Patent ID: 6375299
Filing Date: 2002-04-23
Classification: B41J

Abstract:
A piezoelectric ink jet printer incorporating ink ejector fault detection, said ink jet printer comprising:an ink jet print head comprising a plurality of ink ejectors, wherein each of said plurality of ink ejectors is piezoelectrically actuated so as to eject droplets of ink in accordance with print data received from a host computer system; a first drive circuit coupled to said host computer system and to said plurality of ink ejectors so as to control ink ejection therefrom during normal printing operations; a second drive circuit periodically coupled through a resistor to a selected one of said plurality of ink ejectors, wherein said second drive circuit is configured to apply a test signal through said resistor to said selected ink ejector during periods when said ink ejector is not being utilized for printing operations by said first drive circuit; a fault detection circuit having an input connected to at least one side of said resistor; wherein an electrical signal present at said at least one side of said resistor is detected by said fault detection circuit simultaneously with the application of the test signal, and wherein characteristics of said electrical signal are indicative of an operational status of said selected ink ejector, wherein said fault detection circuit comprises an analog to digital converter having as an input an analog signal derived from said electrical signal present at said at least one side of said resistor and having as an output a digital representation of said analog signal, and digital signal processor coupled to said output of said analog to digital converter for analyzing said digital representation of said analog signal and detecting faulty ink ejectors therefrom.