This ultrasonic instrument is designed to characterise the quality of Spheroidal Graphite iron. The measuring principle is based on the propagation of ultrasound in the material. If the micro structure of SG Iron is not of the desired quality, the nodularity count is insufficient and the percentage of graphite flake increases. The quality deficiency is associated with a decreased elastic modules and a drop in the average velocity of ultrasound.

This instrument is capable of measuring the ultrasonic velocity accurately. From this velocity, we can judge the percentage of nodularity.