The standard BS EN ISO 1 2058-1: 2018 Plastics, Viscosity Determination by Falling Ball Viscometer, Inclined Tube Method specifies a test method for determining the viscosity of plastic melts by using a falling ball viscometer. This method calculates the viscosity value of the sphere by observing the speed at which it falls in a heated plastic sample. The standard describes in detail the equipment requirements, specimen prepative, test conditions and data processing methods to ensure the accuracy and repeatability of the test process. The falling ball method can be used to evaluate the flow characteristics of different types of plastics in the molten state and is widely used in plastics processing, production quality control and research and development, especially for the measurement of high viscosity plastic materials. The test method is simple and effective, and has important reference value for the performance analysis of plastic products.