Determining defective resistors in inkjet printers

摘要

A method and apparatus for determining defective heating resistors R_i in each of a plurality of inkjets in an inkjet printer, wherein each heating resistor R_i is connected in parallel with a common capacitor, the method for each heating resistor R_i includes providing a variable power supply effective in a first condition to produce a first operating DC voltage and, in a second condition, to produce a second known test DC voltage V_t, and inserting a known reference resistor R_r in series with the heating resistor R_i and capacitor and also open circuiting the capacitor in response to sensing that the power supply has changed from the first condition to the second condition. The method and apparatus further include digitizing the voltage V_i at the electrical junction between the heating resistor R_i and the reference resistor R_r, and using the digitized voltage to determine if the heating resistor R_i is defective.