So far I've seen that a pressure regulator regulates the pressure from upstream to required pressure downstream and that a flow regulator regulates the flowrate, obviously. But, theoretically, doesn't one regulate the pressure to induce a specific flowrate? what is the actual difference between these two devices (in theory or in practice)? I've also seen that flow regualtors are more predominant in liquid applications and pressure regulators are more common in gas applications. Compressibility of a gas, I would assume, makes it more difficult to regulate the flow of a gas compared to liquid. Any other ideas or differences that people may know of? Any help is appreciated as always, thanks.