A special scanning device with the transducer mounted in a tire-like container filled with couplant is commonly called:

• A. Rotating scanner
• B. An axial scanner
• C. A wheel transducer
• D. A circular scanner

Answer: (C)

In ultrasonic testing, a transducer housed in a tire-like shell filled with couplant that rolls along the surface is called a wheel transducer. The tire-shaped chamber keeps the transducer in constant acoustic contact as it rolls, allowing continuous scanning around circular or curved surfaces like pipes or welds. This setup is more specific than a general rotating scanner, and it isn’t typically described as an axial or circular scanner. The wheel transducer design is chosen precisely because it provides steady coupling and smooth, rolling motion for circumferential inspection.