This work presents the development process for modeling an ECT (Electrical Capacitance Tomography) sensor using FEM software package COMSOL Multiphysics. The physical sensors are 3D dimensional but it has been common to model the slice or the cross–section in 2D. This project shows the modeling approach for 2D and 3D geometries, the linear Finite Element method (FEM) using COMSOL Multiphysics is developed in order to obtain the capacitance between electrodes when an electric field is applied and to obtain the permittivity distribution inside the closed pipe from the sensor. Generated phantoms and measured values are presented for empty and annular pattern. Simulation is verified using phantoms inside the 16 electrode sensor. The ECT model is representative by existing hardware, Portable ECT, PROTOM Research Group UTM.