Device and method for determining sufficiency of ink supply for ink jet recording apparatus

摘要

An ink jet recording apparatus comprises a detachably mountable ink jet cartridge including an ink jet recording head for ejecting ink into a recording medium and an ink supply source containing ink for supply to the recording apparatus, which ink supply source has electrodes for passing an electric current through the ink in said ink supply source. A resistance-determining circuit determines a reference resistance between the electrodes by applying an electric current thereto when the ink jet cartridge is mounted to the apparatus and determines a test resistance between the electrodes by applying the same electric current thereto after a predetermined amount of recording. The reference resistance is used to calculate a threshold resistance, which is stored for comparison to the test resistance to judge whether or not the amount of ink in the ink supply source has dropped to a level unsuitable for recording.