I have been told that the print head has a chip that keeps track of each
cartridge, so when you refill it the computer will still think that it is
empty. Is that correct? thanks
There is no chip on the cartridge. Instead, each cartridge has a unique
ID code. Your printer remembers the current and previous cartridge. When
it sees a new code, it assumes it's a full cartridge, and starts keeping
track of ink used, subtracting it from the full value over time. The
previous-previous cartridge is deleted, and the old current becomes the
new previous. If you swap between two cartridges, it will simply ping-pong
back and forth.
To reset the ink for a given cartridge, you either need to cycle through
3 cartridges, or use some routines involving taping over contacts to alter
the ID to emulate rotating through 3 cartridges.