Forum Technical Discussions Ultrasonic A-Scan interpretation Posted by: Philippe Rubbers (PID_168), E-mail: Address, on June 12, 2008 at 09:18 : Dear colleagues There are 2 approaches for setting the range on an A-Scan: 1) at the position of the peak amplitude. 2) at 10% of the peak amplitude on the leading edge (flank). Historically (for very narrow bandwidth probes) with long ring down times, this 10% story makes a bit of sence, as the peak is not always evident. However in this day and age, this is no longer an issue, and the peak is the correct mathematical location of the reflector (can be proven with broadband probes and CSSP, as all frequencies are in phase at the peak). Since beam skew will give longer measured ranges, an error in the shorter direction is also beneficial (statistically) if the operator does not have the correct wedge angle or does not maximise as he should. If the gain is then changed, the range for the '10%' setting will change as the leading edge will come closer. Now comes the question: In phased array images, the overlay is nearly always placed at the 10% location. To me this is incorrect... Why is this done? Best regards Follow Ups: Re: Ultrasonic A-Scan interpretation Ed Ginzel 10:09 Jun-12-2008 (1) Re: Ultrasonic A-Scan interpretation mustafa GONULAL 11:10 Jun-12-2008 (0) Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : Dear colleagues : There are 2 approaches for setting the range on an A-Scan: : 1) at the position of the peak amplitude. : 2) at 10% of the peak amplitude on the leading edge (flank). : Historically (for very narrow bandwidth probes) with long ring down times, this 10% story makes a bit of sence, as the peak is not always evident. However in this day and age, this is no longer an issue, and the peak is the correct mathematical location of the reflector (can be proven with broadband probes and CSSP, as all frequencies are in phase at the peak). Since beam skew will give longer measured ranges, an error in the shorter direction is also beneficial (statistically) if the operator does not have the correct wedge angle or does not maximise as he should. : If the gain is then changed, the range for the '10%' setting will change as the leading edge will come closer. : Now comes the question: : In phased array images, the overlay is nearly always placed at the 10% location. To me this is incorrect... : Why is this done? : Best regards ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help