Basically the title is the question. VJ-1324 will give me an ink low warning. I will keep printing until it stops saying the ink cartridge is empty. When I replace it the old cart seems to have plenty of ink still left in it. How does it measure the amount of ink? Is it by what it thinks it used, is there are sensor in the cartridge, the chip? How can I used all the ink? using GRS ink cartridges that previous owner was using.