Conventional ultrasonic probes

Three series: PL, PH and C

Doppler conventional probes come in three variants that differ in how the pulse behaves. That is the first decision, before frequency and diameter: a longer pulse means higher sensitivity and deeper penetration, a shorter one means better resolution just under the surface.

Construction to match the job

The second decision is the probe design. Welded joints are inspected with an angle beam probe on a wedge: the angle is chosen so the beam crosses the fusion face, and 45°, 60°, 70° and 90° are standard in steel. For thickness and corrosion a dual element (TR) probe is better — separate transmitter and receiver remove the initial pulse dead zone, so a thin wall is visible right below the surface.

For heavily attenuating materials and austenitic steel there are TRL angle probes, dual element longitudinal wave probes with focusing and a better signal-to-noise ratio. Where the part is very thin or the surface curved, a delay line probe takes over (2.25–20 MHz, 3–13 mm diameters). A separate group are normal incidence shear wave probes, used more for elastic modulus and grain structure work than for flaw detection.

Before you order

• Frequency: 1–2.25 MHz for attenuating materials, 3.5–5 MHz for ordinary welds, 7.5 MHz and above for thin walls and fine discontinuities
• Element size: Φ6, Φ10, Φ13, Φ25 mm plus 13 × 25 and 19 × 25 mm; the smallest special element is 3 × 4 mm
• Connector: Microdot (L5), Lemo 00 (C5) or Lemo 01 (C9) — it has to match the cable and the instrument socket, see Cables and connectors for flaw detectors
• Contact face: AID, CID, AOD or COD machining when the probe sits on a pipe or another curved surface
• Data sheet to the standard you work to: EN ISO 22232-2, ASTM E1065 or GB/T 27664.2