Abstract: An external calibration system for a photo multiplier tube is described. The calibration system uses a light emitting diode and a photo cell wherein the diode is domed shaped. The light sensitive face of the photo multiplier tube is contained in the plane disposed at an acute angle to the longitudinal axis of the light emitting diode, and the photo cell is mounted substantially perpendicular to the longitudinal axis. A source of electrical energy then illuminates the light emitting diode over a range from, for example, 0 to 5 volts to generate light of known intensity and the light being generated is simultaneously measured by the photo cell and the light sensitive face of the photo multiplier tube. A feedback circuit is provided and associated circuitry so that a number of readings can be taken over a wide variety of light intensities to generate a calibration for the photo multiplier tube.

Abstract: A calibration system for a measuring device utilizing a photo multiplier tube is provided. The calibration system is intended to provide a stable light source variable over a wide range of intensities which can be used to calibrate the PMT reading using a closed loop feedback circuit. The LED and a photo cell are disposed in a reference block chamber whereby the photo cell is in close proximity disposed perpendicular to the axis of the LED. The LED being dome shaped will direct light energy on to the photo cell, and also peripherally. The PMT is disposed adjacent the LED and at an angle to its longitudinal axis whereby light generated by the PMT simultaneously strikes both the photo cell and the PMT without reflection.

Abstract: An improved luminometer is provided which uses a top loading plate carrier which receives a microtitration plate and uses a mask having an aperture corresponding to each test cell in the plate carrier. When the mask rotates downwardly to cover the microtitration plate, the plate carrier automatically orients the microtitration plate in the X, Y and Z directions. Reagents are added to the individual test cells through the mask aperture. Each reagent injector is extendable and retractable so that liquids can be added below the mask aperture during purging or washing and then the injector retracted. A pump is provided for each injector which is driven by a stepper motor and a rack and pinion connection to a syringe.