Absolute Pressure Sensor Research Articles

Designing a Bathymetric Sensor Using Absolute Pressure Sensors Arranged on a Regular Polyhedron

Designing a Bathymetric Sensor Using Absolute Pressure Sensors Arranged on a Regular Polyhedron

A new setup for measurements of absolute saturation vapor pressures using a dynamical method: Experimental concept and validation.

We describe a new experimental system for direct measurements of the absolute saturation vapor pressures of liquid or solid samples. The setup allows the isolation of the sample under steady conditions in an ultra-high vacuum chamber, where the measurement of the sample's vapor pressure as a function of its temperature can be performed in a range around room temperature and in a pressure range defined only by the applied absolute pressure sensor. We characterize the setup and illustrate its capability to measure saturation vapor pressures as well as enthalpies of evaporation around room temperature with explicit measurements on four liquid compounds (diethyl phthalate, 1-decanol, 1-heptanol, and 1-hexanol) for which accurate vapor pressures have previously been reported.

Squeeze film absolute pressure sensors with sub-millipascal sensitivity

We report on the realization of ultrasensitive absolute pressure sensors based on silicon nitride membrane sandwiches. These sandwiches consist in a pair of highly-pretensioned, ultrathin (50 nm), large area (0.25 mm2) films, suspended parallel to each other and forming an ultrashort (500 nm) open cavity. The compression of a gas in this cavity leads to a strong squeeze film force, resulting in an increase in the membrane mechanical resonance frequencies, which is directly proportional to the absolute gas pressure. These sandwiches show a record high responsivity of >300 Hz/Pa in terms of squeeze film-induced frequency shift in the range 10−3-100 Pa, which, combined with high quality factor mechanical resonances (Q>106), allows for bringing the sensitivity of absolute squeeze film pressure sensors down to the sub-millipascal level.

Design and demonstration of a sensing network for full-scale wind pressure measurements on buildings

There is a need for full-scale wind pressure measurements to evaluate the accuracy of peak wind load estimates from wind tunnel measurements, numerical simulations, or building codes. The objective of this study was to design a sensing network for obtaining long-term records of fluctuating wind pressures, and to demonstrate the network’s potential through deployment. A custom data-logger using the BMP388 absolute pressure sensor, which can measure pressure coefficients within ±0.1 at a wind speed of 10 m/s, was designed. The accuracy of the measured statistics was established through comparison with a standard differential sensor in a wind tunnel experiment. A network of 10 motes was deployed on the sloped roof of the 184 m tall Space Needle, obtaining over 1000 h of fluctuating pressure data. The measurements reveal a windward separation region with strong dependency of the approach wind turbulence on the pressure statistics, but positive skewness limits the peak values. The skewness becomes negative near the edge of a second, leeward separation region, resulting in peak factors up to 2.6 times larger than the code-prescribed value of 3.4. The results demonstrate that long-term full-scale measurements provide valuable insight into peak wind pressures and their dependence on approach wind characteristics.

A Comprehensive Review of MEMS-enabled Dual-mode Pressure and Temperature Sensors

This paper offers an examination of MEMS-enabled dual-mode sensors, emphasizing key concepts, technologies, and developments in the area. Micro-Electro-Mechanical Systems, or MEMS, have revolutionized sensor design, enabling the creation of small, effective, and multipurpose devices for simultaneous monitoring of temperature and pressure. The review begins with how MEMS and Integrated Circuits (ICs) are integrated into sensor systems and explores MEMS incorporation into dual-mode sensors, clarifying crucial manufacturing processes and design approaches. Furthermore, the paper classifies and examines basic MEMS sensor types, such as Surface Acoustic Wave (SAW), Barometers, Differential Pressure Sensors, Absolute Pressure Sensors, Strain Gauge Pressure Sensors, Accelerometer-Based Pressure Sensors, Magnetometer-Based Pressure Sensors, Fiber Bragg Grating (FBG) Temperature Sensors, and Force Sensors.

Field Observations of Hydrostatic Pressure Deviations in a Nearshore Sediment Bed

AbstractMomentary liquefaction (ML), an instantaneous loss of effective stress between individual sand grains, is caused by the upward vertical pressure gradient of the excess pore‐water pressure in the sediment during the passage of a wave. Few field experiments have provided detailed observations of vertical pressure gradients within a sediment bed. Here, a novel autonomous pressure‐profiling instrument, the Pressure Stick, was deployed in the surf zone of an ocean beach in Rye, New Hampshire. The Pressure Stick has eight time‐synced absolute pressure sensors distributed over a 70 cm distance to measure absolute pressure in the water column and in the sediment bed. The absence of direct measurements of the sediment‐water interface location and sediment porosity limit direct observations of ML but allow for an examination of the hydrostatic pressure deviations. Observed upward vertical pressure head gradients within the sediment exceed the assumed effective weight of the sediment. Exceedances of two ML thresholds are observed within 16 cm of the sediment‐water interface and consistently occur at the onset of steeper and larger wave crests. Individual waves are characterized with an approximation of the Sleath parameter and the depth normalized wave height. The ML thresholds are exceeded 1%–40% of the time when the Sleath parameter is greater than 0.1 and 1%–33% of the time when the depth normalized wave height is greater than 0.4. These results suggest that wave steepness and nonlinearity may be necessary to induce large vertical pressure gradients that substantially deviate from hydrostatic pressure.

Influence of gas density on void fraction and pressure drop in upward vapor–liquid flow

The influence of gas density on the void fraction, flow map, and pressure drop was examined for an upward vapor–liquid flow. The knowledge of the flow map is necessary to ensure a safe operational condition in a nuclear zone at high pressure. Moreover, the pressure gradient and its volumetric flow rate are related to the profitability of petroleum wells. Considering these scenarios, a modified cascade refrigeration cycle was constructed to generate and measure single-phase streams with different liquid and vapor density ratios. These single-phase liquid and vapor streams were mixed and injected into an upward vertical test section with an inner diameter of 26.64 mm and length of 5.8 m. The pressure ranged from 1.7 to 2.3 MPa, liquid–vapor density ratio ranged from 10.2 to 15.2, and total mass flux ranged from 733.1 to 882.9 kg.s−1.m−2. The void fraction, pressure gradient, and frictional pressure component were measured using quick-closing valves, temperature probes, and absolute and differential pressure sensors. The experimental data and transition line behavior of the flow map at high pressures in an upward two-phase flow as well as the proposed correction factors for the pressure gradient and its frictional component reflect the novelty of this study. Most existing studies have focused only on the influence of the gas density on the horizontal flow. A key observation of our study is that the liquid–vapor density ratio significantly changes the churn and annular transition lines. According to a vertical flow map found in the literature, the disappearance of the churn region can be foreseen and an annular transition occurs at lower gas velocities. The liquid–vapor density ratio does not influence the void fraction or slip velocity ratio; both increase with the superficial vapor velocity. Correction factors for the pressure gradient and its frictional component were proposed. The mean deviation for the pressure gradient was reduced from 27 % to 16 % after application of the correction factor. Half of the experimental points presented absolute relative errors lower than 30 % for the frictional pressure gradient. A cross-validation between the experimental data reported by other authors and the proposed correction factors was conducted to assess their response. In this cross-validation, 126 additional experimental points were used for the pressure gradient whereas 1270 points were used for its frictional component. Overall, the mean deviation of the pressure gradient was reduced from 92.7 % to 31.9 % after the application of the correction factor. Similarly, the mean deviation of the frictional gradient was reduced from 70.7 % to 31.3 % after the application of the correction factor. There was no evident influence of the liquid–vapor density ratio on the total pressure gradient and drift relationships for Froude numbers spanning from 2.6 to 7.4.

Fabrication of three-dimensional orthodontic force detecting brackets and preliminary clinical test for tooth movement simulation

This study aimed to develop an ultraminiature pressure sensor array to measure the force exerted on teeth. Orthodontic force plays an important role in effective, rapid, and safe tooth movement. However, owing to the lack of an adequate tool to measure the orthodontic force in vivo, it remains challenging to determine the best orthodontic loading in clinical and basic research. In this study, a three-dimensional (3D) orthodontic force detection system based on piezoresistive absolute pressure sensors was designed. The 3D force sensing array was constructed using five pressure sensors on a single chip. The size of the sensor array was only 4.1 × 2.6 mm, which can be placed within the bracket base area. Based on the barometric calibration, conversion formulas for the output voltage and pressure of the five channels were constructed. Subsequently, a 3D linear mechanical simulation model of the voltage and stress distribution was established using 312 tests of the applied force in 13 operating modes. Finally, the output voltage was first converted to pressure and then to the resultant force. The 3D force-detection chip was then tested to verify the accuracy of force measurement on the teeth. Based on the test results, the average output force error was only 0.0025 N (0.7169%) (p = 0.958), and the average spatial positioning error was only 0.058 mm (p = 0.872) on the X-axis and 0.050 mm (p = 0.837) on the Y-axis. The simulation results were highly consistent with the actual force applied (intraclass correlation efficient (ICC): 0.997–1.000; p < 0.001). Furthermore, through in vivo measurements and a finite element analysis, the movement trends generated when the measured orthodontic forces that acted on the teeth were simulated. The results revealed that the device can accurately measure the orthodontic force, representing the first clinical test of an orthodontic-force monitoring system. Our study provides a hardware basis for clinical research on efficient, safe, and optimal orthodontic forces, and has considerable potential for application in monitoring the biomechanics of tooth movement.

Flexible pressure/temperature sensors with heterogeneous integration of ultra-thin silicon and polymer

Flexible pressure sensors and temperature sensors are widely used in various fields because of their advantages in high flexibility, good shape retention and extremely small thickness. However, it is quite challenging to fabricate ultra-thin flexible pressure sensors with reliable sensing performance. In this work, we propose a new type of silicon–polymer heterogeneously integrated MEMS flexible sensor with an ultra-thin silicon-based absolute pressure sensing element and a thermistor. In the study, a flexible MEMS fabrication process is developed, which enables simultaneous fabrication in two different substrates and self-release of the thin and slim flexible sensor. The front-end section of the flexible sensor is with the width as 125 μm, length as 3.2 cm and total thickness as 12 μm, where the integrated silicon substrate thickness is only 3 μm. The sensor takes a slender shape to allow for medical invasive measurement by inserting it into a slim medical catheter or a syringe needle-tube. The sensitivity of the fabricated ultra-thin absolute pressure sensor is tested as 45.2 μV kPa−1 under 3.3 V supplied voltage, with the nonlinearity as only ±0.16% FS. The sensitivity of the thermistor is 10.4 Ω °C−1 in the range of 0 °C–100 °C. Moreover, the polysilicon thermistor can also serve as a micro-heater, where an electric heating power of 107 μW results in a temperature increase of 13.5 °C. With ultra-thin slim structure and satisfactory performance, the MEMS flexible sensor is promising in various fields like biomedical applications.

Silicon Micromachined TSVs for Backside Interconnection of Ultra-Small Pressure Sensors.

This paper presents an ultra-small absolute pressure sensor with a silicon-micromachined TSV backside interconnection for high-performance, high spatial resolution contact pressure sensing, including flexible-substrate applications. By exploiting silicon-micromachined TSVs that are compatibly fabricated with the pressure sensor, the sensing signals are emitted from the chip backside, thereby eliminating the fragile leads on the front-side. Such a design achieves a flat and fully passivated top surface to protect the sensor from mechanical damage, for reliable direct-contact pressure sensing. A single-crystal silicon beam-island structure is designed to reduce the deflection of the pressure-sensing diaphragm and improve output linearity. Using our group-developed microholes interetch and sealing (MIS) micromachining technique, we fabricated ultra-small piezoresistive pressure sensors with the chip size as small as 0.4 mm × 0.6 mm, in which the polysilicon-micromachined TSVs transfer the signal interconnection from the front-side to the backside of the wafer, and the sensor chips can be densely packaged on the flexible substrate via the TSVs. The ultra-small pressure sensor has high sensitivity of 0.84 mV/kPa under 3.3 V of supply voltage and low nonlinearity of ±0.09% full scale (FS) in the measurement range of 120 kPa. The proposed pressure sensors with backside-interconnection TSVs hold promise for tactile sensing applications, including flexible sensing of wearable wristwatches.

Impact of Supersonic Flow in Scintillator Detector Apertures on the Resulting Pumping Effect of the Vacuum Chambers

The article describes the combination of experimental measurements with mathematical–physics analyses in flow investigation in the chambers of the scintillator detector, which is a part of the environmental scanning electron microscope. The chambers are divided with apertures by small openings that keep the desirable pressure differences between three chambers: The specimen chamber, the differentially pumped intermediate chamber, and the scintillator chamber. There are conflicting demands on these apertures. On the one hand, the diameter of the apertures must be as big as possible so that they incur minimal losses of the passing secondary electrons. On the other hand, it is possible to magnify the apertures only to a certain extent so the rotary and turbomolecular vacuum pump can maintain the required operating pressures in separate chambers. The article describes the combination of experimental measurement using an absolute pressure sensor and mathematical physics analysis to map all the specifics of the emerging critical supersonic flow in apertures between the chambers. Based on the experiments and their tuned analyses, the most effective variant of combining the sizes of each aperture concerning different operating pressures in the detector is determined. The situation is made more difficult by the described fact that each aperture separates a different pressure gradient, so the gas flow through each aperture has its own characteristics with a different type of critical flow, and they influence each other, thereby influencing the final passage of secondary electrons detected by the scintillator and thus affecting the resulting displayed image.

A Single-Side Micromachined MPa-Scale High-Temperature Pressure Sensor.

This paper proposes a piezoresistive high-temperature absolute pressure sensor based on (100)/(111) hybrid SOI (silicon-on-insulator) silicon wafers, where the active layer is (100) silicon and the handle layer is (111) silicon. The 1.5 MPa ranged sensor chips are designed with the size as tiny as 0.5 × 0.5 mm, and the chips are fabricated only from the front side of the wafer for simple, high-yield and low-cost batch production. Herein, the (100) active layer is specifically used to form high-performance piezoresistors for high-temperature pressure sensing, while the (111) handle layer is used to single-side construct the pressure-sensing diaphragm and the pressure-reference cavity beneath the diaphragm. Benefitting from front-sided shallow dry etching and self-stop lateral wet etching inside the (111)-silicon substrate, the thickness of the pressure-sensing diaphragm is uniform and controllable, and the pressure-reference cavity is embedded into the handle layer of (111) silicon. Without the conventionally used double-sided etching, wafer bonding and cavity-SOI manufacturing, a very small sensor chip size of 0.5 × 0.5 mm is achieved. The measured performance of the 1.5 MPa ranged pressure sensor exhibits a full-scale output of approximately 59.55 mV/1500 kPa/3.3 VDC in room temperature and a high overall accuracy (combined with hysteresis, non-linearity and repeatability) of 0.17%FS within the temperature range of -55 °C to 350 °C. In addition, the thermal hysteresis is also evaluated as approximately 0.15%FS at 350 °C. The tiny-sized high temperature pressure sensors are promising in various industrial automatic control applications and wind tunnel testing systems.

Design and Analysis of High-Performance and Small-Size Piezoresistive Pressure Sensors

In this article, a rapid thermal process is proposed to manufacture piezoresistance to improve the performance of piezoresistive devices, and an absolute piezoresistive pressure sensor is prepared by anodic bonding between silicon film and glass with the cavity to reduce the size of the device. The size of the sensor is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0\times 1.0\times0.513$ </tex-math></inline-formula> mm. At the same time, the arrangement of piezoresistance is optimized by the finite element method. In addition, the deformation of the diaphragm is measured with a profiler, which verified the feasibility of Ti as the absorption of oxygen generated in the anodic bonding process. In the pressure range of 0–200 kPa, the output voltage and nonlinearity of the pressure sensor prepared by the rapid thermal annealing (RTP) process are 91.6 mV and 0.14%FSO, respectively, and the temperature coefficient of resistance (TCR) and the temperature coefficient of sensitivity (TCS) are 571 and −1676 ppm/°C respectively. Compared with the pressure sensor prepared by the common piezoresistive process, the TCR and TCS of the designed sensor are reduced by 73% and 24%, respectively, which has the advantages of high output voltage, low TCR and TCS, and small-size.

A High-Pressure Sensor With High Linearity With S-Shaped Piezoresistors

Silicon piezoresistive pressure sensors are widely used, and the pursuit of high linearity and high accuracy of sensors is always there. In this article, through simulations and calculations, including higher order piezoresistance effects, an S-shaped piezoresistor is proposed to optimize the linearity of pressure sensors; that is, the piezoresistive connecting arms are also lightly doped silicon. Two kinds of silicon piezoresistive absolute pressure sensors with a circular diaphragm in the range of 0–60 MPa were designed and fabricated, respectively, with tri-meander-shaped piezoresistors and S-shaped piezoresistors. After measurement, the linearity of the pressure sensor with S-shaped piezoresistors is about 30% better than that of the sensor with tri-meander-shaped piezoresistors, and the linearity and accuracy can reach 0.045% FS and 0.054% FS under the voltage source.

Identification of Soil Features Suitable for Barley, Maize and Sugarcane Cultivation using Precision Agriculture

Agriculture plays a crucial role in a nation's economy by significantly contributing to its Gross Domestic Product (GDP). Improved methods of farming not only benefit farmers by lowering their workload but also boost crop yields. Identifying the optimal soil for each crop is essential for producing harvests of the highest quality and quantity. Precision farming in agriculture uses Internet of Things (IoT) technology to ensure the most efficient use of available resources to increase crop yields and reduce operational costs. It reduces instances of crop failure and aids in averting catastrophic losses. Variations in soil temperature and soil moisture have the most significant influence on crop yield. The Soil Moisture Sensors calculate the soil's total volumetric water content. Using the BMP280 absolute barometric pressure sensor, it is possible to get accurate temperature and air pressure measurements. In the paper, the primary purpose of precision agriculture usage is to determine the optimal soil characteristics for the production of Barely, Maize and Sugarcane crops.

A package for piezoresistive pressure sensors with embedded built-in self-test function based on bimetallic actuator

Piezoresistive pressure sensors have been widely used in the industry and many other fields. However, conventional pressure sensor inspection is performed with the device off, which causes several inconveniences. In this article, an electrothermal actuator is designed and fabricated on the basis of bimetallic alloy material to realise the self-test of the piezoresistive silicon pressure sensor, and a kind of pressure sensor package structure with self-test capability is developed using the electrothermal actuator. Experimental results show that the structure can realise the dual excitation of the pressure and temperature of the diffused silicon pressure sensor core and enable it to return to the normal working state in less than 3.3 s. The self-test module can be driven at a low voltage of 0.8 V at less than 618 mW and can reflect the performance of the pressure sensor quickly and accurately. The structure is suitable for most differential pressure, absolute pressure sensor chips.

A Comparative Study of Design of Active Fault-Tolerant Control System for Air–Fuel Ratio Control of Internal Combustion Engine Using Particle Swarm Optimization, Genetic Algorithm, and Nonlinear Regression-Based Observer Model

In this article, three distinct strategies for designing an Active Fault-Tolerant Control System (AFTCS) for Air-Fuel Ratio (AFR) control of an Internal Combustion (IC) engine in a process plant to avoid engine shutdown, are presented. The proposed AFTCS employs a Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and a Nonlinear Regression (NLR)-based observer model in the Fault Detection and Isolation (FDI) unit for analytical redundancy. A comparison between these three proposed techniques is carried out to determine the least expensive and most accurate approach. The results show that the nonlinear regression produces highly accurate results by consuming very low computational power, and its response time is also very low as compared to GA and PSO. The results obtained show that NLR requires 99.6% and 93.1% less computational time for throttle and MAP estimation, respectively, by reducing the estimation error to as low as 0.01. The simulation of the proposed system is carried out in the MATLAB/Simulink environment. The results prove the superior fault tolerance performance for sensor faults of the AFR control system, especially for the Manifold Absolute Pressure (MAP) sensor in terms of less oscillatory response as compared to that reported in existing literature.

Theoretical Foundations of Construction of the Electronic System for Spatial Measuring of Air Signals Aircraft Plane’s with One Fixed Receiver of Incoming Air Flow

It is noted that it is necessary to obtain reliable information about air signals that determine the spatial movement of aircraft plane (AP), including small-sized, unmanned and manned, to ensure flight safety in the surface disturbed layer of the atmosphere. It is shown that traditional air data systems of AP implementing aerodynamic and wind cock methods for measuring the parameters of incoming air flow using air pressure receivers installed on the right and left side and distributed over the fuselage, braking temperature receiver and wind cock sensors of aerodynamic angles of incidence and gliding have a complex design, considerable weight and cost, which limits their use on small-sized, unmanned and other aircraft classes. It is noted that the developed air data system with one fixed receiver of incoming air flow, built on the basis of the vortex method for measuring the parameters of incoming air flow, can significantly simplify the design and reduce the mass of system, but provides measurement only in the azimuthal or vertical plane in a limited range of measurement of the aerodynamic angle. The air data system being developed, which implements an ion-mark method for measuring the parameters of incoming air flow, allows for panoramic measurement of the aerodynamic angle, but also only in one plane with increasing complexity of the design and increasing requirements for the identity of the channels of the multichannel measuring circuit, which also limits their use on small-sized aircraft. The known capabilities and advantages of the ultrasonic method for measuring the parameters of gas flows and a panoramic sensor of the aerodynamic angle and true airspeed with a fixed receiver of the incoming air flow have determined the possibility of using the ultrasonic method for spatial measurement of air signals. The functional scheme of the electronic system for spatial measuring air signals of aircraft plane with one (integrated) fixed receiver of incoming air flow and ultrasonic instrumentation channels connected to the input of the computer is revealed. To expand the functionality, a static pressure receiver-hole is installed on the external streamlined surface of the system’s receiving board, connected by a pneumatic channel to the input of an absolute pressure sensor with a frequency output, which is also connected to the input of a computer, at the output of which digital output signals of the air data system of aircraft plane are generated. Analytical models of informative signals and algorithms for spatial determination of air signals in instrumentation channels of the electronic system with one fixed receiver of incoming air flow are obtained. The essential advantages of the considered electronic system are revealed, which increase the competitiveness and efficiency of the system application on small-sized and other classes of aircraft planes to improve flight safety and the efficiency of solving flight tasks.

Monitoring of hydrogen-fueled engine backfires using dual manifold absolute pressure sensors

The application of hydrogen in internal combustion engines (ICE) has attracted widespread attention. However, due to the low ignition energy, high flame propagation speed, and wide combustible range of hydrogen, it is easy to cause abnormal combustion phenomena such as backfire in the port fuel injected (PFI) hydrogen-fueled engine. When a backfire occurs, the combustible mixture burns in the intake, resulting in a decrease in the volumetric efficiency of the engine, which may cause it to misfire or shut down in severe cases. Fast and accurate detection of backfire events is essential to take targeted control measures. In this research, a backfire detection system based on dual intake manifold absolute pressure (MAP) sensors were designed, with two MAP sensors installed on the intake manifolds of the first and fourth cylinders, and four gas injectors were installed on the intake manifold to convert the gasoline ICE into a hydrogen-fueled ICE. During the experiment, the engine speed was stabilized at 1000 rpm, the throttle valve was fully opened, and the intake pressure was maintained at 100 kPa.The test results show that the system can accurately determine the location and intensity of backfire occurrence. This method provides a basis for precise control of backfiring. • Set up two MAP sensors to monitor the backfiring of the hydrogen ICE. • MAP sensors allow accurate monitoring of backfiring. • Need to optimize valve strategy and injection strategy for hydrogen ICE.

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

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.