As a generic ‘tool’ electrical impedance tomography (EIT) is useful in improvingthe modelling and design of many complex processes and for process control(Williams R A and Beck M S 1995 Process Tomography: Principles, Techniquesand Applications (Woburn, MA: Butterworth Heinemann) pp 11–25, Neuffer D,Alvarez A, Owens D H, Ostrowski K L, Luke S P and Williams R A 1999 Proc.1st World Congr. on Industrial Process Tomography (Buxton, UK) pp 71–7).However, existing developments of the EIT technique are only applicable toaqueous-based fluids that possess continuous admittance property (Xie C G,Reinecke N, Beck M S, Mewes D and Williams R A 1994 Process Tomography—AStrategy for Industrial Exploitation ed M S Beck pp 25–32). For example, itwould not be suitable for a stratified flow or an intermittent flow in ahorizontal channel or large bubble formation and foams since some of theelectrodes may lose contact with the conductive fluid. The paper reports apreliminary study of a novel sensor and apparatus, which seeks to address somesignificant shortcomings in EIT application through use of a new sensingstrategy and apparatus for measuring complex multiphase flows, such asoil/gas/water flow or bubble formation and foams. The major feature of thesensing system is to employ a single conductive ring as a tomographicsensor instead of a number of electrodes as in conventional EIT. Thestrategy facilitates a more homogeneous sensitivity distribution throughoutthe sensing domain of the conductive ring, which is less affected by thecontact area or geometry of electrodes than in previous EIT systems. Thesensor can be conveniently constructed as a flange-based flow sensor,if required, without the need to drill holes in the pipe wall. Therefore,it provides a realistic way to measure the dynamic changes of flowingfluids. The novel methodology is believed to offer a significant advance inenabling a more flexible and robust EIT system to be devised for on-linemeasurement and control of flow in oil, pharmaceuticals and food industries.