The difficulties of achieving precision in the ultrasonic detection of discontinuities in cast steel pipes and weldings such as those used in the nuclear electric and similar industries are well known. This paper reports the experimental results obtained from a computerized mathematical model (based on Snell's Law) designed to improve the accuracy of the location of flaws or reflectant surfaces using the real data of the material under study, such as plate thickness, penetration depth inside the wedge, wedge angle, velocity inside the wedge, angle of entrance into the metal surface and total distance readout on a cathode ray tube. On the monitoring set there are sometimes two beams: one is vibrating and indicates the flaw or the reflectant surface, while the other is fixed.