A device for metering one or more powder(s) (A, B) to produce a flow (23) of powder(s) and of a carrier gas at a given volume flow rate, comprises: ⋅at least a first source (25) suitable for supplying a first flow (27) comprising a first powder (A) and a first carrier gas (G1) substantially at the given volume flow rate, ⋅a source (33) of a carrier gas suitable for supplying an adjustment carrier gas flow (35) substantially at the given volume flow rate, ⋅an outlet junction (49) for emitting said flow of powder(s) and of carrier gas, ⋅a first proportional valve (59), ⋅an adjustment proportional valve (75), and ⋅a control system (21) suitable for controlling at least the first proportional valve and the adjustment proportional valve so that the flow of powder(s) and of carrier gas has a volume flow rate substantially equal to the given volume flow rate.