Abstract: A sensor for determining the overall content of a pre-determined chemical element in a liquid body uses X-ray fluorescence technology and includes an X-ray source, an X-ray detector, and a cell intended to contain a sample of lubricant to be analyzed, and is provided with a wall forming a window for passage of X-rays, the wall of the sensor cell being produced from polyethylene terephthalate, the cell also including a casing defining an internal volume for receiving the sample. A procedure for calibrating the sensor, and an automated method for online monitoring are also described and claimed.

Abstract: A method for determining a basicity index of a liquid body comprising: (a) detecting an intensity of an infrared signal passing through a sample of the liquid body; (b) calculating a transmittance value of infrared waves through the sample for p wave numbers, wherein p in a natural integer greater than or equal to two; and (c) determining the basicity index of the liquid body, BN, wherein of BN=Tr·M(p×1)+R, Tr is a set of transmittance values calculated in step b, M(p×1) is a set of data of a model, the set of data containing coefficients determined from measured basicity index values and measured transmittance values of reference liquid bodies, and R is a residue of the model, determined from the measured basicity index values and the measured transmittance values of the reference liquid bodies.