A three dimensional (3D) printing system includes an ink cartridge providing ink to a printhead and a controller. The ink cartridge also includes a flag material and a sensor component. The ink has a low dielectric constant and defines an upper surface having a vertical position defining an ink level. The flag material has a high dielectric constant and is disposed upon the upper surface of the ink. The sensor component includes a vertical arrangement of electrodes proximate to the ink. The controller is coupled to the sensor electrodes and is configured to: (1) scan sensor electrodes to determine a capacitance between adjacent pairs of electrodes, (2) identify at least one pair of electrodes having a peak capacitance value relative to capacitance values of remaining pairs of electrodes, and (3) estimate the ink level based upon the identification.