Dependency of signal to noise ratio on transducer diameter and buffer diameter in guided wave time domain reflectometry

The use of waveguides or buffer rods (BR) is well known in performing Non-Destructive Testing (NDT) with ultrasonic or generally in high-temperature ultrasonic time domain reflectometry (TDR). However, determining optimal geometrical shapes of these buffers and parameters of the ultrasonic transducers are not straightforward. In this paper the signal to noise ratio (SNR) achieved with different combinations of buffer diameters and transducer diameters are considered based mainly on experiments and on some dedicated simulations. Experimental results show large variations of the SNR as the ratio between the transducer and the buffer rod diameter varies. Corresponding simulated results are less influenced by such variations in the ratio of diameters considered, showing possible limitations of these simulations.