- 标题
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Pressure measurement in combusting and non-combusting gases using laser-induced grating spectroscopy
摘要： The measurement of pressure using laser-induced thermal grating spectroscopy, LITGS, with improved accuracy and precision is reported. Pressure values are derived from the record of the time-profile of LITGS signals by fitting of modelled signals to experimental data. The procedure is described for accurate modelling of the LIGS signals involving a sequence of calculation steps with appropriate weighting and calibration to determine the best-fit value of pressure-dependent parameters for averaged and single-shot measurements. Results are reported showing application of this model-fitting method to measurements of pressure in static cells using LITGS generated from NO in mixtures containing N2 at pressures in the range 0.5–5.0 bar with accuracy of 1–3% and single-shot precision of 4–7%. Time-resolved measurements of pressure, using LITGS signals generated in toluene-seeded fuel vapour, during the compression and expansion strokes of a motored optically accessible engine are reported with pressure-dependent accuracy ranging from better than 10 to around 20% over the cycle and single-shot precision in the range 5–15% over the same range. Measurements in the engine under firing conditions were obtained over a limited range and slightly increased uncertainties associated with varying composition resulting from exhaust gas residuals. The method was found to be of limited utility for measurements in high temperature flames at around ambient pressures.
关键词： Combustion,Laser-induced thermal grating spectroscopy,Non-combusting gases,Pressure measurement,LITGS
更新于2025-11-25 10:30:42
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Cuff-less continuous measurement of blood pressure using wrist and fingertip photo-plethysmograms: Evaluation and feature analysis
摘要： Continuous monitoring of blood pressure improves prevention and control of cardiovascular diseases. Currently, cuff-based oscillometric sphygmomanometers are commonly used to monitor the systolic and diastolic blood pressure. However, this technique is discontinuous in nature and inconvenient for repeated measurements. Here we have proposed indirect measurement of blood pressure from photo-plethysmograms (PPG) simultaneously recorded from wrist and fingertip. The signals were recorded from 111 participants and different morphological features were obtained from PPG and its second derivative, acceleration plethysmograms (APG). Moreover, different measures of pulse transit time (PTT) and pulse wave velocity (PWV) were obtained from the recorded PPGs. Multi-layer Neural Networks were used to estimate the non-linear relationship between these features and systolic and diastolic blood pressures (SBP and DBP). Mean absolute errors of 6.77 and 4.82 mmHg were achieved in comparison with measurements from a validated commercial oscillometric sphygmomanometer. Feature analysis provided insight about the importance of features for estimating BP, and demonstrated that these features are not the same for SBP and DBP. Using the highest-ranked 15 and 13 features obtained from moving-backward algorithm the mean absolute errors were reduced to 5.31 and 4.62 mmHg for SBP and DBP. However, the optimum optimal feature sets provided by a genetic algorithm for estimating SBP/DBP led to the lowest mean absolute errors of 4.94/4.03. These results compared to previous studies and the available standards suggest that the method is a promising substitute for oscillometric sphygmomanometers which can be used conveniently for continuous monitoring of blood pressure.
关键词： Genetic algorithms,Non-obstructive blood pressure measurement,Multi-layer neural networks,Photo-plethysmography
更新于2025-09-23 15:23:52
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Fundamental Study on Blood Pressure Measurement by FBG Sensor
摘要： In recent years, the demands for vital sign measurement system have been increasing, such as home health care for elderly people, or self-health management for healthy people. In this study, we aimed at the development of a non-invasive wearable device to measure vital sign. We use a Fiber Bragg Grating (FBG) sensor as pulse wave sensor. A FBG sensor is the optical ?ber. Therefore, a FBG sensor has a lot of features. Its characteristics are suitable for the measurement of vital signs at all times. We ?x FBG sensors to di?erent two points of the body surface and acquired pulse wave. We calculated the systolic blood pressure by using Pulse Transit Time (PTT) which is arrival time lag of pulse wave. We have con?rmed the validity of the principle of systolic blood pressure measurement by FBG sensors.
关键词： wearable,blood pressure measurement,FBG sensor
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 3rd Advanced Information Technology, Electronic and Automation Control Conference (IAEAC) - Chongqing, China (2018.10.12-2018.10.14)] 2018 IEEE 3rd Advanced Information Technology, Electronic and Automation Control Conference (IAEAC) - Study on diaphragm Fabry-Perot pressure sensor
摘要： The manufacture method of the diaphragm Fabry-Perot(F-P) pressure sensor was studied. The sensor formed an F-P cavity by welding the hollow fiber on the end face of the single mode fiber, and manufactured a quartz diaphragm by cutting and grinding the single mode fiber. A new fitting demodulation method is proposed, which can obtain the FP cavity’s reflectivity, the diaphragm’s outside reflectivity, the F-P cavity length and the diaphragm thickness at one time. It is highly practical for the parameter monitoring in the sensor manufacturing process. Experiments show that the sensor has high sensitivity and linearity, and has great potential application value in the field of fluid mechanics measurement.
关键词： fiber optics,curve fitting,Pressure measurement,F-P interferometer,fiber sensor
更新于2025-09-19 17:15:36
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Fiber Bragg Grating-Based Oil-Film Pressure Measurement in Journal Bearings
摘要： The on-line measurement of oil-film pressure inside a journal bearing based on an optical fiber Bragg grating (FBG) is proposed and described for the first time. Two methods are described, one includes inserting the packaged FBG into the bearing using rubber and the other is involved the packaged FBG being directly embedded on the bearing surface. The inserted method has a higher sensitivity than the embedded version, while the embedded method incurs less damage to the bearing being small in size. Experiments to verify the feasibility of both methods are described with parameters being measured over the full motor operating range. Experimental results of the oil film pressure measured by these two methods agree well with simulated values, demonstrating excellent prospects for using the sensing schemes described in this paper as the basis for real industrial measurement systems. Furthermore, due to its small size and high sensitivity, coupled with excellent immunity to external electromagnetic interference the FBG sensor is an ideal candidate for measurement in which a strong electromagnetic field exists, e.g., in the case of electrical motors and generators.
关键词： temperature compensation,optical fiber sensors,oil film,pressure measurement,Fiber Bragg gratings (FBGs)
更新于2025-09-19 17:15:36
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Microelectromechanical system-based, high-finesse, optical fiber Fabry–Perot interferometric pressure sensors
摘要： A high-finesse, optical fiber, extrinsic Fabry–Perot interferometric (EFPI) pressure sensor based on a microelectromechanical system (MEMS) technique is proposed and experimentally demonstrated. The essential element in the pressure sensor is the high-finesse EFPI cavity that consists of a Pyrex glass wafer, a micromachined silicon wafer, and highly reflective dielectric films. Another Pyrex glass is used for fixing an optical fiber collimator, which allows the realization of the alignment of the incident light. Experimental results show that the proposed sensor exhibits a pressure sensitivity of 1.598 μm/MPa and a high-pressure sensing resolution of 0.002% of the full scale. This sensor is expected to benefit many applications that require high-accuracy pressure measurements, and especially atmospheric pressure applications.
关键词： optical fiber sensor,pressure measurement,microelectromechanical system,extrinsic Fabry–Perot interferometer
更新于2025-09-16 10:30:52
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[OSA Optical Fiber Sensors - Lausanne (2018..-..)] 26th International Conference on Optical Fiber Sensors - Fully distributed pressure sensing with ultra-high-sensitivity using side-hole fibers
摘要： A highly sensitive distributed pressure sensing system (< 20 hPa) based on phase sensitive optical time-domain reflectometry with side air holes fiber is proposed, reaching a sensing range of 1.05 km with a 5 cm spatial resolution.
关键词： Pressure measurement,Scattering, Rayleigh,Fiber optics sensors,Fiber optics
更新于2025-09-16 10:30:52
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Development of an optical pressure measurement system using an external cavity diode laser with a wide tunable frequency range
摘要： Optical pressure measurement systems can precisely measure pressure from vacuum to high pressure with a single apparatus. However, the continuously measurable range without interrupting measurement is limited to less than 1 kPa. In this study, an optical pressure measurement system with a wide continuous measurable range was developed. The optical system can continuously measure a pressure range of 18 kPa when using nitrogen gas by using a Littrow external cavity diode laser as its light source. First, discrete pressure points from vacuum to atmospheric pressure were measured. The repeatability and non-linearity of the differences between the measured values had standard deviations of 0.1 Pa and 0.5 Pa, respectively. Next, a pressure range from 91 kPa to 109 kPa was continuously measured. The results showed that the linearity characteristics of gauges as a function of pressure can be evaluated precisely using our optical pressure measurement system.
关键词： optical pressure measurement,external cavity diode laser,refractive index,wide tunable frequency range,Fabry-Perot cavity
更新于2025-09-12 10:27:22
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Towards a Quantum Standard for Absolute Pressure Measurements in the Range 200 Pa to 20 kPa Based on a Superconducting Microwave Cavity
摘要： We present a novel pressure standard for helium gas based on the measurement of resonance frequencies of a superconducting cavity and ab initio calculations of the thermophysical properties of helium. It should improve significantly the accuracy of measurements in the range 200 Pa to 20 kPa.
关键词： Microwave measurement,superconductivity,precision measurements,pressure measurement,frequency measurement
更新于2025-09-10 09:29:36
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Simultaneous measurements of temperature and pressure with a dual-cavity Fabry-Perot sensor
摘要： A fiber-optic dual-cavity Fabry-Perot interferometric sensor for the simultaneous measurement of temperature and pressure is proposed and experimentally demonstrated. The sensor cascades a fiber-optic intrinsic Fabry–Perot interferometer (IFPI) and an extrinsic Fabry–Perot interferometer (EFPI). The IFPI is used as the temperature sensor and the EFPI is used as the pressure sensor. The pressure sensor is based on a diaphragm-free structure, and can work stably at high temperature. Two optical path differences are interrogated simultaneously by using the fast Fourier transform-based white-light interferometry and the peak-to-peak method. Experimental results show that the proposed sensor exhibits a temperature sensitivity of 29.63 nm/°C within the temperature range of 40-1100 °C, and a pressure sensitivity of 1465.8 nm/MPa within the pressure range of 0-10 MPa at the room temperature.
关键词： pressure measurement,femtosecond laser micromachining,fiber optics sensors,Fabry-Perot interferometers,temperature measurement
更新于2025-09-04 15:30:14