The detection of cracks in spot welding is a major issue especially on-line. This paper deals with this topic using acoustic emission monitoring. It proposes an approach based on Shannon entropy with a novel criterion that allows increasing the detection sensitivity. A data-based model is built, coded and then applied on acoustic emission signals. The obtained crack detection results are satisfactory. The cracks are revealed using fluorescent dye penetrant, which enables validating the method. A flowchart of whole the proposed approach is described so that practitioners can benefit from the authors experience, towards successful implementation in laboratory as well as in production-line. The current approach is applied on resistance spot welding as a case of study, but it could be applicable in non-stationary environment such as other kinds of spot welding, and more hopefully for other manufacturing processes.