Gas Measurement Using Static Fourier Transform Infrared Spectrometers

Abstract

Online monitoring of gases in industrial processes is an ambitious task due to adverse conditions such as mechanical vibrations and temperature fluctuations. Whereas conventional Fourier transform infrared (FTIR) spectrometers use rather complex optical and mechanical designs to ensure stable operation, static FTIR spectrometers do not require moving parts and thus offer inherent stability at comparatively low costs. Therefore, we present a novel, compact gas measurement system using a static single-mirror Fourier transform spectrometer (sSMFTS). The system works in the mid-infrared range from 650 cm−1 to 1250 cm−1 and can be operated with a customized White cell, yielding optical path lengths of up to 120 cm for highly sensitive quantification of gas concentrations. To validate the system, we measure different concentrations of 1,1,1,2-Tetrafluoroethane (R134a) and perform a PLS regression analysis of the acquired infrared spectra. Thereby, the measured absorption spectra show good agreement with reference data. Since the system additionally permits measurement rates of up to 200 Hz and high signal-to-noise ratios, an application in process analysis appears promising.

Infrared spectroscopic monitoring of solid-state processes

“…Additionally, with the use of a gas cell that allows an optical pathlength of up to 120 Hz, gases in the low ppm range can be accurately quantified. 196 The experimental protocol for quantitative IR measurements of gas sorption by solid materials is described in detail by Drenchev et al 16 The procedure and the power of the technique is demonstrated by the water-enhanced CO 2 adsorption on a metal-organic framework, UiO-66. For this purpose, a custommade system, consisting of a combination of high-and lowtemperature sample cells, was designed.…”

“…Additionally, with the use of a gas cell that allows an optical pathlength of up to 120 Hz, gases in the low ppm range can be accurately quantified. 196…”

Optical Design and Investigation of a Dual-Interference Channels and Bispectrum Static Fourier-Transform Imaging Spectrometer Based on Stepped Micro-Mirror

“…In 2018, Yan et al proposed a highresolution channel imaging spectral polarimeter using a liquid crystal variable retarder (LCVR) [13,14], the simulation experiment results showed that in the working range of 0.48-0.96 μm, the theoretical resolution of the spectrum could reach 40 cm −1 . In 2019, Michael et al proposed a mid-wave infrared hyperspectral imager based on a single-mirror interferometer structure [15][16][17][18], the hyperspectral data cube was obtained by the windowing method, and a spectral resolution of 12 cm −1 was achieved in 3.8-13 μm.…”

Adaptive Bad Pixel Correction Method for Interference-Modulated Images Based on Weighted Least Squares Support Vector Machines (WLS-SVM)

“…Temporally and spatially modulated Fourier transform imaging spectrometers (TSMFTIS) are a type of hyperspectral imaging sensors developed for airborne/spaceborne hyperspectral imaging. 1–6 A focal plane array (FPA) is usually used as the two-dimensional (2D) detecting sensor in TSMFTISs. However, because of the defects of the materials, the temperature unevenness of the production unit, the etching chemical material impure, manufacturing process, or other factors, certain pixels in the detector behave abnormally and are therefore called bad pixels, defect pixels, or blind pixels.…”