“…SPM, developed by SPM instrument AB Company in the early 1970s and originated in Sweden, is a patented technique and has achieved wide acceptance as a quantitative method for efficiently inspecting the condition of bearings [6,12]. Through sampling the shock pulse amplitude of bearings over a period of time and displaying the maximum value dB m and the carpet value dB c , SPM provides a direct normalized shock value indicating the bearing operating state and lubrication condition [7].…”