A method for operating a flow-control valve within a fluid system, comprising: providing a command signal to the flow-control valve to change its position sufficiently to achieve a flow rate that equals the flow rate setpoint; the method characterized by: computing a plurality of original iso-curves in non-transitory computer media associated with an electronic controller, each of the plurality of original iso-curves containing information correlating a valve position with a flow through the flow-control valve; receiving in the electronic controller an external control signal (202, 205) provided to the electronic controller and correlating the external control signal to a desired flow rate, the correlation being performed using a selected one of the plurality of original iso-curves, the external control signal being indicative of a parameter setpoint other than a desired flow rate setpoint, and designating the selected one of the plurality of iso-curves as an original iso-curve; automatically establishing a flow rate set point that corresponds to the desired flow rate in the original iso-curve, the flow rate set point being equal to the parameter setpoint; adjusting the command signal, in real time, as necessary, based on the original iso-curve, such that the flow through the control valve remains unchanged; selecting a different iso-curve to replace the original iso-curve with an updated iso-curve from the plurality of iso-curves when the flow through the flow-control valve falls outside of a predetermined threshold relative to the desired flow rate setpoint; wherein selection of the updated iso-curve is performed by the electronic controller based on a valve flow coefficient and other constants, which are determined in the electronic controller based at least in part on a valve flow signal indicative of the actual flow through the flow-control valve that is received by the electronic controller. computing a plurality of original iso-curves in non-transitory computer media associated with an electronic controller, each of the plurality of original iso-curves containing information correlating a valve position with a flow through the flow-control valve; receiving in the electronic controller an external control signal (202, 205) provided to the electronic controller and correlating the external control signal to a desired flow rate, the correlation being performed using a selected one of the plurality of original iso-curves, the external control signal being indicative of a parameter setpoint other than a desired flow rate setpoint, and designating the selected one of the plurality of iso-curves as an original iso-curve; automatically establishing a flow rate set point that corresponds to the desired flow rate in the original iso-curve, the flow rate set point being equal to the parameter setpoint; adjusting the command signal, in real time, as necessary, based on the original iso-curve, such that the flow through the control valve remains unchanged; selecting a different iso-curve to replace the original iso-curve with an updated iso-curve from the plurality of iso-curves when the flow through the flow-control valve falls outside of a predetermined threshold relative to the desired flow rate setpoint; wherein selection of the updated iso-curve is performed by the electronic controller based on a valve flow coefficient and other constants, which are determined in the electronic controller based at least in part on a valve flow signal indicative of the actual flow through the flow-control valve that is received by the electronic controller.