Showing papers on "Pressure measurement published in 2022"

High-Pressure Sensor With High Sensitivity and High Accuracy for Full Ocean Depth Measurements

Abstract: Ocean depth measurement is very important for ocean observation, prediction and development. In this work, an absolute piezoresistive pressure sensor with high sensitivity and high accuracy for full ocean depth measurement is designed and fabricated through theoretical calculations and simulations. The shape and dimension of the diaphragm are designed through finite element simulation. A thick circular C-type diaphragm is used and the stress distribution on the diaphragm is simulated. The influence of the shape, dimension and position of the piezoresistors on the sensitivity and nonlinearity is calculated and analyzed, and the performance of sensors with single-bar-shaped piezoresistors and sensors with meander-shaped piezoresistors with different spacing is further compared. A tri-meanders-shaped piezoresistor with a large ratio of piezoresistance to connecting layer resistance is designed, and the piezoresistor position with high linearity is determined through simulation. Non-glue oil-filled isolation package is used to improve the repeatability and hysteresis of the sensor. The pressure sensor has a range of 0–120 MPa, a sensitivity of 0.425 mV/V/MPa, and an accuracy of 0.0182 %FS.

Experimental Measurements of Equivalent Available Pressure - Lessons Learned

Abstract: For the past several years, AFRL has been making equivalent available pressure measurements in rotating detonation engines. EAP is currently the leading candidate to make performance measurements in an RDE, allowing comparisons to traditional, steady combustors. This paper goes over the lessons learned and the methodologies developed to make EAP measurements on laboratory-scale RDEs. Sensor placement, measurement uncertainty, and calculation methods are discussed and best practices recommended.

Singlemode-Multimode-Singlemode Optical Fiber Sensor for Accurate Blood Pressure Monitoring

Abstract: A dual-channel single-mode-multi-mode-single-mode (SMS) fiber optic sensor encapsulated by polydimethylsiloxane (PDMS) was proposed for the first time, for the simultaneous monitoring of the brachial and radial arteries for accurate blood pressure prediction. With the help of the machine learning algorithm Support Vector Regression (SVR), the SMS fiber sensor can continuously and accurately monitor the systolic and diastolic blood pressure. Commercial sphygmomanometers are used to calibrate the accuracy of blood pressure measurement. Compared with the single-channel system, this system can extract more pulse wave features for blood pressure prediction, such as radial artery transit time (RPTT), brachial artery transit time (BPTT), and the transit time difference between the radial artery and the brachial artery (DBRPTT). The results show that the performance of dual-channel blood pressure monitoring is more accurate than that of single-channel blood pressure monitoring in terms of the absolute value of the correlation coefficient (R) and the average value of the difference between SBP and DBP. In addition, both the single-channel and dual-channel blood pressure monitoring are in line with the Association for the Advancement of Medical Devices (AAMI), but the average deviation (DM, 0.06 mmHg) and standard deviation (SD, 1.54 mmHg) of dual-channel blood pressure monitoring are more accurate. The blood pressure monitoring system has the characteristics of low cost, high sensitivity, non-invasive and capability for remote real time monitoring, which can provide effective solution for intelligent health monitoring in the era of artificial intelligence in the future.

Sensitivity of Piezoresistive Pressure Sensors to Acceleration

Abstract: The article presents the negative aspects of the influence of static and dynamic acceleration on the accuracy of pressure measurement for a selected type of transmitter. The influence of static accelerations from catalog notes was shown and compared with the tests results for a few selected sensors. The results of research on the influence of dynamic acceleration for various types of its variability for selected converters are presented. Moreover, a method of measurement patented by the authors that uses a complex transducer is shown. The method allows for more accurate measurements on moving objects. The tests were performed based on the proposed method. The obtained results of the influence of acceleration on the classical sensor as well as the construction using the proposed method are shown. The paper presents approximate pressure measurement errors resulting from the influence of acceleration. For example, errors in measuring the speed of an airplane may occur without the proposed method. The last part of the article presents a unique design dedicated to a multi-point pressure measurement system, which uses the presented method of eliminating the influence of accelerations on the pressure measurement.

Visualization of Pressure and Skin-Friction Fields on Rotating Blade Under Low-Pressure Conditions

Abstract: Distributions of the pressure and mass transfer coefficient on rotating blades under low-pressure (low-Reynolds-number) conditions were visualized, whereas the latter is closely related to the skin-friction distribution. Two types of optical measurement techniques, lifetime-based pressure-sensitive paint (PSP) measurements and sublimation visualization, were implemented for the experiment inside a low-pressure chamber. For the lifetime-based PSP measurement, different types of PSP were compared, and the one most suitable in low-pressure applications was selected. In addition, the gate time setting for the low-pressure condition was determined. For the sublimation method, naphthalene was selected as the sublimation surface based on previous studies. The rotating blade test model was a 0.3-m-diam rotor system with two rectangular blades with an aspect ratio of two. The experiments were carried out at a rotational speed of 2400 rpm and at an ambient pressure of 10 kPa. The three-fourth-span Reynolds number was 9000. The pitch angle of the blades was set to 0–20 deg. Both methods successfully illustrated clear images of the distribution of pressure and mass transfer coefficients on the upper surface of the blade, and the measurement in the low-pressure environment was successful.

A Compact Optical MEMS Pressure Sensor Based on Fabry–Pérot Interference

Abstract: Pressure sensors have important prospects in wind pressure monitoring of transmission line towers. Optical pressure sensors are more suitable for transmission line towers due to its anti-electromagnetic interference. However, the fiber pressure sensor is not a suitable choice due to expensive and bulky. In this paper, a compact optical Fabry–Pérot (FP) pressure sensor for wind pressure measurement was developed by MEMS technology. The pressure sensor consists of a MEMS sensing chip, a vertical-cavity surface-emitting laser (Vcsel), and a photodiode (PD). The sensing chip is combined with an FP cavity and a pressure sensing diaphragm which adopts the square film and is fabricated by Silicon on Insulator (SOI) wafer. To calibrate the pressure sensor, the experimental platform which consists of a digital pressure gauge, a pressure loading machine, a digital multimeter, and a laser driver was set up. The experimental results show that the sensitivity of the diaphragm is 117.5 nm/kPa. The measurement range and sensitivity of the pressure sensor are 0–700 Pa and 115 nA/kPa, respectively. The nonlinearity, repeatability, and hysteresis of the pressure sensor are 1.48%FS, 2.23%FS, and 1.59%FS, respectively, which lead to the pressure accuracy of 3.12%FS.

Towards traceable dynamic pressure calibration using a shock tube with an optical probe for accurate phase determination

Abstract: In this paper, we introduce a robust method for dynamic characterization of pressure measuring systems used in time-varying pressure applications. The dynamic response of the pressure measuring systems in terms of sensitivity and phase as a function of frequency at various amplitudes of the measurand can be provided. The shock tube which is the candidate primary standard for dynamic pressure calibration at the National Laboratory for pressure, Sweden, was used to realize the dynamic pressure. The shock tube setup used in this study can realize reference pressure with amplitudes up to 1.7 MPa in the frequency range from below a kilohertz up to a megahertz. The amplitude of the realized step pressure was calculated using the Rankine–Hugoniot step relations. In addition, the accurate time of arrival of the generated shock at the device under test (DUT) was measured using an optical probe based on shadowgraphy. The optical detector has a response time in nanosecond time scale which is several orders of magnitude faster than the response time of any pressure measuring system. Hereby, the latency between physical stimuli and response of the DUT can be measured. By the knowledge of the amplitude and the accurate time of arrival of the reference step pressure, the transfer function of the DUT can be calculated and presented in Bode diagrams of sensitivity and phase response versus frequency. The uncertainty in sensitivity and phase measurements was estimated. The information provided by this work is useful for developing reliable models of dynamic pressure measuring system and provide accurate information about their dynamic response. That in turn will contribute to establish a traceability chain for dynamic pressure calibration.

Fibre Bragg Grating Based Interface Pressure Sensor for Compression Therapy

Abstract: Compression therapy is widely used as the gold standard for management of chronic venous insufficiency and venous leg ulcers, and the amount of pressure applied during the compression therapy is crucial in supporting healing. A fibre optic pressure sensor using Fibre Bragg Gratings (FBGs) is developed in this paper to measure sub-bandage pressure whilst removing cross-sensitivity due to strain in the fibre and temperature. The interface pressure is measured by an FBG encapsulated in a polymer and housed in a textile to minimise discomfort for the patient. The repeatability of a manual fabrication process is investigated by fabricating and calibrating ten sensors. A customized calibration setup consisting of a programmable translation stage and a weighing scale gives sensitivities in the range 0.4–1.5 pm/mmHg (2.6–11.3 pm/kPa). An alternative calibration method using a rigid plastic cylinder and a blood pressure cuff is also demonstrated. Investigations are performed with the sensor under a compression bandage on a phantom leg to test the response of the sensor to changing pressures in static situations. Measurements are taken on a human subject to demonstrate changes in interface pressure under a compression bandage during motion to mimic a clinical application. These results are compared to the current gold standard medical sensor using a Bland–Altman analysis, with a median bias ranging from −4.6 to −20.4 mmHg, upper limit of agreement (LOA) from −13.5 to 2.7 mmHg and lower LOA from −32.4 to −7.7 mmHg. The sensor has the potential to be used as a training tool for nurses and can be left in situ to monitor bandage pressure during compression therapy.

Sensitivity-Photo-Patternable Ionic Pressure Sensor Array with a Wearable Measurement Unit.

Abstract: A flexible pressure sensor array provides more information than a single pressure sensor as electronic skin, and independently definable sensitivities of sensing pixels enable more accurate pressure measurements. However, the reported approaches, either changing the mold for the dielectric layer or tuning the dielectric properties, overcomplicate the manufacturing process for the devices. Here, we present a pressure sensor array with photo-patterned sensitivity, which is realized through the synergistic creation of the photo-defined mechanical properties of the dielectric layer and the interfacial capacitive sensing mechanism. Via this design, the sensitivity of each sensing pixel can be photo-defined over a range of ∼70 times of magnitude. Additionally, we created the first wearable measurement unit for the ionic pressure sensor array. The sensitivity-photo-patternable pressure sensor array and the wearable measurement unit fulfill the open need of mapping the pressure distribution over a broad range of magnitude, such as the plantar pressure.

A Portable Insole System to Simultaneously Measure Plantar Pressure and Shear Stress

Abstract: Objective: This work aims to develop an integrated in-shoe measurement system to fully record plantar loading, including both pressure and shear stresses, across the full contact surface. These data are vital to help understand and prevent the development of complex conditions such as Diabetic Foot Ulcers (DFUs), a worldwide healthcare challenge. Currently no systems exist to reliably record these data. Methods: In this paper we report development of the SLIPS (‘Shear Load Inductive Plantar Sensing’) system which integrates 64 tri-axial force sensors into a flexible insole to measure plantar loading. SLIPS translates our multi-axis inductive load sensing technology into a full sensory array embedded within an insole and complete with communication and power bus. A pilot study evaluates the system in three healthy participants during walking. Results: Testing shows that the SLIPS system is well tolerated by participants and can operate under dynamic gait loading regimes. The pilot study reveals the complex nature of plantar loading. Regions of peak pressure loading align with anatomical landmarks and shear loading forms a significant component of the overall load. Notably, regions of peak shear and pressure are not necessarily collocated or present in unison. Conclusion: This work highlights the need for in-shoe plantar measurement systems like SLIPS capable of mapping both pressure and shear load, and their use to improve understanding of how these factors relate to clinical conditions like DFU. Significance: SLIPS represents the first in-shoe measurement system capable of measuring both pressure and shear across the whole plantar surface in unison.

Simultaneous measurement of pressure and temperature in a supersonic ejector using FBG sensors

Abstract: In this work, we have demonstrated the use of fiber Bragg grating (FBG) sensors for simultaneous measurement of wall static pressure and temperature in a supersonic ejector. Supersonic ejectors are ground-based high-speed aerodynamic test facilities characterized by harsh conditions, such as high pressure and temperature gradients. An FBG-based sensor setup was developed consisting of a pressure measuring bare FBG and a specially designed pressure-insensitive FBG temperature probe that can be mounted on the wall of the supersonic ejector. The FBG temperature probe was used for temperature measurement as well as temperature compensation of the pressure measuring FBG sensor. Wall static pressure measurements in the supersonic ejector were carried out at different tank pressures and Mach number flows. The FBG pressure measurements were validated with those of standard piezoresistive-based sensor measurements. Both responses were found to match closely, with FBG sensors having a faster response time and higher pressure resolution. Fluid structure interaction simulation was carried out in Comsol Multiphysics to understand the interaction of high-speed turbulent flow with FBG sensor. The FBG strain profile due to flow-induced stress and its dependence on flow pressure was studied. A detailed analysis of the effect of preceding fiber length on FBG pressure measurement was carried out. FBG sensors, due to their miniature size, ability to withstand harsh environments and multi-parameter sensing capability, can be used in ground-based aerodynamic test facilities with minimal intrusion into the flow.

Experimental Assessment of Cuff Pressures on the Walls of a Trachea-Like Model Using Force Sensing Resistors: Insights for Patient Management in Intensive Care Unit Settings

Abstract: The COVID-19 outbreak has increased the incidence of tracheal lesions in patients who underwent invasive mechanical ventilation. We measured the pressure exerted by the cuff on the walls of a test bench mimicking the laryngotracheal tract. The test bench was designed to acquire the pressure exerted by endotracheal tube cuffs inflated inside an artificial model of a human trachea. The experimental protocol consisted of measuring pressure values before and after applying a maneuver on two types of endotracheal tubes placed in two mock-ups resembling two different sized tracheal tracts. Increasing pressure values were used to inflate the cuff and the pressures were recorded in two different body positions. The recorded pressure increased proportionally to the input pressure. Moreover, the pressure values measured when using the non-armored (NA) tube were usually higher than those recorded when using the armored (A) tube. A periodic check of the cuff pressure upon changing the body position and/or when performing maneuvers on the tube appears to be necessary to prevent a pressure increase on the tracheal wall. In addition, in our model, the cuff of the A tube gave a more stable output pressure on the tracheal wall than that of the NA tube.

A Packaging Technique of Pressure Sensor for In Vivo Measurement System

Abstract: Bodily pressures can provide valuable information for making a diagnosis or health monitoring. The pressure sensor is widely used to obtain bodily pressure, however, sensor drift has severely limited their application in vivo measurement system. In this paper, we report on a packaging technique for improving the stability and accuracy of the pressure sensor. Commercial piezoresistive pressure sensors are enclosed in silicone oil and then encapsulated with silicone membrane and parylene-N. The described method isolates the pressure sensor from the abominable surrounding environment and keeps the pressure in the cavity constant. In vitro tests for 40 days show that the pressure sensor packaged by this method could obtain better stability. The average baseline drift of the pressure sensor was 0.025 mmHg/week after the pressure sensor became stable.

An all-fiber diaphragm-based extrinsic Fabry–Perot sensor for the measurement of pressure at ultra-low temperature

Abstract: An all-fiber diaphragm-based extrinsic Fabry–Perot interferometer (EFPI) sensor for the measurement of pressure at ultra-low temperature is proposed and experimentally demonstrated. The sensor head is manufactured at the end of a single mode fiber with a micro hole and a fiber diaphragm. By femtosecond (fs) laser micromachining, sensors with different sensitivities can be fabricated with different diameter of the micro hole and different thickness of the diaphragm. The deformation of the diaphragm has a linear relationship with the applied pressure. This EFPI is used to measure the pressure at temperature of −196 °C by monitoring the cavity length of the interferometer. Experiment results show the sensor exhibits good linearity within a pressure range from 0 to 7 MPa, and the pressure sensitivities at −196 °C during the process of pressure increasing and decreasing are 111.17 and 111.22 nm MPa−1, respectively. The proposed all-fiber pressure sensor can find applications in ultra-low temperature environment.

Single pressure transducer probe for 3D flow measurements

Abstract: A new method of measuring 3D flow with a single pressure transducer mounted inside the head of a single probe is presented in this paper. The 3D flow field around the hemispherical or ellipsoidal probe head is used to derive the 3D flow vector in virtual 5-sensor mode. A pressure tap located in the vicinity of the probe head connects the instantaneous pressure of the measurement volume to the pressure transducer. By turning the probe to five different positions around the axis of the stem, a set of five pressures is formed. The relevant flow parameters such as total and static pressure, yaw and pitch angle as well as Mach number are derived from these five pressures using the proposed calibration model. A selection of six different probe head geometries with different pressure tap positions have been manufactured and calibrated in a free jet facility in order to find the ideal probe geometry. The results of the steady probe calibration showed that the probe captures 3D flow at a slightly higher error band compared to other probe techniques such as pneumatic multiple hole probes. A summary of the achieved model accuracy for each probe is given. Finally, the calibration model can be extended to any single sensor cylindrical probe, provided that the pressure coefficient shows a measurable variation with pitch angle.

Simultaneous Measurement of Water Pressure and Temperature Based on a Simple Fabry-Pérot Sensor

Abstract: We proposed a simple and compact Fabry-Perot (FP) sensor for simultaneous measurement of water pressure and temperature, composed of a standard fiber ferrule connector/flat contact (FC/FC) connector and aluminum foil attached to a thin metal plate. Two dips in the interference spectrum are selected to illustrate the response of the FP sensor to the water pressure and temperature, we can obtain the simultaneous measurement via a method of sensitivity coefficient matrix. Experimental results show the maximum sensitivity of −2.948 nm/kPa for water pressure sensing in 0~9 kPa and 1.119nm/°C for temperature sensing in 33~45 °C. In addition, the dual-parameter sensor has the advantages of compactness, stability, simple production, small size, and high sensitivity, making it suitable for a wide range of practical applications.

Optical fiber Fabry-Perot silica-microprobe for a gas pressure sensor

Abstract: An all-fiber Fabry-Perot microprobe gas pressure sensor based on the femtosecond (fs) laser micromachining technology is proposed and demonstrated. The protruding-shaped silica-microprobe is spliced on the tip of the single mode fiber (SMF), and the gas microcavity is fabricated by the fs laser to form the Fabry-Perot interferometer (FPI), and the machining accuracy of the gas microcavity is better than 2 μm. The length of silicon-microprobe is less than 150 μm and its diameter is less than 30 μm, and the length of gas microcavity in microprobe is about 52 μm. The third reflective surface is formed at the junction between the microprobe and the SMF, the vernier effect can be cleverly utilized to improve the sensitivity of gas pressure. The experiment results indicate that the microprobe FPI gas pressure sensor has a sensitivity of 16.3536 nm/MPa with the increase of gas pressure, and a sensitivity of temperature is only 0.0043 nm/°C from 30 °C to 100 °C. The gas pressure sensor has the advantages of small size, high gas pressure sensitivity and low cross-sensitivity of temperature, and is expected to be applied in the special field, such as detection of gas pressure in alveoli.

Effect of sensor installation angle on measurement of explosion shock wave pressure

Abstract: The inclination of a shock wave pressure sensor with respect to the ground has been reported to have a significant effect on the accuracy of the measured shock wave pressure. Extensive research is required for the planning of damage power test site layouts and improvement of the accuracy of blast shock wave pressure tests. Thus, in this study, we established a three-dimensional numerical simulation model based on a real shooting range test site and investigated the effects of various sensor installation angles and measurement point distances on the shock wave overpressure via multi-point modeling. Overpressure data and pressure evolution contour plots were generated from seven sensor installation angles and six measurement points. Overpressure–time history curves, peak overpressure decay rates, and relative change in the peak overpressure with the installation angle were analyzed to investigate the effects of the sensor installation angle on the pressure test. The data obtained from the numerical simulation model were verified via field explosion tests. Furthermore, a theoretical correction model for the measured surface reflection pressure with respect to the installation angle was established, and a model calculation accuracy of 91.33%.

A 4-Channel High-Precision Real-Time Pressure Test System for Irregularly Variable High Temperature Environments

Abstract: In this study, a 4-channel high-precision pressure test system was designed. It implements high-precision measurement of pressure parameters at multiple test points in situ and synchronously in irregularly variable high-temperature environments. The test system consists of a pressure–temperature double-parameter composite sensor along with signal acquisition, temperature compensation algorithm processing, and real-time online display modules. The temperature-sensitive chip of the sensor was integrated on the surface of the differential pressure-sensitive chip for in-situ temperature compensation. The collected pressure-temperature parameters were calculated and displayed using the temperature compensation algorithm processing and real-time online display modules. Finally, a high-precision pressure test was conducted. The proposed test system realizes the pressure test in high-temperature environments with irregular variations in the range of 24–400 °C, with a test error of less than 0.95% and a sensitivity of 6.378 mV/kPa. The study results can be used for real-time monitoring of high-precision pressure of key components operating in irregularly variable high-temperature environments, which provides a significant guarantee for the normal operation of equipment.