| 摘要 |
A print head is attached to a stepper motor that moves the print head toward and away from the surface of a printing medium. During a gap setting operation, a controller controls the stepper motor to move the print head to a maximum distance away from the surface of the printing medium. A print wire actuator coil for the print wire used in the gap setting operation is then energized. The print head is then positioned over the printing medium and the controller controls the stepper motor to move the print head in towards the printing medium. When the energized print wire touches the printing medium, the print wire begins to be pushed back into the print head. As the wire is pushed back, an air gap between a yoke and a print wire armature is created. The opening of the air gap increases the amount of flux detected by a Hall sensor. When the output voltage of the Hall sensor reaches a predetermined level, the controller determines that the print wire has pressed the ribbon and printing medium against the platen. The controller then controls the stepper motor to establish the desired printing gap (e.g., by stepping back a predetermined number of steps).
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