Oil-Water Interface Level Sensor Based on an Electrode Array

A novel liquid interface level sensor is presented that is able to determine the position of the interface between a conductive and an insulating liquid. The sensor consists of an array of equally spaced electrodes, two of which are used to inject a current into the conductive liquid and the remaining electrodes are used to measure the drop in voltage across the conductive medium. An inverse problem algorithm of the Levenberg-Marquardt type is used to adjust a theoretical model of the system to the experimental data. This procedure allows us to determine the position of the interface between two liquid layers with a resolution and accuracy better than the electrode spacing without using any previous calibration procedure. Measurements performed with a prototype electrode array with 5 cm interelectrode spacing, achieved a 1 cm accuracy and 0.3 cm resolution in determining the oil-water interface position in a cylindrical tank