Abstract: A tray and conveyor for the trays are described, for moving liquid samples in an analyzer. The tray comprises a base having a magnetic member for responding to a magnetic field, a tray frame and member for freely rotatably mounting the frame on the base, the tray frame comprising a plurality of receptacles constructed to receive either sample tubes or aspirating tips useful to aspirate sample from a tube, the receptacles including a fixed bottom support. The conveyor comprises a support, conveying members under the support comprising a plurality of magnets and members for generating a moving magnetic field with the magnets, the conveying members being mounted in a continuous loop under the support and the support being permeable to a magnetic field, one of the above-noted trays being mounted above the support on the base.

Abstract: An electronically actuated shutter in which the location of the shutter blades are known to accurately control the aperture size and exposure. A gradient neutral density strip, a light source and a light detector are used to determine the position of the shutter blades.