A flow control valve assembly, and a method of determining and controlling fluid flow through the valve, that is relatively simple in design, is relatively inexpensive, is accurate, and has a relatively wide measurement range. The flow control valve is relatively compact and includes all of the flow measurement and control components in a single, relatively compact assembly. Such components may include a differential pressure sensor, pressure sensor, a temperature sensor, a position sensor, and a processor. The differential pressure sensor senses differential pressure across the variable area flow orifice. The pressure sensor senses fluid pressure within the valve and supplies a fluid pressure signal. The temperature sensor senses fluid temperature and supplies a fluid temperature signal. The position sensor senses the position of the variable area flow orifice and supplies a position signal. The processor receives the differential pressure signal, the fluid pressure signal, the fluid temperature signal, and the position signal and uses these signals to determine and control fluid flow parameter in the passageway.