Phased array probes (PAUT)

The series and the jobs they were built for

A phased array probe is a row of individually pulsed elements. By controlling the delays, the instrument steers and focuses the beam without moving the probe — one pass instead of several. Doppler builds them from 0.5 to 20 MHz, with 8 to 1024 elements and a 0.2–2.0 mm pitch, in linear, matrix, annular, concave and convex layouts.

Pitch, aperture and element count

Pitch, the distance between element centres, limits how far the beam can be steered before grating lobes appear — the working rule keeps it below half a wavelength, which at 5 MHz in steel lands around 0.5–0.6 mm. The active aperture, element count times pitch, decides how deep the beam can be focused: a small aperture focuses shallow and diverges quickly.

So a 32-element probe with a fine pitch makes sense on thin sections, while thick walls and deep focusing call for 64 elements or more. Doppler probes hold sensitivity within ±2 dB, batch to batch as well, which matters when a worn probe is replaced mid-contract: the procedure does not have to be rewritten.