The present invention defines an improved strain gauge and a method of using an electromagnetic acoustic transducer (EMAT) for monitoring stress and strain in an underlying workpiece. The gauge is provided with positioning pins for fixing the registration of the EMAT relative to the workpiece. The gauge is provided with a friction reducing means, such as a bearing or a wheel assembly, to minimize EMAT bottom contact surface area and thus unwanted frictional influences caused by deformation of the workpiece under the EMAT. An assembly for reliably positioning the EMAT gauge above a workpiece is also disclosed, in which the assembly comprises an actuating means which by a linkage mechanism lowers or raises at least the EMAT into position, further allowing access to the positioning pins for applying the necessary force to fix the position of the gauge relative to the workpiece.