For the requirement of inspecting nonferrous metal strips

the injected direct current-magnetic field measurement（IDC-MFM） method is studied. This method realizes inspection for conductive materials by injecting direct current into the tested object to induce magnetic field and using high sensitivity magnetic sensing probe to detect the magnetic field change. According to the results of three-dimensional magnetic field simulation

the distribution characteristics of magnetic field surrounding the tested plate is analyzed when the plate has nondefect

convex defect and concave defect. At the same time

the variation characteristics of transverse magnetic flux density surrounding defect and the signal feature of defects are researched. The inspecting experiments for copper and aluminum strips samples are performed. The experimental results are consistent with the simulation

which indicates that IDC-MFM method has the capability of inspecting convex defects

concave defects

ridgy defects and marginal defects on nonferrous metal strips.