Abstract: A method and circuitry for maintaining the precise temperature of atomic absorption spectroscopy graphite specimen tubes over wide temperature ranges independently of the tube emission factor. The infrared radiation of a heated tube is measured by a detector, the signal from which is amplified in a variable gain amplifier, then compared with an externally generated "temperature select" signal, and the error signal therefrom controls a circuit that in turn controls the heating power to the graphite tube. A second measurement of the heated tube is made by a detector sensitive only to short wavelength radiation, e.g., visible, which is substantially unaffected by emission factors, and the signal therefrom adjusts the gain of the variable gain amplifier to thereby correct the infrared generated signal for variation in tube emission factors.