The diameter is updated each revolution of the roll. This method requires a means of determining when a revolution is complete. Usually this is done by calculation of the last diameter times π and a length of wound web. Occasionally the web length is determined by integrating the line speed.
Problems with this method of diameter calculation are that it is not self starting – the core diameter must be entered. In addition, a known accurate product gauge must be entered. If the gauge changes with wound in tension, the diameter calculation will not be accurate. If a web break and subsequent splice is performed on a roll, any product slabbed off is not accounted for.
The tolerance of variables associated with this method of diameter calculation suggest other methods be implemented.