Automatic print cartridge alignment sensor system

A swath printing system for calibrating and correcting alignment differences between a plurality of nozzle arrays mounted on a carriage for printing on a pixel grid comprising:

• a first printhead with a first array of ink-firing nozzles;
• a second printhead with a second array of ink-firing nozzles;
• a carriage for mounting said first and second printheads in predetermined positions;
• a guide member mounting said carriage to allow said carriage to move back and forth along a carriage scan axis over print media;
• a motor for periodically advancing the print media in a path along a media axis;
• a position encoder operatively connected to said carriage to determine changes in position of said carriage along said carriage scan axis;
• and
• a controller coupled to said position encoder and said printheads for respectively activating said first array to print a first test line segment and said second array to print a second test line segment spaced apart from said first test line segment, and as a result of a perceived offset between said first and second test line segments, said controller maps data to arrive at the ink-firing nozzles when the nozzles are over an appropriate location of the pixel grid as said carriage traverses along said carriage scan axis.