-12-2008
Erik Mischker
UT waveform preference

Was wondering what is the common preference for people out there to view there UT waveforms in an A-Scan; full waveform, positive rectification, negative rectification, or full rectification. On my Krautkramer field unit, it defaults to negative rec. and on lab the instruments its full waveform. Is it just a personal preference for what one is use to looking at, or is there a benefit to one or the other? Thanks


 
01:06 Feb-12-2008

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
Re: UT waveform preference Some of it has to do with customary practice, and some with test requirements.

Full wave rectification is most people's choice for common flaw detection applications with portable instruments and narrowband transducers (like most angle beam assemblies), in part because for many years in the pre-digital age that was all that portable flaw detectors offered and it became customary, and in part because it's a simpler presentation. However RF provides a more detailed picture of the wave shape that is usually required for interpretation in TOFD testing or phase-sensitive bond testing, as well as in precision thickness gaging applications with broadband transducers where consistent echo lobe detection is required for maximum accuracy.

Oscilloscopes and PC-based waveform digitizers typically offer RF waveforms because historically a lot of users of that type of equipment were doing precision time measurements and/or more advanced wave analysis.

As with most ultrasonic tests, the rule is to choose the approach that meets your needs!




 
01:34 Feb-12-2008

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
509
Re: UT waveform preference I would agree with Tom's comments entirely, in addition some people prefer to use one or other of the half wave modes for precision thickness and similar applications

I suspect that this is mostly historic - I've never found an application where it gives better results than RF, but a lot of operators seem to feel more comfortable with the unipolar presentation.

Joe

----------- Start Original Message -----------
: Some of it has to do with customary practice, and some with test requirements.
: Full wave rectification is most people's choice for common flaw detection applications with portable instruments and narrowband transducers (like most angle beam assemblies), in part because for many years in the pre-digital age that was all that portable flaw detectors offered and it became customary, and in part because it's a simpler presentation. However RF provides a more detailed picture of the wave shape that is usually required for interpretation in TOFD testing or phase-sensitive bond testing, as well as in precision thickness gaging applications with broadband transducers where consistent echo lobe detection is required for maximum accuracy.
: Oscilloscopes and PC-based waveform digitizers typically offer RF waveforms because historically a lot of users of that type of equipment were doing precision time measurements and/or more advanced wave analysis.
: As with most ultrasonic tests, the rule is to choose the approach that meets your needs!
------------ End Original Message ------------




 


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