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.
ABSTRACT
The condition of lubricating oil used in automotive and industrial gearboxes must be controlled in order to guarantee optimum performance and prevent damage to machinery parts. In normal practice, this is done by regular oil change intervals and routine laboratory analysis, both of which involve considerable operating costs. In this paper, we present a compact and robust optical sensor that can be installed in the lubrication circuit to provide quasi-continuous information about the condition of the oil. The measuring principle is based on non-dispersive infrared spectroscopy. The implemented sensor setup consists of an optical measurement cell, two thin-film infrared emitters, and two four-channel pyroelectric detectors equipped with optical bandpass filters. We present a method based on multivariate partial least squares regression to select appropriate optical bandpass filters for monitoring the oxidation, water content, and acid number of the oil. We perform a ray tracing analysis to analyze and correct the influence of the light path in the optical setup on the optical parameters of the bandpass filters. The measurement values acquired with the sensor for three different gearbox oil types show high correlation with laboratory reference data for the oxidation, water content, and acid number. The presented sensor can thus be a useful supplementary tool for the online condition monitoring of lubricants when integrated into a gearbox oil circuit.
ABSTRACT
Fourier transform spectroscopy has established itself as the standard method for spectral analysis of infrared light. Here we present a robust and compact novel static Fourier transform spectrometer design without any moving parts. The design is well suited for measurements in the infrared as it works with extended light sources independent of their size. The design is experimentally evaluated in the mid-infrared wavelength region between 7.2 µm and 16 µm. Due to its large etendue, its low internal light loss, and its static design it enables high speed spectral analysis in the mid-infrared.
ABSTRACT
This paper presents an approach of an innovative measurement principle for the quality control of viscous materials during a manufacturing process based on fluorescence imaging. The main contribution to the state of the art provided by this measurement system is that three equal fluorescence images of a static or moving viscous object are available in different optical paths. The independent images are obtained by two beam splitters which are connected in series. Based on these images, it is possible to evaluate each image separately. In our case, three optical bandpass filters with different center wavelengths of 405 nm, 420 nm, and 440 nm were used to filter the separate fluorescence images. The developed system is useable for the detection of impurities in the micrometer range. Further, incorrect mixing ratios of particular components and wrong single components in the viscous materials can be detected with the setup. Moreover, it is possible to realize static and dynamic measurements. In this case the maximum speed of the objects was 0.2 m/s for the dynamic measurements. Advantages of this measurement setup are the universality due to the use of optical standard components, the small dimension and the opportunity to integrate it easily into ongoing processes. In addition, the measurement system works on a non-contact basis. Thus, the expense for maintenance is at a very low level compared to currently available measurement setups for the investigated application. Furthermore, the setup provides for the first time a simultaneous analysis of more than one component and the detection of impurities concerning their nature and size in a manufacturing process.
