A device making it possible to carry out wettability measurements under a controlled atmosphere, comprising an apparatus (5) for measuring the wettability of at least one surface portion of a sample by a liquid metallic solder, at least partially included in an enclosure (6) which includes a gas injector which comprises at least one set of ducts (10) mounted in series and/or in parallel, at least one portion of which includes gas injection orifices, and is fed by at least one gas supply pipe connected to the set at a primary connection node, the dimensioning of the set respecting the following relationship:.SIGMA..omega..sub.i /.SIGMA..phi..sub.i .gtoreq.1 preferably.gtoreq.1.5;where .SIGMA..omega..sub.i represents the sum of the internal cross sections of the gas supply pipes which feed the set and .SIGMA..phi..sub.i represents the sum of the cross sections of the gas injection orifices of the set of ducts.