A capacitive sensor based measuring system for water content in crude oil is presented. The non intrusive capacitive sensor is made of two semi-cylindrical electrodes which are mounted on outside of the glass tube. The tube is filled with sample under test. The capacitive variation is measured by taking advantage of big dielectric permittivity difference of oil and water. The semi-cylindrical capacitive sensor has ability to detect small capacitance variation (pF) and these variations can be converted into voltage by proposed differential interface circuit. The interface circuit is based on differential sensing technique. Such technique allows the removal of unwanted signals (e.g. temperature, background noise and systematic offset) because they affect both sensors in a similar manner. It however will not auto-compensate for the degradation in sensitivity. Hence, increased accuracy and linearity is achieved by differential sensing technique. Both simulation and actual hardware implementation confirmed the proposed system design. The system is experimentally tested for 0-30 water content in oil and achieved resolution of 0.39. © 2014 Praise Worthy Prize S.r.l. - All rights reserved.