Abstract: A printing system for a shuttle-type printer includes a platen and a carriage configured to move bidirectionally across the platen. An optically responsive demarcation is provided on the platen outside of the media feed path. A printhead and an optical sensor are disposed on the carriage. During operation, the carriage is operable to position the optical sensor over the platen demarcation, whereby the optical sensor generates a position signal when it detects the platen demarcation. A control subsystem is operably coupled to the optical sensor to determine absolute position of the carriage relative to the platen in response to optical identification of the platen demarcation by the optical sensor. Several methods for operating such a printing system are also described.

Abstract: A method and apparatus for detecting ink flow through the printhead of an inkjet pen includes sensing the temperature of the printhead substrate as the inkjet pen prints a test pattern into the printer spittoon. The method includes printing a test pattern and storing data representing the temperature of the printhead. The method includes summing the change in temperature of the printhead between an initial point and points at intervals during the printing of a test pattern to provide a thermal history of the printhead. Ink flow is determined from the rate of temperature change during the printing of a test pattern, and from the change in thermal history of the printhead among test patterns.

Abstract: A method and apparatus for detecting the sufficiency of ink flow through the printhead of an inkjet pen comprises sensing the temperature of the printhead substrate as the inkjet pen prints a test pattern into the printer spittoon. The method compares a first change in temperature resulting from printing one portion of the pattern to a second change in temperature resulting from printing a second portion of the pattern. Based on this comparison, the sufficiency of the ink flow is determined. The comparison is done using a ratio of the second temperature change to the first temperature change. As the ink flow decreases, the second change in temperature rises faster than the first change in temperature and thus the ratio increases. By monitoring the ratio, comparing it to predetermined values and repeating the test pattern on a periodic basis, the method determines when the ink flow has dropped to a point that the pen should be replaced.