Patent ID: 7178783
Filing Date: 2007-02-20
Classification: G05D

Abstract:
1. A method for automatic valve characterization of digital valve positioners, comprising the steps of: determining a minimum travel position of a valve through which fluid is to flow in a controllable process; inputting a control signal at an initial value to a digital valve positioner that controls a travel position of the valve in response to a value of the control signal, the initial value of the control signal corresponding to the minimum travel position of the valve and a respective amount of flow to define a minimum operating point; increasing the value of the control signal input to the digital valve positioner from the initial value to move from the minimum operating point through a series of operating points having respective control signal values, travel positions and amounts of flow, the series ending in a highest operating point defined by a highest travel position used thus far in the controllable process and the respective control signal value and respective amount of flow; for each operating point, storing at least the respective travel position and amount of flow; automatically generating a graphical straight line fitted between a point represented by the minimum travel position and its respective amount of flow and a point represented by the highest travel position and its respective amount of flow; and using the straight line as a modified installed flow characteristic for the valve to control the controllable process.