DescriptionUltrasonic receive signals are often close to the electronic noise floor and require high gain amplification before processing and display. Despite Electromagnetic Compatibility Standards, high levels of electrical interference are common in the manufacturing environments where NDT inspections are performed, and this can limit the detection of small reflected signals. Electronic filtering can help but is ineffective where the interference overlaps the ultrasonic transducer bandwidth, such as from motors.
Signal averaging can reduce the interference amplitude by a factor equal to the number of averages. However, this approach degrades the potential noise floor because the number of interference bursts in the resulting signal is increased by the same factor. Synchronizing the acquisition to the periods between interference bursts is possible where the source is known, but this is not simple and does not work for multiple sources. It is also inappropriate for automated inspection systems, where the acquisition time is related to inspection position.
A novel approach has been developed on the AWESIM (Advanced Welding Equipment System Inspection & Monitoring) Project to address this issue for in-process inspection whilst welding. The patent pending technique uses a modified acquisition sequence followed by matched signal processing, and can handle both asynchronous scanning and multiple sources of interference. The technique is equally applicable to rectified, RF and FMC acquisition modes, and even offers Signal-to-Noise Ratio (SNR) improvements for the samples where no interference bursts occurred. The paper will present results from automated data acquisition whilst welding, comparing “before” and “after” processing and shows that the developed technique is effective even where the interfering signal amplitude is greater than that of the echoes.
|Period||7 Sept 2022|
|Event title||NDT2022: 59th Annual British Conference on Non-Destructive Testing|
|Location||Telford, United Kingdom|
|Degree of Recognition||International|