Intelligent spectrometers and calibration schemes for single-beam instrumentation

Flexible, inexpensive fiber optic systems for real-time analysis were constructed and optimized. Spectrometer components were interfaced with different acquisition systems and sample cells to provide uniquely suitable configurations. Direct observation of chemical systems via fiber optics or indirect monitoring using probes was successfully performed after proper modeling and instrumental design were conducted. Additionally, the implementation of a microcontroller for spectrometer operation decreased the cost of the system and increased its portability and functionality.; A microcontrolled spectrometer was used to collect spectra for several different fiber optic systems. The first application was the quantitative monitoring of NO{dollar}sb2{dollar} gas as it exited a tall glass chimney above a reaction vessel. This application included a unique method of producing NO{dollar}sb2{dollar} gas standards and an absorbance calibration model. The second application was a Nd-doped glass, fiber optic temperature probe. The probe was designed to operate in a supercritical bomb and utilized a single-beam calibration scheme. The third application was a spectroscopic pH measurement based on visible indicators inside a supercritical bomb. An infrared remote LED display and a hard-wired LCD display were developed to complement these microcontroller-based applications.; Two unique calibration schemes were developed and tested. The first was for an unreferenced ZnSe fiber optic temperature probe. The calibration scheme involved monitoring the shift in the spectral cutoff of the ZnSe at different temperatures. The second involved Genetic Regression (GR) which was used to build a calibration model for a single-beam spectrometer of traditional benchtop design. This algorithm was tested using: single-beam data for aqueous NaNO{dollar}sb3{dollar} and CoCl{dollar}sb2{dollar} solutions. Tests on the short and long-term accuracy showed that the genetic calibrations were superior to traditional absorbance calibrations. Both of these calibration schemes were designed to work using the sample-beam spectra only.