PAUT data file size

An encoded phased array scan stores a complete A-scan for every law at every position. The size is therefore samples × bytes per sample × laws × positions × groups. Samples come from the digitising frequency and the time the displayed range represents: 2 × range / c microseconds multiplied by the sampling rate in MHz.

The numbers get large quickly. A 100 mm shear range digitised at 100 MHz is about 6200 samples per A-scan; multiply by 101 laws and by 1001 positions along a metre of weld and the raw volume is over half a gigabyte for a single pass at 8 bit resolution.

The levers are the same ones that govern frame rate. Trim the displayed range to what is actually being inspected, reduce the digitising frequency to the usual four to ten times the probe frequency, use 8 bit storage unless the procedure requires more, and do not carry redundant laws. Where the instrument offers averaging of the stored A-scan or compression, the saving is real but so is the loss of raw data for re-analysis.

samples = (2 × range / c) × f_s
positions = scan length / scan resolution + 1
bytes = samples × bytes/sample × laws × positions × groups