1. A process for determining the levels and interface in a vessel of two or more immiscible or partially-miscible liquids comprising: a) transmitting energy selected from the group consisting of gamma rays and x-rays through the vessel by sequentially activating at least three stationary energy sources positioned adjacent to and in the vertical plane of the vessel; b) sensing a set of intensities of the energy exiting the vessel corresponding to each energy source using an array of stationary sensors where each set comprises the intensity sensed by each sensor in the array of sensors, said sensors of the array positioned in the vertical plane of the vessel and in alignment with the energy penetrating the vessel, said array containing a number of sensors that is at least one greater than the number of energy sources; and c) recording the sets of intensities sensed by the array and applying an algorithm selected from the group consisting of partial least squares with latent variables, multiple linear regression, principal component regression, and neural networks to the aggregate of recordings to determine the levels and interface of the liquids and any emulsion of the liquids.