A biopsy apparatus includes a driver assembly to be grasped by a user and a disposable biopsy probe assembly for releasable attachment to the driver assembly. A carrier substrate includes a mounting region and an opening, which is formed in the mounting region of the carrier substrate. Despite that the bag is flexible, the powder container does not fall down when mounted to an image forming apparatus. When the capacitive component is selected and the first fuel injector is deselected, the diagnostic means is operable to sense a current through the first fuel injector. In variations, a difference between the first and second times signals a fault condition. Since the width of the upper core layer is larger than the track width, magnetic saturation can be effectively reduced.