The results of the calibration operations shall be recorded in a calibration certificate which is accompanied by digrams and tables showing, in particular, the volume of liquid, expressed in litres or cubic decimetres or cubic metres, which
is in the tank when the level of the free surface of the liquid is at a given height, expressed in centimetres or decimetres, on the vertical face of the measure of length. ... The vertical face of the measure of length at which the
heights of the liquid are determined shall pass, as a general rule, approximately through the centre of gravity of the horizontal sections of the tank, in every part where a free surface of the liquid may occur when measurements are made
under normal conditions of use.
