Which device is a mini version used for ultrasonic testing?

Answer: A — meter

The D-meter is considered a mini version used for ultrasonic testing. This device is specifically designed to measure the thickness of materials, which can be particularly useful in assessing the integrity of bridge components and other structures. The D-meter operates on the principle of ultrasonic testing by sending sound waves into a material and measuring the time it takes for the waves to reflect back, allowing for the evaluation of thickness and the detection of flaws or corrosion. Ultrasonic testing is a widely used non-destructive testing (NDT) method that ensures the safety and reliability of structures by identifying internal and surface discontinuities. The portability and ease of use of the D-meter make it suitable for field inspections, enabling inspectors to take quick measurements without needing bulky equipment. In contrast, the other devices listed have different testing principles or applications; for example, a radiographic unit uses X-rays or gamma rays to view the internal structure of materials rather than focusing on thickness measurements. Therefore, the D-meter is the most accurate choice for a miniaturized ultrasonic testing device.