Real-time monitoring of working fluids such as fuels, lubricants, hydraulic fluids, and coolants provides a valuable window into the 'blood chemistry' of machines for current health and useful-life-remaining analyses. Therefore it increases dependability and reduces required maintenance manpower, allowing more streamlined support structures. Such applications demand state-of-the-art sensors which are compact, easy to install, network-ready and dependable in potentially adverse environments. At Physical Sciences Inc., Angularly resolved, polarmetric and quasi-elastic light scattering monitors have been developed for in-line, real time particulate contamination determination. Similarly, miniaturized FTIR, Non-Dispersive IR, Quantum Cascade Laser and Tunable Diode Laser absorption devices have been used for the detection of dissolved contaminants and bulk fluid parameters including dissolved water and solvent contamination. One of the used optical sources is a heated tungsten element or glowbar, which provides a very broad band radiation spectrum according roughly to the blackbody emission for the element temperature. Because the emission bandwidth is broad, the NDIR sensor can typically make absorption measurements from about 1 to 20 microns wavelength. Following the light source a filter selects the wavelength band of interest: These filters are generally inexpensive and may be engineered to correspond to any center wavelength in the range of the thermal source. Following the sample cell, a photo-detector, typically a thermopile, quantitatively determines the light power transmitted through the sample at the selected band. Despite their relatively slow response time, thermopile detectors are used because of their ability to inexpensively and accurately detect light energy throughout the blackbody spectrum of the thermal source. The electrical signals from the detector are typically digitized and compared to calibration curves for known contaminants stored in the memory of the NDIR unit. Besides a review of these technologies a case study of manpower reduction aboard a U.S. Navy aircraft carrier by automated laser fluid monitoring is presented.
Photonic sensors for condition based monitoring
2003
10 Seiten, 9 Bilder, 2 Tabellen
Aufsatz (Konferenz)
Englisch
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