Simple sensor system for measuring the dielectric properties of saline solutions

On-line measurements of dielectric properties can be used for quality determination of process streams. Measurements of the water cut are important in order to determine how much water and oil that are e.g. produced from an oil well or how much oil is discharged to the sea. This work describes the use of a single open-ended probe measurement system for determination of the dielectric properties of saline solutions, the salinity being an important parameter in the determination of the dielectric properties of the water. The frequency range of the measurements is from 500 MHz up to 40 GHz, the salinity varying from 0 to 3.5 wt% (sea water) at 20 degrees C. Models are developed under controlled laboratory conditions relating the static permittivity, relaxation time and conductivity to the salinity of the water. For model verification the same set of tests are performed with a well established precision laboratory system. The potential for on-line implementation of the open-ended probe has been verified by tests in a multiphase flow loop, and these results are also presented.