Abstract: A method relating to deposition of a liquid sample mixture in the tubular furnace of a spectrophotometer. The method involves drawing a quantity of each ingredient of the sample mixture into a conduit in a predetermined sequence and also drawing a slug of air into the conduit immediately following the uptake of each ingredient. In the result, a segmented fluid stream is created in which a slug of air separates each two adjacent ingredient segments. The conduit is initially filled with a rinsing fluid and the segmented fluid stream displaces some of that rinsing fluid from the conduit. A slug of air separates the rinsing fluid from the segmented stream. The segmented stream is then discharged in a single operation into the furnace of the spectrophotometer so that mixing of the ingredients occurs at or adjacent the furnace surface.

Abstract: In a scanning spectrophotometer, in which a narrow wavelength band of radiation can be selected from a range of wavelengths for transmission alternately through a sample cell and a reference cell, continuous automatic baseline correction is provided. A pulse train signal is generated, wherein the number of pulses represents the ratio of a parameter (e.g., intensity) of the radiation transmitted, respectively, through the sample and reference cells. A ratio of unity represents the baseline, and deviations from the baseline are indicated by changes in the number of pulses in the pulse train. Digital information indicative of baseline deviations is stored in a memory device when the spectrophotometer is being calibrated, and is retrieved from the memory device during operation of the instrument for sample analysis. The retrieved information generates a correction signal, which provides a continuous baseline correction.

Abstract: Chemical analysis apparatus such as a spectrophotometer including an atomizer for receiving a sample to be analyzed and being heated by resistance heating. Control means being provided to vary the voltage across the atomizer, and consequently its temperature, and a feedback circuit is connected between the atomizer and the control means and includes components which are operable to generate an electrical analogue which at least approximates the heating response characteristics of the atomizer. The feedback circuit functions as a negative feedback loop so as to modify the power input to the atomizer by application of the aforementioned electrical analogue, and in that way substantially compensates for the heating response characteristics of the atomizer such that the temperature time profile of the atomizer follows a predictable path.

Abstract: Chemical analysis apparatus such as a spectrophotometer, having a carbon rod or other non-flame atomizer which is adapted to be heated by electrical resistance heating. The atomizer is included in a heater circuit, and a particular relationship exists between the electrical resistance of the atomizer and the electrical resistance of the remainder of that circuit. That relationship is such that variations in the atomizer resistance as may occur over a period of use, do not substantially affect power dissipation in the atomizer during heating. Ideally, the two resistance values are equal, but variations from the ideal are satisfactory in practice. A feed-back circuit is arranged to maintain a substantially constant voltage across the heater circuit, and that is achieved by comparing the applied voltage with a reference voltage and modifying the applied voltage as necessary to maintain a predetermined relationship between the two.

Abstract: A slit device for use in optical systems, and in particular for use in spectrophotometers. The device comprises an integral plate structure having two jaw assemblies, each of which includes two jaws arranged to define a slit between them, and flexible hinge means interconnecting the two jaws to permit relative movement such that the slit width can be varied. Each hinge means includes a part of the plate structure which has been turned on edge relative to the plate structure parts forming the associated jaws so as to have maximum flexibility in the general direction of relative movement of the jaws. Two bridging portions are also formed as integral parts of the plate structure, and each bridging portion connects one of the jaws of one jaw assembly with a jaw of the other assembly. Thus, movement of one jaw in one assembly is transmitted to a jaw of the other assembly through one of the bridging portions.