Abstract: A method of calibrating a level sensor is provided. The level sensor includes a tube, a lower part of which communicates with a liquid volume, an upper part not being filled with the liquid; and a device for measuring a level of the free surface of the liquid along the tube. The method includes placing the upper part of the inner space at a predetermined pressure; computing a theoretical level of the surface of the liquid; acquiring the measured level measured by the measuring device; comparing the theoretical level and the measured level; and repeating the steps for computing a theoretical level, acquiring a measured level and comparing the theoretical and measured levels after placing the upper part of the inner space at least at a second predetermined pressure.