Pyrometric temperature measurements in flameless atomic absorption spectroscopy
First Claim
1. Circuitry for automatically adjusting the calibration of a first pyrometric radiation detector for extended temperature range measurements of a heated atomic absorption spectroscope graphite tube independently of the radiation emission factor of said tube, said first radiation detector being positioned to receive radiation from said tube and generating an output signal indicative of the temperature thereof, said circuit including:
- a variable gain amplifier coupled to said radiation detector and responsive to the signal generated therefrom;
a second radiation detector positioned to sense the radiation emitted by said graphite tube, said second detector being accurate within a limited wavelength range and generating a second output signal that is independent of the emission factor of said graphite tube; and
circuitry means responsive to said second output signal for adjusting the gain of said variable gain amplifier whereby the output signal of said amplifier represents the temperature sensed by said first radiation detector corrected for emission factor;
the improvement comprising;
said second radiation detector being sensitive to a limited radiation wavelength range, the center of which is a shortwave with respect to a radiation emitted by said graphite tube, said second detector including said first radiation detector and a short wavelength transmitting filter interposable in the radiation beam from said graphite tube.
1 Assignment
0 Petitions
Accused Products
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.
5 Citations
5 Claims
-
1. Circuitry for automatically adjusting the calibration of a first pyrometric radiation detector for extended temperature range measurements of a heated atomic absorption spectroscope graphite tube independently of the radiation emission factor of said tube, said first radiation detector being positioned to receive radiation from said tube and generating an output signal indicative of the temperature thereof, said circuit including:
-
a variable gain amplifier coupled to said radiation detector and responsive to the signal generated therefrom; a second radiation detector positioned to sense the radiation emitted by said graphite tube, said second detector being accurate within a limited wavelength range and generating a second output signal that is independent of the emission factor of said graphite tube; and circuitry means responsive to said second output signal for adjusting the gain of said variable gain amplifier whereby the output signal of said amplifier represents the temperature sensed by said first radiation detector corrected for emission factor; the improvement comprising; said second radiation detector being sensitive to a limited radiation wavelength range, the center of which is a shortwave with respect to a radiation emitted by said graphite tube, said second detector including said first radiation detector and a short wavelength transmitting filter interposable in the radiation beam from said graphite tube. - View Dependent Claims (2, 3, 4, 5)
-
Specification