Traceable amount of substance fraction measurements in gases through infrared spectroscopy at PTB

Abstract

Abstract. Gas analysis has become an important task in various fields of science and industry, especially through techniques based on laser spectroscopy. Common applications are, for example, the monitoring of the atmosphere to assess human impact on ecosystems and the climate, the monitoring of airborne molecular contamination to supervise sensitive high-tech processes like semiconductor manufacturing, or the analysis of combustion processes. High resolution laser spectroscopy lends itself particularly well for gas analysis, as it is fast, selective, and the results can be made traceable to the SI units. Traceability is of particular importance to maximize the reliability of measurement results, especially if such measurements are the input for complicated models like those used in climate research or if impacting political decisions. In this contribution we give an overview on our approach to achieve traceability of results from spectroscopic amount fraction measurements of H2O, CO2, and NH3 including the TILSAM method (traceable infrared laser-spectrometric amount fraction measurement). We discuss how this method applies to tunable diode-laser absorption spectroscopy (TDLAS), cavity ring-down spectroscopy (CRDS), and photoacoustic spectroscopy (PAS). This research is partly embedded in projects within the European Metrology Research Programme (EMRP).

Thermal Boundary Layer Effects on Line-of-Sight Tunable Diode Laser Absorption Spectroscopy (TDLAS) Gas Concentration Measurements

“…But the path-averaged information, e.g., temperature, is not always available in many applications such as cross-stack emission monitoring. Using the optical transfer standard dTDLAS method under conditions with temperature and/or concentration gradients, 25,26 the path-integrated spectra are measured together with temperature and pressure measurements (one or several sampling points along the LOS). The question is how to evaluate the measured spectra under such conditions.…”