Optimal quality of the product that leaves a water/oil/gas separator is determined by optimal separator design and control. Current control strategies for separators are extremely simple due to the lack of a reliable interface level measurement system. In this project a capacitance-based tomography system for interface imaging inside a separator has been developed and tested in the separator laboratory at Christian Michelsen Research (CMR). The tomography system consists of a capacitance sensor system, a data acquisition system and a model-based reconstruction algorithm implemented on a personal computer. The system can potentially measure the water, oil/water emulsion, oil and foam heights inside a separator on a process plant. In this project the tomograph has been tested, in a separator laboratory at CMR, for on-line imaging of water, oil and air interface levels (during waterloillair tests) and for oil, foam and air interface imaging (during oillair tests). The obtained accuracy is within 1 .O cm for all phases. The tomograph also detected the presence of foam, but due to problems with electrostatic charge generation, poor Stability in the measurements results. In a steel separator, however, it is expected that t h e electrostatic charge problem will probably not exist,