A method of determining a mass variation of a conductive film on a substrate with an area, an edge zone, and a center zone, is disclosed. The method includes providing a measured conductive film mass of a conductive film on a substrate. The method also includes positioning a sensor near a set of positions on the substrate; measuring using the sensor a set of electrical responses; and correlating the set of electrical responses to a set of conductive film thicknesses. The method further includes estimating a volume of the conductive film based at least in part on the set of conductive film thicknesses and the area; and estimating a derived conductive film mass based in part on the volume and a conductive film density, wherein the mass variation is a difference between the measured conductive film mass and the derived conductive film mass.