Abstract: A positioning system for a sample testing machine includes a base pan and a set of independent drive systems for sliding a sample tray across the base pan. Each of the drive systems includes a paddle that engages a side of the sample tray. The paddle is slideably mounted to a shaft with a collar that slides over the shaft. A motor and drive belt is provided to move the collar along the shaft, causing the paddle to engage the side of the sample tray and slide the sample tray across the base pan. Track sections are provided in the base pan to prevent the sample tray from rotating as the paddle slides the sample tray across the base pan.

Abstract: A diluting station and a pipetting station for a machine such as a biological sample testing machine. The diluting station has a rotating shot tube that fills with diluent without the need for priming when the shot tube is in a vertically inclined orientation, and which dispenses the diluent into a receptacle when the shot tube is rotated to a downward orientation. A thimble valve is placed in the shot tube to control the flow of diluent into the valve.The pipetting station includes a cylindrical housing storing a plurality of straws and a concentric rotating drum that sweeps a straw into a straw withdrawal slot. A tubular tapered transfer pin is inserted into the straw frictional into engagement with the straw. The tubular transfer pin rotates the straw out of the slot into a generally downward orientation towards a receptacle containing a fluid. The pin and straw are lowered so as to place the end of the straw into the fluid.

Abstract: A sample card transport station moves a test sample card from an incubation station for the card to a transmittance and fluorescence optical station in a sample testing machine. The sample card transport station has a drive belt and an associated stepper motor. The belt supports the card from one side of the card. A ledge having a card slot is disposed above the belt. The card is snugly received within the card slot, and supported from below by the drive belt and rollers for the belt. When the motor turns the belt, the belt grips the card and slides the card along the slot to the optical stations, without any slippage between the belt and the card. This construction provides for precise control over the movement of the card.

Abstract: A reagent for proteolytic enzyme assays has the general formula ##STR1## where RCO-- is an enzyme reactive acyl, such as an amino acid, peptide or substituted amino acid or peptide. The reagent may be hydrolysed by proteolytic enzymes and developed to form a distinctive color. The reagent may be formed by reacting RCOOH with N-hydroxysuccinimide to form the acyl N-hydroxysuccinimide ester. The ester may then be reacted to form the reagent.