The paper presents research on the capability of the residual magnetic field (RMF) measurement system to be applied to the railway inspection for the early non-destructive detection of defects. The metal magnetic memory (MMM) phenomena are analysed using normal component Hy of self-magnetic flux leakage (SMFL), and its tangential component Hx, as well as their respective gradients. The measurement apparatus is described together with possible factors that may affect the results of measurement. The Type A uncertainty estimation and repeatability tests were performed. The results demonstrate that the system may be successfully applied to detection of head check flaws.
A metrological verification of a high precision digital multimeter was made by the laboratory of calibration of programmable electrical multifunction instruments of the National Institute of Metrological Research (INRIM) in order to verify its accuracy and stability. The instrument had been tested for a period of six months for five low-frequency electrical quantities (DC and AC Voltage and Current and DC Resistance). Its stability and precision were compared with the accuracy specifications of the manufacturer. As a new approach, a performance index of the DMM was introduced and evaluated for each examined measurement point. The DMM showed a satisfactory agreement with its specifications to be considered at the level of other top-class DMMs and even better in some measurements points.