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.