The expressions of the second harmonic（2f） signal are derived on the basis of absorption spectral and lock-in theories.A parametric study indicates that the phase shift between the intensity and wavelength modulatio...The expressions of the second harmonic（2f） signal are derived on the basis of absorption spectral and lock-in theories.A parametric study indicates that the phase shift between the intensity and wavelength modulation makes a great contribution to the 2f signal.A self-calibration wavelength modulation spectroscopy（WMS） method based on tunable diode laser absorption spectroscopy（TOLAS） is applied,combining the advantages of ambient pressure,temperature suppression,and phase-shift influences elimination.Species concentration is retrieved simultaneously from selected 2f signal pairs of measured and reference WMS-2f spectra.The absorption line of acetylene（C2H2） at 1530.36 nm near-infrared is selected to detect C2H2 concentrations in the range of 0-400 ppmv.System sensitivity,detection precision and limit are markedly improved,demonstrating that the self-calibration method has better detecting performance than the conventional WMS.展开更多
A flow measurement system consisting of an optical fiber Fabry–Perot（F-P） sensor and an elbow tube is proposed and demonstrated to realize flow measurements and eliminate thermal disturbance.Two F-P sensors are sym...A flow measurement system consisting of an optical fiber Fabry–Perot（F-P） sensor and an elbow tube is proposed and demonstrated to realize flow measurements and eliminate thermal disturbance.Two F-P sensors are symmetrically mounted on the inner-wall surface of the elbow of 90° in order to eliminate the effect of thermal disturbance to the flow measurement accuracy.Experimental results show that the absolute phase difference is the square root of the fluid flow.It is consistent with the theoretical analysis,which proves that the flow measurement method can measure flow and eliminate the influence of thermal disturbance simultaneously.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61172047,61502538,and 61501525)
文摘The expressions of the second harmonic（2f） signal are derived on the basis of absorption spectral and lock-in theories.A parametric study indicates that the phase shift between the intensity and wavelength modulation makes a great contribution to the 2f signal.A self-calibration wavelength modulation spectroscopy（WMS） method based on tunable diode laser absorption spectroscopy（TOLAS） is applied,combining the advantages of ambient pressure,temperature suppression,and phase-shift influences elimination.Species concentration is retrieved simultaneously from selected 2f signal pairs of measured and reference WMS-2f spectra.The absorption line of acetylene（C2H2） at 1530.36 nm near-infrared is selected to detect C2H2 concentrations in the range of 0-400 ppmv.System sensitivity,detection precision and limit are markedly improved,demonstrating that the self-calibration method has better detecting performance than the conventional WMS.
基金supported by the National Instrumentation Program of China(No.2013YQ030915)the National Natural Science Foundation of China(Nos.61675152,61227011,61378043,61475114,61505139,and 61505138)+2 种基金the open project of Key Laboratory of Micro Opto-electro Mechanical System Technology,Tianjin University,Ministry of Education(No.MOMST2016-3)the Shenzhen Science and Technology Research Project(No.JCYJ20120831153904083)the SEM Soft Science Research and Development Project of Ministry of Housing and Urban-Rural Development of China(No.2016-K4-087)
文摘A flow measurement system consisting of an optical fiber Fabry–Perot（F-P） sensor and an elbow tube is proposed and demonstrated to realize flow measurements and eliminate thermal disturbance.Two F-P sensors are symmetrically mounted on the inner-wall surface of the elbow of 90° in order to eliminate the effect of thermal disturbance to the flow measurement accuracy.Experimental results show that the absolute phase difference is the square root of the fluid flow.It is consistent with the theoretical analysis,which proves that the flow measurement method can measure flow and eliminate the influence of thermal disturbance simultaneously.
