The device comprises a source of gas under pressure, a measurement branch connected to the source of gas under pressure and including a feed nozzle and a measurement member, a measurement pressure sensor connected to the measurement branch between the feed nozzle and the measurement member, and an absolute pressure sensor connected to the source of gas under pressure and having an input connected to a reference electricity source and an output connected to an input of a differential amplifier having another input connected to the reference electricity source and an output connected to the power supply terminal of the measurement pressure sensor.