General:
Graphically represented mutual dependency between two operating variables, often with a constant third being used as the parameter.
Example: In Figure D79, the flow rate Q is applied to a control edge in relation to the pressure difference p, with the opening cross section (as a % of the maximum opening) being used as the parameter.
A linear characteristic curve applies if the relationship between two variables is represented as a straight line. In general, however, relationships tend not to be linear, which means it is necessary to linearise them for many purposes.
Characteristic curve for continuously adjustable valves:
The (static) characteristic curve describes the relationship between the stationary value for the input signal and output signal variable. It is non-linear in general and, as such, is represented graphically in most cases. The linearised functional relationships only apply therefore to small parts of the transfer function.
For continuously adjustable valves with more than one input signal (flow rate, pressure), performance maps will be specified. The parameters kept constant in this regard need to be applied to the curve with their respective values (EDIN 24 311).