Differential Current Sensing System for Diagnostic Purposes
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Current sensing for self-diagnostic purposes is known. For example, in trouble shooting printer systems with the aid of a microprocessor, current sensing is used to differentiate between a shorted driver circuit condition and an open circuit condition between the driver circuit and the driven circuit. The driver circuits drive the hammer circuits, stepper motor circuits and relay circuits of the printer system. In case of a driver failure, all stepper motor drivers, which are normally on, would be degated and, of course, all hammer drivers would be turned off in response to the microprocessor. An error code is displayed in the microprocessor's status indicator display, which indicates either a driver turn-on failure condition, a driver turn-off failure condition, or the aforementioned open circuit condition.