Absolute Pressure Measurements Research Articles

State Primary Standard for the Pressure Unit in the Field of Absolute Pressure in the Range 1 · 10–1 – 7 · 105 Pa GET 101–2011: Analysis of the State and Development Trends

Issues related to the developmet and improvement of the metrological support system of the Russian Federation in the field of absolute pressure are considered; the main stages and results of theoretical and practical research work in the field of absolute pressure measurements carried out at the D. I. Mendeleyev Institute for Metrology are outlined. Historical information on the creation of primary standards and verification schedules in the field of pressure measurement is presented. A brief analysis of the state and development trends of world metrology in the field of absolute pressure measurement is carried out based on literature data and the results of key comparisons. The reasons for improving the State Primary Standard of the pressure unit in the field of absolute pressure are outlined, and ways to modernize the standard are proposed.The operating principles and design features of reference complexes from the State Primary Standard for the pressure unit in the field of absolute pressure GET 101–2011 are described. The main metrological characteristics of the standard are listed; the results of key comparisons, benchmark studies and international cooperation are published. The existing problems of the reference base of the Russian Federation in the field of absolute pressure and ways to improve the primary standard are outlined and analyzed. The metrological characteristics of the State Primary Standard for the pressure unit in the field of absolute pressure after completion of the modernization are assessed.

A new instrumentation for simultaneous terahertz and mid-infrared spectroscopy in corrosive gaseous mixtures.

The correct interpretation of infrared (IR) observations of planetary atmospheres requires an accurate knowledge of temperature and partial and global pressures. Precise laboratory measurements of absorption intensities and line profiles, in the 200-350K temperature range, are, therefore, critical. However, for gases only existing in complex chemical equilibria, such as nitrous or hypobromous acids, it is not possible to rely on absolute pressure measurements to measure absolute integrated optical absorption cross sections or IR line intensities. To overcome this difficulty, a novel dual-beam terahertz (THz)/mid-IR experimental setup has been developed, relying on the simultaneous use of two instruments. The setup involves a newly constructed temperature-controlled (200-350K) cross-shaped absorption cell made of inert materials. The cell is traversed by the mid-IR beam from a high-resolution Fourier transform spectrometer using along a White-cell optical configuration providing absorption path lengths from 2.8 to 42m and by a THz radiation beam (82.5GHz to 1.1THz), probing simultaneously the same gaseous sample. The THz channel records pure rotational lines of molecules for which the dipole moment was previously measured with high precision using Stark spectroscopy. This allows for a determination of the partial pressure in the gaseous mixture and enables absolute line intensities to be retrieved for the mid-IR range. This new instrument opens a new possibility for the retrieval of spectroscopic parameters for unstable molecules of atmospheric interest. The design and performance of the equipment are presented and illustrated by an example of simultaneous THz and mid-IR measurement on nitrous acid (HONO) equilibrium.

Field Study on Impact of Mechanical Pressurization on Pressure Distribution in High-Rise Buildings

In high-rise buildings, the excessive pressure differences cause various problems, and architectural and mechanical measures are always applied. In this study, pressure measurements on a 67-story high-rise building were conducted to evaluate the effect of mechanical pressurization on the pressure distribution. Absolute pressure measurement devices were installed at 28 points on 10 floors, a full-scale pressure profile of the test building was derived, and the pressure distributions on the main floors were reviewed. Four pressurization modes for the test building were considered, and the variation in the pressure distribution for each mode was analyzed. The results showed that mechanical pressurization reduced the pressure difference on the lobby floor by approximately 18%. Although it did not exert an apparent impact on the pressure difference due to the stack effect, pressurizing the entire floor serves as the most effective way of reducing the excessive pressure difference.

Calibrated Absolute Seafloor Pressure Measurements for Geodesy in Cascadia

AbstractThe boundary between the overriding and subducting plates is locked along some portions of the Cascadia subduction zone. The extent and location of locking affects the potential size and frequency of great earthquakes in the region. Because much of the boundary is offshore, measurements on land are incapable of completely defining a locked zone in the up‐dip region. Deformation models indicate that a record of seafloor height changes on the accretionary prism can reveal the extent of locking. To detect such changes, we have initiated a series of calibrated pressure measurements using an absolute self‐calibrating pressure recorder. A piston‐gauge calibrator under careful metrological considerations produces an absolutely known reference pressure to correct seafloor pressure observations to an absolute value. We report an accuracy of about 25 ppm of the water depth, or 0.02 kPa (0.2 cm equivalent) at 100 m to 0.8 kPa (8 cm equivalent) at 3,000 m. These campaign survey‐style absolute pressure measurements on seven offshore benchmarks in a line extending 100 km westward from Newport, Oregon from 2014 to 2017 establish a long‐term, sensor‐independent time series that can, over decades, reveal the extent of vertical deformation and thus the extent of plate locking and place initial limits on rates of subsidence or uplift. Continued surveys spanning years could serve as calibration values for co‐located or nearby continuous pressure records and provide useful information on possible crustal deformation rates, while epoch measurements spanning decades would provide further limits and additional insights on deformation.

A Novel Multisensor Device for Absolute Intracardiac Pressure Measurement, Detection, and Management of Heart Failure

A Novel Multisensor Device for Absolute Intracardiac Pressure Measurement, Detection, and Management of Heart Failure

Characterization of the Kinetyx SI Wireless Pressure-Measuring Insole during Benchtop Testing and Running Gait.

This study characterized the absolute pressure measurement error and reliability of a new fully integrated (Kinetyx, SI) plantar-pressure measurement system (PPMS) versus an industry-standard PPMS (F-Scan, Tekscan) during an established benchtop testing protocol as well as via a research-grade, instrumented treadmill (Bertec) during a running protocol. Benchtop testing results showed that both SI and F-Scan had strong positive linearity (Pearson's correlation coefficient, PCC = 0.86-0.97, PCC = 0.87-0.92; RMSE = 15.96 ± 9.49) and mean root mean squared error RMSE (9.17 ± 2.02) compared to the F-Scan on a progressive loading step test. The SI and F-Scan had comparable results for linearity and hysteresis on a sinusoidal loading test (PCC = 0.92-0.99; 5.04 ± 1.41; PCC = 0.94-0.99; 6.15 ± 1.39, respectively). SI had less mean RMSE (6.19 ± 1.38) than the F-Scan (8.66 ±2.31) on the sinusoidal test and less absolute error (4.08 ± 3.26) than the F-Scan (16.38 ± 12.43) on a static test. Both the SI and F-Scan had near-perfect between-day reliability interclass correlation coefficient, ICC = 0.97-1.00) to the F-Scan (ICC = 0.96-1.00). During running, the SI pressure output had a near-perfect linearity and low RMSE compared to the force measurement from the Bertec treadmill. However, the SI pressure output had a mean hysteresis of 7.67% with a 28.47% maximum hysteresis, which may have implications for the accurate quantification of kinetic gait measures during running.

Embedded Electronic Sensor for Monitoring of Breathing Activity, Fitting and Filter Clogging in Reusable Industrial Respirators.

Millions of workers are required to wear reusable respirators in several industries worldwide. Reusable respirators include filters that protect workers against harmful dust, smoke, gases, and vapors. These hazards may cause cancer, lung impairment, and diseases. Respiratory protection is prone to failure or misuse, such as wearing respirators with filters out of service life and employees wearing respirators loosely. Currently, there are no commercial systems capable of reliably alerting of misuse of respiratory protective equipment during the workday shifts or provide early information about dangerous clogging levels of filters. This paper proposes a low energy and non-obtrusive functional building block with embedded electronics that enable breathing monitoring inside an industrial reusable respirator. The embedded electronic device collects multidimensional data from an integrated pressure, temperature, and relative humidity sensor inside a reusable industrial respirator in real time and sends it wirelessly to an external platform for further processing. Here, the calculation of instantaneous breathing rate and estimation of the filter's respirator fitting and clogging level is performed. The device was tested with ten healthy subjects in laboratory trials. The subjects were asked to wear industrial reusable respirator with the embedded electronic device attached inside. The signals measured with the system were compared with airflow signals measured with calibrated transducers for validation purposes. The correlation between the estimated breathing rates using pressure, temperature, and relative humidity with the reference signal (airflow) is 0.987, 0.988 and 0.989 respectively, showing that instantaneous breathing rate can be calculated accurately using the information from the embedded device. Moreover, respirator fitting (well-fitted or loose condition) and filter's clogging levels (≤60%, 80% and 100% clogging) also can be estimated using features extracted from absolute pressure measurements combined to statistical analysis ANOVA models. These experimental outputs represent promising results for further development of data-driven prediction models using machine learning techniques to determine filters end-of-service life. Furthermore, the proposed system would collect relevant data for real-time monitoring of workers' breathing conditions and respirator usage, helping to improve occupational safety and health in the workplace.

Electrical resistance tomography-based multi-modality sensor and drift flux model for measurement of oil–gas–water flow

This paper proposes a novel method to measure each constituent of an oil–gas–water mixture in a water continuous flow, typically encountered in many processes. It deploys a dual-plane electrical resistance tomography sensor for measuring dispersed phase volume fraction and velocity; a gradiomanometer flow density meter and a drift flux model to estimate slip velocities; with absolute pressure and temperature measurements. These data are fused to estimate constituent volume flow rates. Other commonly used operational parameters can be further derived: water cut or water liquid ratio (WLR) and gas volume fraction (GVF). Trials are described for flow rates of water 5–10 m3 h−1; oil 2–10 m3 h−1 and gas 1–15 m3 h−1. The comparative results are included with published data from the Schlumberger Gould Research flow facility. The paper proposes the use of the described configuration for measurement of volume flow rates in oil–gas–water flows with an absolute error of ±10% within GVF 9%–85% and WLR > 45%.

Blood pressure adjustments throughout healthy and hypertensive pregnancy: A systematic review and meta-analysis.

Gestational hypertensive complications are preceded by deviant hemodynamic adjustments affecting blood pressure. Our objective was to determine the timing and magnitude of changes in blood pressure during singleton normotensive and hypertensive pregnancies. PubMed (NCBI) and Embase (Ovid) databases were searched for relevant studies up to November 2019. Studies reporting original blood pressure measurements during pregnancy together with a non-pregnant reference measurement were included. Studies including women with a history of cardiovascular or metabolic disease, or women using antihypertensive drugs were excluded. Pooled mean differences between pregnant and non-pregnant women, and absolute blood pressure values were calculated for predefined gestational intervals in normotensive and hypertensive pregnancy, using a random-effects model. Meta-regression analysis was used to analyze group differences in adjustments. In early normotensive pregnancy, both systolic and diastolic blood pressure decreased, reaching their maximum reduction of -4 mmHg (95%CI -6 to -1 mmHg) and -4 mmHg (95%CI, -5 to -3 mmHg), respectively in the second trimester. Thereafter, blood pressure gradually increased towards non-pregnant values. All absolute blood pressure measurements throughout normotensive pregnancy were below 130/80mmHg. In hypertensive pregnancies, only diastolic blood pressure decreased early in pregnancy. In conclusion, this meta-analysis showed a clinically moderate, but significant mid-pregnancy drop in blood pressure during normotensive pregnancy. Reference curves with absolute values underscore the current liberal cut-off limit for gestational hypertension. A lack of a mid-pregnancy systolic blood pressure drop might reflect increased vascular resistance in women destined to develop hypertensive pregnancy complications.

Pneumatic system for pressure probe measurements in transient flows of non-ideal vapors subject to line condensation

This paper presents the design, construction and commissioning of a pneumatic system for pressure probe measurements in flows of organic vapors in non-ideal conditions, namely in the thermodynamic region close to the liquid–vapor saturation curve and the critical point where the ideal gas law is not applicable.Experiments were carried out with fluid siloxane MM (hexamethyldisiloxane, C6H18OSi2), commonly employed in medium/high temperature Organic Rankine Cycles (ORCs), in the Test Rig for Organic VApors (TROVA), a blow-down wind tunnel at the Laboratory of Compressible fluid dynamics for Renewable Energy Applications (CREA lab) of Politecnico di Milano. TROVA operation is intrinsically transient due to its batch nature, with a low frequency content (∼1Hz) related to the emptying of the high-pressure reservoir feeding the test section.The challenges linked to possible condensation in pneumatic lines, such as vapor–liquid menisci, hydrostatic head and mass-sink effects, were evaluated by means of theoretical calculation and experiments. To avoid these issues, a nitrogen-flushed pneumatic system for absolute and differential pressure measurements was designed and successfully tested with superheated MM vapor expanding in planar choked converging nozzles characterized by a portion with constant cross-sectional area yielding design Mach numbers of 0.2, 0.5 and 0.7. Commissioning of the complete system including a probe was performed with the first ever testing of an L-shaped Pitot tube in non-ideal subsonic flows of siloxane MM vapor at Mach numbers M=0.2 and 0.5. Measurement delay issues were identified and assessed through a dynamic testing procedure, and were solved by reducing the overall pneumatic lines volume including the one hidden within pressure transducers. The correct performance of the complete system was therefore verified for probe measurements of total, static and dynamic pressure in non-ideal flows of organic vapors. This sets the foundation for future directional pressure probes calibration and use in the characterization of such flows, as in direct measurement of total pressure losses across shocks and in testing of ORC turbine blade cascades.

Optical phase contrast imaging for absolute, quantitative measurements of ultrasonic fields with frequencies up to 20 MHz.

The technique of phase contrast imaging, combined with tomographic reconstructions, can rapidly measure ultrasonic fields propagating in water, including ultrasonic fields with complex wavefront shapes, which are difficult to characterize with standard hydrophone measurements. Furthermore, the technique can measure the absolute pressure amplitudes of ultrasonic fields without requiring a pressure calibration. Absolute pressure measurements have been previously demonstrated using optical imaging methods for ultrasonic frequencies below 2.5 MHz. The present work demonstrates that phase contrast imaging can accurately measure ultrasonic fields with frequencies up to 20 MHz and pressure amplitudes near 10 kPa. Accurate measurements at high ultrasonic frequencies are performed by tailoring the measurement conditions to limit optical diffraction as guided by a simple dimensionless parameter. In some situations, differences between high frequency measurements made with the phase contrast method and a calibrated hydrophone become apparent, and the reasons for these differences are discussed. Extending optical imaging measurements to high ultrasonic frequencies could facilitate quantitative applications of ultrasound measurements in nondestructive testing and medical therapeutics and diagnostics such as photoacoustic imaging.

DAid pressure socks system: Performance evaluation

BackgroundPlantar pressure measurement has been proven to produce crucial information for gait analysis. Socks with integrated textile pressure sensors are a promising tool for non-obtrusive plantar pressure acquisition and monitoring. Research questionCan the DAid Pressure Socks System be employed for the measurement of plantar pressure and temporal parameters during walking? MethodPlantar pressure measurement was acquired simultaneously by the DAid Pressure Socks System (DPSS) and Pedar® insole measurement system for a normal walking gait of 17 volunteers. The measurement from both systems was processed and gait temporal parameters were calculated. The calculated temporal parameters included stride time, step time, stance time, swing time, single support time, double support time, and cadence. The Intraclass Correlation Coefficient (ICC) was calculated to evaluate the agreement between the plantar pressure measurement and temporal parameters obtained from both systems. ResultsFor plantar pressure measurement, excellent agreement (ICC > 0.90) was achieved in approximately 23 % cases, while in roughly 37 %, 27 %, and 13 % cases the agreement was good (ICC > 0.75), moderate (ICC > 0.50), and poor (ICC < 0.50), respectively. The mean relative differences (as a percentage) between the temporal parameter values calculated from the measurement of both systems were 0.80 % (stride time), 3.06 % (step time), 3.15 % (stance time), 5.08 % (swing time / opposite single support time), 14.47 % (double support time), and 0.78 % (cadence). SignificanceThe ICC result calculated for the plantar pressure measurement indicated a reasonable agreement between both systems. Additionally, the relatively low mean difference was observed for 5 out of 6 calculated temporal gait parameters. Consequently, the presented DPSS could be considered as a substitute for the commercial gait analysis tools for applications that do not require great accuracy of the absolute plantar pressure measurement.

Design and Fabrication of a MEMS Capacitance Vacuum Sensor Based on Silicon Buffer Block

An absolute MEMS capacitance vacuum sensor with a full range of (1-1000) Pa has been designed, fabricated and tested. The working principle of the capacitance vacuum sensor is explained and its fabrication process is introduced. For obtaining high sensitivity, the sensor's pressure-sensing diaphragm with large width-to-thickness ratio is manufactured using the silicon-on-insulator (SOI). A silicon buffer block is adopted to improve the linearity of the sensor and prevent the pressure-sensing diaphragm from being damaged due to overload. The sensor is packaged by anodic bonding process in a certain high vacuum environment to form a sealed cavity, in which the vacuum degree is maintained by the non-evaporable getter (NEG) film deposited on the buffer block surface. The absolute pressure measurement of the packaged sensor has been performed with a vacuum measurement system. The tests results show that the capacitance-pressure curve is piecewise linear in the full range (1-1000) Pa. And the sensor exhibits high stability and reproducibility. The maximum sensitivity of the sensor is 33.03 fF/Pa, while the resolution can reach 0.5 Pa. Moreover, the temperature characteristic of the sensor has been evaluated, and it turns out that the effect of temperature on the sensor is quite small in a certain temperature range.

Influence of pressure transducer protrusion depth on pressure measurements of shock waves in shock tubes.

This note investigates how small changes in the protrusion depth of a pressure transducer affect the pressure measurement of a moving shock wave. Measurements are undertaken with Kistler, Kulite, and PCB sensors in flush, recessed, and protruded sensor positions. Measurements of both absolute pressure and Mach number are shown to be insensitive to sensor protrusion depth. An assessment of sensor response time indicates a significantly shorter reaction time for the Kulite and PCB sensors compared with the Kistler sensor.

Membrane sandwich squeeze film pressure sensors

Squeeze film pressure sensors exploit the dynamical modification of the mechanical properties of oscillating elements due to the compression of a fluid in a small gap region and allow for direct and absolute pressure measurements. This Tutorial article discusses the working principles of membrane sandwich squeeze film pressure sensors—i.e., sensors comprised of a parallel arrangement of two large-area, ultrathin suspended films forming a few-micrometer gap, and immersed in a fluid—and focuses on their operation in the free molecular flow regime. The effects of gas pressure on the vibrations of the membrane resonators and their coupled dynamics are discussed in general terms before recent experimental implementations using high tensile stress silicon nitride membranes are presented.

Letter: Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage

Letter: Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage

Squeeze film pressure sensors based on SiN membrane sandwiches

We realize squeeze film pressure sensors using suspended, high mechanical quality silicon nitride membranes forming few-micron gap sandwiches. The effects of air pressure on the mechanical vibrations of the membranes are investigated in the range 10−3 − 50 mbar and the intermembrane coupling induced by the gas is discussed in light of a squeeze film coupled-oscillator model. The high responsivity (several kHz/mbar) and the sub-pascal sensitivity of such simple pressure sensors are attractive for absolute and direct pressure measurements in rarefied air or high vacuum environments.

A New Approach to Mechanical Loss Measurement of a Reciprocating Compressor

Changing energy regulations urge all appliance manufacturers to use more efficient components in their products. Reciprocating compressor is one of the most crucial part for the energy efficiency of a refrigerator. Not only electrical and thermodynamic but also mechanical efficiency is the crucial issue determining the coefficient of performance (COP) of a compressor. Therefore, precise and trustworthy measurement comprising the frictional losses is one of the critical parameters to anticipate the real effect of novel design concepts. The objective of this study is the development of a new approach to measure mechanical losses of a reciprocating compressor. The method is based on the precise measurement of deceleration. A test rig, where the oil temperature, ambient pressure and temperature are able to be adjusted, is established. Measurements are performed under different average load for varying oil viscosity level. Load conditions are provided by adjusting ambient pressure of the chamber in which compressor body is placed. A heater is used on the body of the compressor to simulate temperatures corresponding with real temperatures acquired from the measurements of the compressor. Compression work is calculated by measurement of absolute cylinder pressure with respect to angular position of the crank shaft. Results are promising to use this measurement system for more detailed investigation.

Experimental measurements of the high-temperature oxidation of carbon fibers

We carried out laboratory experiments to study the decomposition of carbon fibers at high temperature and studied the material used in charring carbon phenolic ablators for planetary probe heatshields. Porous plug samples were exposed to controlled rates of molecular oxygen, carbon dioxide, and carbon monoxide at furnace-heated flow-tube reactor temperatures between 700 and 1500 K and pressures between 2000 and 6200 Pa. We used calibrated mass spectroscopy to make time-resolved quantitative measurements of decomposition products of the gases downstream of the test sample. Absolute and differential pressure measurements were used to determine the high-temperature permeability of the material and to monitor changes during material decomposition, and we characterized the microstructure of the porous sample using scanning electron microscopy. We found substantial carbon fiber oxidation for O2 flows, resulting in increasing CO/CO2 production ratios with increasing temperature. The CO2 was shown to react with carbon fibers following a Boudouard reaction at temperatures above 1200 K.

Pengukuran Tekanan Absolut Biogas Berbahan Campuran Eceng Gondok Dan Kotoran Sapi

Biogas techniques is a way to produce energy with the anaerobic process by utilizing organic ingredients, one of which can be derived from herbs. The quality of biogas production can be viewed by performing the measurement of absolute pressure of biogas. Absolute pressure is the atmospheric pressure coupled with the measured pressure. The magnitude of the pressure will affect the quality of the flame produced biogas. This study, using the method of observation, and measurements. As for the data analysis techniques,. The findings focused to find the different of biogas production by measuring the change in absolute pressure of biogas. Measurements are done using a manometer. The results obtained show that the introduction by using cow dung retrieved changes pressure biogas occurred on day 3 with pressure 140.565 N/m2, the characteristics of the data graph illustrates the R2 = 0.677. Different results are indicated on the mixing water hyacinth with cow manure, biogas pressure changes happen on day 1 with the characteristic graph of a R2 = 0.976. This condition describes that the mixing of the water hyacinth and cow dung provides distinctions signifikant in accelerating the process of occurrence of biogas.