Showing papers on "Pressure measurement published in 2020"

Simultaneous Measurement of Pressure and Temperature in Seawater with PDMS Sealed Microfiber Mach-Zehnder Interferometer

Abstract: Simultaneous measurement of pressure and temperature in seawater is realized based on polydimethylsiloxane (PDMS) sealed microfiber Mach–Zehnder interferometer (MZI). Benefitting from the high thermal-optic coefficient and large elasticity of PDMS, high sensitivity and robust structure can be obtained. In theoretical modeling, significant enhanced pressure response in fiber is observed clearly, and pressure or temperature sensitivities are calculated theoretically. In experiment, PDMS sealed MZI is fabricated by a two-step sealing method. Using this MZI, sensitivity of 13.31 nm/MPa for pressure sensing and −7.41 nm/°C for temperature sensing are demonstrated, respectively, which are about one order higher than bare fiber MZIs (without PDMS sealing). To verify the accuracy of sensor, several tests under arbitrarily pressure and temperature are performed with average errors of 4.38% and 1.44%, respectively. In addition, effects of encapsulation on avoiding cross-sensitivity with salinity, PDMS thickness on pressure sensitivity, response time, repeatability, time stability, and polarization of the sensor are also evaluated by experiment. Sensors demonstrated here show advantages of low cost, simple fabrication, robust and compact structure, high-pressure resistance, high sensitivity, good repeatability, and long-term stability.

Examination of the Performance Characteristics of Velostat as an In-Socket Pressure Sensor

Abstract: Velostat is a low-cost, low-profile electrical bagging material with piezoresistive properties, making it an attractive option for in-socket pressure sensing. The focus of this research was to explore the suitability of a Velostat-based system for providing real-time socket pressure profiles. The prototype system performance was explored through a series of bench tests to determine properties including accuracy, repeatability and hysteresis responses, and through participant testing with a single subject. The fabricated sensors demonstrated mean accuracy errors of 110 kPa and significant cyclical and thermal drift effects of up to 0.00715 V/cycle and leading to up to a 67% difference in voltage range respectively. Despite these errors the system was able to capture data within a prosthetic socket, aligning to expected contact and loading patterns for the socket and amputation type. Distinct pressure maps were obtained for standing and walking tasks displaying loading patterns indicative of posture and gait phase. The system demonstrated utility for assessing contact and movement patterns within a prosthetic socket, potentially useful for improvement of socket fit, in a low cost, low profile and adaptable format. However, Velostat requires significant improvement in its electrical properties before proving suitable for accurate pressure measurement tools in lower limb prosthetics.

Simultaneous measurement of acoustic pressure and temperature using a Fabry-Perot interferometric fiber-optic cantilever sensor

Abstract: A Fabry-Perot (F-P) interferometric fiber-optic cantilever sensor is presented for simultaneous measurement of acoustic pressure and temperature, which are demodulated by a single high-speed spectrometer. The acoustic pressure wave pushes the cantilever to produce periodic deflection, while the temperature deforms the sensor and causes the F-P cavity length to change slowly. The absolute length of the F-P cavity of the fiber-optic cantilever sensor is calculated rapidly by using a spectral demodulation method. The acoustic pressure and temperature are obtained by high-pass filtering and averaging the continuously measured absolute cavity length value, respectively. The experimental results show that the acoustic pressure can be detected with an ultra-high sensitivity of 198.3 nm/Pa at 1 kHz. In addition, an increase in temperature reduces the resonant frequency of the acoustic response and increases the static F-P cavity length. The temperature coefficient of the resonance frequency shift and the temperature response of the sensor are -0.49 Hz/°C and 83 nm/°C, respectively. Furthermore, through temperature compensation, the measurement error of acoustic pressure reaches ± 3%. The proposed dual parameter measurement scheme greatly simplifies the system structure and reduces the system cost.

Reflected Near-field Blast Pressure Measurements Using High Speed Video

Abstract: Background: The design and analysis of protective systems requires a detailed understanding of, and the ability to accurately predict, the distribution of pressure loads acting on an obstacle following an explosive detonation In particular, there is a pressing need for accurate characterisation of blast loads in the region very close to a detonation, where even small improvised devices can produce serious structural or material damage Objective: Accurate experimental measurement of these near-field blast events, using intrusive methods, is demanding owing to the high magnitudes (> 100 MPa) and short durations (< 1 ms) of loading The objective of this article is to develop a non-intrusive method for measuring reflected blast pressure distributions using image analysis Methods: This article presents results from high speed video analysis of near-field spherical PE4 explosive blasts The Canny edge detection algorithm is used to track the outer surface of the explosive fireball, with the results used to derive a velocity-radius relationship Reflected pressure distributions are calculated using this velocity-radius relationship in conjunction with the Rankine-Hugoniot jump conditions Results: The indirectly measured pressure distributions from high speed video are compared with directly measured pressure distributions and are shown to be in good qualitative agreement with respect to distribution of reflected pressures, and in good quantitative agreement with peak reflected pressures (within 10% of the maximum recorded value) Conclusions: The results indicate that it is possible to accurately measure blast loads in the order of 100s MPa using techniques which do not require sensitive recording equipment to be located close to the source of the explosion

A Simple, Highly Sensitive Fiber Sensor for Simultaneous Measurement of Pressure and Temperature

Abstract: A simple, highly sensitive fiber Fabry-Perot interference sensor based on polydimethylsiloxane (PDMS) is proposed and demonstrated for simultaneous measurement of gas pressure and temperature. The sensor is fabricated by fusion splicing a short segment of hollow capillary tube to a standard single mode fiber and injecting PDMS in sections into capillary tube, then three reflecting surfaces are formed. Experimental results show that sensitivities of temperature and gas pressure are 2.62 nm/°C and 20.63 nm/MPa, respectively. The proposed sensor has advantages of compact size, low cost, robust structure, easy fabrication, and it is applicable to real sensing application.

Miniature fiber-optic tip pressure sensor assembled by hydroxide catalysis bonding technology.

Abstract: A miniature fiber-optic tip Fabry-Perot (FP) pressure sensor with excellent high-temperature survivability, assembled by hydroxide catalysis bonding (HCB) technology, is proposed and experimentally demonstrated. A standard single-mode fiber is fusion spliced to a fused silica hollow tube with an outer diameter (OD) of 125 µm, and a 1-µm-thick circular silicon diaphragm with a diameter slightly larger than the OD is bonded to the other endface of the hollow tube by HCB technology. The ultrathin silicon diaphragm is prepared on a silicon-on-insulator (SOI) wafer produced by microelectromechanical systems (MEMS), providing the capability of large-scale mass production. The HCB technology enables a polymer-free bonding between diaphragm and hollow tube on fiber tip with the obvious advantages of high alignment precision, normal pressure and temperature (NPT) operation, and reliable effectiveness. The static pressure and temperature response of the proposed sensor are discussed. Results show that the sensor has a measurable pressure range of 0∼100 kPa, which is well consistent with the measurement range of biological blood pressure. The pressure sensitivity is up to 2.13 nm/kPa with a resolution of 0.32% (0.32kPa). Besides, the sensor possesses a unique high-temperature resistant capability up to 600 °C, which can easily survive even in high-temperature sterilization processes, and it has a low temperature dependence of 0.09 kPa/°C due to the induced HCB bonding technology and the silicon-based diaphragm. Thus, the proposed fiber tip pressure sensor is desirable for invasive biomedical pressure diagnostics and pressure monitoring in related harsh environments.

Microelectromechanical system-based, high-finesse, optical fiber Fabry–Perot interferometric pressure sensors

Abstract: 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.

Isolator characteristics under steady and oscillatory back pressures

Abstract: Experiments are carried out to characterize the un-start/re-start phenomena in an isolator with steady and low-frequency oscillatory back pressures (0.75 Hz–2.5 Hz) in Mach 1.7 flow. In the present study, the effect of shock train interaction with the intake shocks is focused to capture these phenomena. It is demonstrated that the un-start mechanism is a continuous process with steady back pressures, whereas it is a discontinuous process under oscillatory back pressures. The un-start mechanism is triggered once the oscillatory back pressure is above the maximum isolator pressure. As the frequency of back pressure oscillation is increased, the isolator experiences an early un-start and a delayed re-start. On the other hand, if the oscillatory back pressure is decreased, the re-start process is initiated. During the re-start process, the time lag is found to be increased, and the hysteresis loss is decreased with an increase in oscillatory frequencies. These phenomena are studied through both the steady and unsteady pressure measurements along with instantaneous schlieren images for different dynamic pressures. Furthermore, the un-start can be avoided or delayed by increasing the freestream dynamic pressure.

Novel resonant pressure sensor based on piezoresistive detection and symmetrical in-plane mode vibration.

Abstract: In this paper, a novel resonant pressure sensor is developed based on electrostatic excitation and piezoresistive detection. The measured pressure applied to the diaphragm will cause the resonant frequency shift of the resonator. The working mode stress–frequency theory of a double-ended tuning fork with an enhanced coupling beam is proposed, which is compatible with the simulation and experiment. A unique piezoresistive detection method based on small axially deformed beams with a resonant status is proposed, and other adjacent mode outputs are easily shielded. According to the structure design, high-vacuum wafer-level packaging with different doping in the anodic bonding interface is fabricated to ensure the high quality of the resonator. The pressure sensor chip is fabricated by dry/wet etching, high-temperature silicon bonding, ion implantation, and wafer-level anodic bonding. The results show that the fabricated sensor has a measuring sensitivity of ~19 Hz/kPa and a nonlinearity of 0.02% full scale in the pressure range of 0–200 kPa at a full temperature range of −40 to 80 °C. The sensor also shows a good quality factor >25,000, which demonstrates the good vacuum performance. Thus, the feasibility of the design is a commendable solution for high-accuracy pressure measurements. The operating principle and experimental realization of a new piezoresistive resonant pressure sensor are shown. Resonant pressure sensors rely on changes in applied pressure to a diaphragm to cause the resonant frequency of the resonator to change. This enables high stability and signal-to-noise ratios, combined with a quasi-digital output; resultantly, resonant pressure sensors are often used in critical applications such as aerospace and for instrument calibration. Here, a team led by Zhuangde Jiang from Xi’an Jiaotong University, China, report a piezoresistive detection-based resonant pressure sensor. They establish the theory for their device operation, verified by both simulations and experiments. Their device shows an accuracy better than 0.02% FS and a resonant quality factor greater than 25,000.

Sapphire Fabry-Perot interferometer for high-temperature pressure sensing.

Abstract: An adhesive-free encapsulation sapphire Fabry–Perot interferometer (FPI) is proposed and demonstrated for high-temperature pressure measurements. The sapphire FPI sensor is packaged by zirconia ferrules and a zirconia sleeve, which is easy to be configured and low in cost. Owing to this packaging technology, the sapphire FPI sensor presents good stability and high temperature resistance. The pressure and temperature properties of the sapphire FPI sensor are investigated within a temperature range from −50∘C to 1200°C and a pressure range from 0.4 to 4.0 MPa. Experimental results show the FPI has a temperature sensitivity of 23 pm/°C and still works as the temperature is up to 1200°C. Meanwhile, the wavelength shift of the sapphire FPI versus the applied pressure is linear at each tested temperature. The pressure sensitivity is measured to be 1.20 nm/MPa at 1200°C, and the linear response shows the proposed sensor has good repeatability within 0.4–4.0 MPa. Such a sapphire FPI sensor has potential applications in engineering areas, such as the oil industry and gas boilers.

4D Flow MRI Pressure Estimation Using Velocity Measurement-Error-Based Weighted Least-Squares

Abstract: This work introduces a 4D flow magnetic resonance imaging (MRI) pressure reconstruction method which employs weighted least-squares (WLS) for pressure integration. Pressure gradients are calculated from the velocity fields, and velocity errors are estimated from the velocity divergence for incompressible flow. Pressure gradient errors are estimated by propagating the velocity errors through Navier-Stokes momentum equation. A weight matrix is generated based on the pressure gradient errors, then employed for pressure reconstruction. The pressure reconstruction method was demonstrated and analyzed using synthetic velocity fields as well as Poiseuille flow measured using in vitro 4D flow MRI. Performance of the proposed WLS method was compared to the method of solving the pressure Poisson equation which has been the primary method used in the previous studies. Error analysis indicated that the proposed method is more robust to velocity measurement errors. Improvement on pressure results was found to be more significant for the cases with spatially-varying velocity error level, with reductions in error ranging from 50% to over 200%. Finally, the method was applied to flow in patient-specific cerebral aneurysms. Validation was performed with in vitro flow data collected using Particle Tracking Velocimetry (PTV) and in vivo flow measurement obtained using 4D flow MRI. Pressure calculated by WLS, as opposed to the Poisson equation, was more consistent with the flow structures and showed better agreement between the in vivo and in vitro data. These results suggest the utility of WLS method to obtain reliable pressure field from clinical flow measurement data.

Conformable, programmable and step-linear sensor array for large-range wind pressure measurement on curved surface

Abstract: The wind pressure measurement, especially on curved surfaces is imperative in revealing flow characteristics. The flexible sensor with high linear sensitivity over large pressure range is still a significant challenge, especially for commutatively positive and negative pressure measurement. Here, we propose a conformable, range-programmable capacitive sensor that can extremely extend the measuring range but with high linear sensitivity. The key point is to precisely control the reference pressure of the flexible capacitive sensor array through microchannel network. The proposed sensor with reference pressure 0 kPa keeps stable at a highly-linear sensitivity of 0.28 kPa−1 in an initial measurement regime from 0 to 3 kPa, beyond which the linearity changes significantly. Via the tunable reference pressure, the linear ranges can be customized arbitrarily according to different flight conditions and measured positions, but without any deterioration of sensitivity. The theoretical model is built for the flexible capacitive sensor with tunable reference pressure, agreeing well with the experimental and finite element method results. Additionally, the bending effect is discovered when the flexible sensor is conformed on curved surfaces. This surface-mounted sensor skin is tested on a plate and is integrated with acquisition circuits on a standard airfoil NACA0012 in a wind tunnel and compares with the standard destructive method of pressure taps. It shows great potential applications in measuring wind pressure on curved surfaces, such as for “Fly-by-Feel” of unmanned aerial vehicles and wind tunnel test.

Characterization and analysis of a novel structural SOI piezoresistive pressure sensor with high sensitivity and linearity

Abstract: A novel structural piezoresistive pressure sensor with four-grooved diaphragm combined with rood beam has been proposed for low pressure measurements of less than 1 psi. The proposed sensor chip is fabricated on a SOI wafer by traditional MEMS micromachining and anodic bonding technology. By localizing more strain energy in the stress concentration region and increasing the constraint of the partial pedestal, the sensor achieved a high sensitivity and linearity of 30.9 mV/V/psi and 0.25% FSS respectively at room temperature, and thereby the contradiction between sensitivity and linearity is alleviated. Besides, a sensitivity of 21.2 mV/V/psi and a linearity of 0.5% FSS were obtained at 150 °C, which illustrates that the proposed sensor has a stable high temperature output characteristic. Additionally, the mechanisms about strain energy transmission and partially stiffened diaphragm are also discussed.

Early Tsunami Detection With Near-Fault Ocean-Bottom Pressure Gauge Records Based on the Comparison With Seismic Data

Abstract: Offshore real-time ocean bottom networks of seismometers and ocean bottom pressure (OBP) gauges have been recently established such as DONET and S-net around the Japanese islands. One of their purposes is to practice rapid and accurate tsunami forecasting. Near-fault OBP records, however, are always contaminated by nontsunami components such as sea-bottom acceleration change until an earthquake stops its fault or sea-floor motions. This study proposes a new method to separate tsunami and ocean bottom displacement components from coseismic OBP records in a real-time basis. Associated with the Off-Mie earthquake of 2016 April 1, we first compared OBP data with acceleration, velocity, and displacement seismograms recorded by seismometers at common ocean bottom sites in both time and frequency domains. Based on this comparison, we adopted a band-pass filter of 0.05–0.15 Hz to remove ocean-bottom acceleration components from the OBP data. Resulting OBP waveforms agree well with the tsunami components estimated by a 100-s low-pass filter with records of several hundred seconds in length. Our method requires only an early portion of a given OBP record after 30 s of an origin time in order to estimate its tsunami component accurately. Our method enhances early tsunami detections with near-fault OBP data; that is, it will make a tsunami forecasting system faster and more reliable than the previous detection schemes that require data away from source regions or after coseismic motions are over. Plain Language Summary Offshore real-time ocean bottom networks of seismometers and ocean bottom pressure (OBP) gauges have been recently established around the Japanese island. One of their purpose is to realize rapid and accurate tsunami forecasting by near-fault observations. Near-fault OBP records, however, are contaminated by nontsunami components such as sea-bottom acceleration change (i.e., reaction force from the water column above a station), permanent sea-bottom deformation, and ocean acoustic waves or P waves. This study proposes a new real-time method to separate tsunami and sea-bottom displacement components from near-fault OBP records. Our method enables to detect tsunamis accurately with near-fault OBP data only after 30 s of an origin time. Issuing an accurate and rapid tsunami warning with the present method will contribute to significant reduction of tsunami-related casualties.

Using uncertainty to improve pressure field reconstruction from PIV/PTV flow measurements

Abstract: A novel pressure reconstruction method is proposed to use the uncertainty information to improve the instantaneous pressure fields from velocity fields measured using particle image velocimetry (PIV) or particle tracking velocimetry (PTV). First, the pressure gradient fields are calculated from velocity fields, while the local and instantaneous pressure gradient uncertainty is estimated from the velocity uncertainty using a linear-transformation-based algorithm. The pressure field is then reconstructed by solving an overdetermined linear system which involves the pressure gradients and boundary conditions. This linear system is solved with generalized least squares (GLS) which incorporates the previously estimated variances and covariances of the pressure gradient errors as inverse weights to optimize the reconstructed pressure field. The method was validated with synthetic velocity fields of a 2D pulsatile flow, and the results show significantly improved pressure accuracy. The pressure error reduction by GLS was 50% with 9.6% velocity errors and 250% with 32.1% velocity errors compared to the existing baseline method of solving the pressure Poisson equation (PPE). The GLS was more robust to the velocity errors and provides greater improvement with spatially correlated velocity errors. For experimental validation, the volumetric pressure fields were evaluated from the velocity fields measured using 3D PTV of a laminar pipe flow with a Reynolds number of 630 and a transitional pipe flow with a Reynolds number of 3447. The GLS reduced the median absolute pressure errors by as much as 96% for the laminar pipe flow compared to PPE. The mean pressure drop along the pipe predicted by GLS was in good agreement with the empirical estimation using Darcy–Weisbach equation for the transitional pipe flow.

Matrix-Addressed Flexible Capacitive Pressure Sensor With Suppressed Crosstalk for Artificial Electronic Skin

Abstract: Matrix-addressed flexible pressure sensors, being able to accurately measure both local contact force and spatial distribution, are pursued for many electronic skin applications. One key issue to be addressed is that the local force being applied onto the target areas may be passed to the neighboring pixels through deformation of the touched top electrode layer. It causes significant signal crosstalk and also loss of measurement accuracy. A new top electrode layer structure is proposed with the development of processes for matrix-addressed pressure sensor systems. It is composed of a patterned layer of high Young’s modulus and a low-modulus encapsulation layer. The former is able to sustain a relatively high processing temperature for forming reliable and high-density electrical connections. The latter is to protect the patterned layer while having low Young’s modulus to minimize the spreading of local deformation at the pressed pixel to the surrounding ones. A $10 \times 10$ matrix-addressed flexible capacitive pressure sensor system is constructed to verify this design, showing effective suppression of the pixel-to-pixel signal crosstalk and improvement of measurement accuracy. The flexible pressure sensor system is integrated onto a prosthetic hand, showing capabilities of differentiating details of massage balls.