How does your computer determine the remaining ink in the cartridge?

Inkjet printer ink is notoriously expensive. Depending on your printer’s brand and model, you could easily spend $100 or more on a new set of cartridges – all for a printer that may have cost only $89. So, when you want to stretch that pricey ink, you might wonder how the printer knows when each cartridge is running low.

Before getting into the specifics, it’s important to know that manufacturers intentionally program printers to stop using cartridges that are running low on ink. If a cartridge were to run completely dry, the plastic might overheat and damage or destroy the printer’s printhead. In short, you'd end up with a broken printer, not just an empty cartridge.

Given the high cost of ink, it's in your best interest to extract every last drop from each cartridge. Ink can cost anywhere from $13 to $75 per ounce. That’s nearly $10,000 per gallon [source: Consumer Reports].

Ink is outrageously priced partly because printer manufacturers sell their advanced printers at a very low initial cost, knowing that their real profits will come from ink sales over time.

This brings us to an important point: If ink is such a lucrative source of income for printer companies, they'd have a clear incentive to exaggerate low-ink warnings. After all, if you replace cartridges prematurely when there's still usable ink, ink sellers will see a significant boost in their profits.

However, these companies aren’t necessarily trying to rip you off. On the next page, you’ll discover more about low-ink warnings and how you can track whether you’re getting your money’s worth.

Low-Ink Tech

So how does your printer know when the ink in a cartridge is running low? Different manufacturers use various technologies to monitor this process.

Epson’s cartridges have an integrated circuit chip that not only verifies if the correct cartridge is in place but also keeps track of how much ink each cartridge has used. When the ink reaches a low level, the chip alerts your computer, and you receive a notification on your screen.

Canon takes a different route. Its printers are equipped with an optical sensor that shines light through a prism at the bottom of the ink well. As ink levels drop to a set point, the light reflects back to a low-ink sensor, triggering a message to tell you it’s time to replace the cartridge.

Some printer manufacturers design their printheads directly on the cartridge, which eliminates the risk of damaging the printer once the ink runs low. These printers often use a chip similar to Epson’s. However, some models refuse to print even with ink left, forcing you to discard usable ink.

The big question is how accurate are these systems? Journalists and industry experts have mixed views on ink yield, but the general consensus is that manufacturers tend to overestimate low-ink warnings. In other words, they’d rather you replace a cartridge that still has ink than let you continue printing for weeks or months and delay your next purchase. One study found that nearly 60 percent of ink is wasted and thrown away [source: Haworth].

If you're worried about ink prices, it's wise to research before purchasing a printer. Typically, the cheaper the printer, the higher the ink costs. Opting for a slightly more expensive printer might reduce your ink expenses over time [source: Wood].

Another consideration is leaving your printer powered on. Every time you turn an inkjet off and on, it performs a maintenance cycle that uses a significant amount of ink from each cartridge [source: Consumer Reports].

Print only when necessary and keep the printer on to maximize the life of each cartridge. This way, you’ll hopefully save some money in the process too.