A system to measure the flow rate of a liquid in a microfluidic circuit. The system includes a vessel that is partially filled with the liquid, a gaseous ceiling above the vessel and a pressure regulator to maintain the pressure of the gas in the gaseous ceiling at a predetermined value P1. A capillary pipe to extract the liquid from the vessel and to output the liquid at a pressure P2 lower than P1. A first inlet of the pressure sensor is connected to the gaseous ceiling, a second inlet of the pressure sensor is connected to the capillary pipe, and the outlet of the pressure sensor outputs a signal as a function of the pressure difference (P1−P2), which is a measurement representing the flow rate of pressurized P2 liquid supplied to the microfluidic circuit.