Couplant
Couplant is a liquid or gel medium placed between the probe and the workpiece to minimize the air gap and ensure efficient sound transmission.
Physico-chemical mechanism of action
A couplant creates a tight contact surface between the probe and the workpiece by filling the air gap. This improves sound transmission and leads to more precise measurement results.
Metallurgical relevance & risks in welding
Without a couplant, an air gap between the probe and the workpiece can occur, which impairs sound transmission and leads to inaccurate readings. This can cause misjudgments in the material or weld.
Workshop practice & action instructions
Ensure that the couplant is properly placed and the contact surface between probe and workpiece is tight. For metals with high surface roughness, use a strong couplant such as water or a special sound oil. For fine surfaces, a weaker couplant such as air may suffice.