3.3 Digital Signal Processing

Most modern ultrasonic flaw detectors incorporate digital rather than analog signal processing. While some older analog instruments are still in use, microprocessor-based digital processing is now the industry standard for portable flaw detectors. Its major advantages include:

• Precision and repeatability of test setups, which can be stored for quick recall
• Stability of horizontal and vertical linearity (no drift with time or temperature)
• Digital precision in measurement of amplitude and depth/distance, including trigonometric calculations in angle beam testing
• Digital filtering can improve near surface resolution and signal-to-noise in high gain applications
• Waveform freeze, peak memory, and zoom functions for easier analysis
• Fast and reliable implementation of sizing techniques such as DAC, TVG, and DGS
• Datalogger software for storage of screen displays and measurements in internal memory or on removable storage cards
• USB interface for offloading test data to computers for storage and further analysis

The potential advantage of analog processing in some cases is faster screen refresh and/or data acquisition rates.

Pulser and Receiver Operation