This part of ISO 20283 provides guidelines for the instrumentation, measurement and data processing procedures to obtain reliable vibration data on ship propulsion systems. It gives guidance for the application of specific measuring techniques, which are common and adequate for measuring the mechanical vibration on propulsion plants of sea-going and inland vessels. The measuring techniques can be applied to diesel engine as well as turbine or electrically driven plants, always considering the specific limitation of application of each individually described procedure. The procedures described in this part of ISO 20283 are focusing on repetitive mechanical vibration (steady state or quasi-stationary like a sweep) and may therefore be inadequate for measuring and evaluating transient, very fast changing or shock signals. This part of ISO 20283 mainly describes measuring techniques to be applied for measuring the mechanical vibration of the main propulsion plant during sea trials. Same or similar measuring principles can also be used for other purposes, such as performance monitoring, investigations of abnormal vibration in service, and evaluation of repaired parts condition. However, in such cases the measuring procedure needs to be adapted to the specific requirements.