Dissertations / Theses on the topic 'Pressure sensor'

As far as the Printed Circuit Boards (PCB) manufacture industry is concerned, for high production volumes, solder paste is applied on the connection pads through customized stencils. This is a very productive method, yet if the design has to be updated, cost is increasing as the stencil should be changed. For higher exibility, such as in rapid prototyping, jet-printing machines similar to Mycronic MY500 are used. In these equipments, solder paste is jet-printed on the circuit board. The shooting is done by a piston moving on the vertical axis at high speed, hence projecting solder paste onto the connection pads of the PCB. In order to improve the understanding of the jetting process, it is important to collect data on pressure uctuations in the jetting head. To do so, this project is using a strain gauge to sense the strain applied by the piston on the nozzle. The gauge is connected in a Wheatstone bridge, and the differential signal is extracted and amplified a first time with an instrumentation amplifier. The remaining amplification is then performed with the help of an operational amplifier so that the signal matches the Analog to Digital Converter (ADC) levels. Finally, the converted results are transmitted to a personal computer for further analysis.

This thesis considers the design and implementation of passive wireless microwave readable pressure sensors on a single chip. Two novel-all passive devices are considered for wireless pressure operation. The first device consists of a tuned circuit operating at 10 GHz fabricated on SiO2 membrane, supported on a silicon wafer. A pressure difference across the membrane causes it to deflect so that a passive resonant circuit detunes. The circuit is remotely interrogated to read off the sensor data. The chip area is 20 mm2 and the membrane area is 2mm2 with thickness of 4 µm. Two on chip passive resonant circuits were investigated: a meandered dipole and a zigzag antenna. Both have a physical length of 4.25 mm. the sensors show a shift in their resonant frequency in response to changing pressure of 10.28-10.27 GHz for the meandered dipole, and 9.61-9.58 GHz for the zigzag antenna. The sensitivities of the meandered dipole and zigzag sensors are 12.5 kHz and 16 kHz mbar, respectively. The second device is a pressure sensor on CMOS chip. The sensing element is capacitor array covering an area of 2 mm2 on a membrane. This sensor is coupled with a dipole antenna operating at 8.77 GHz. The post processing of the CMOS chip is carried out only in three steps, and the sensor on its own shows a sensitivity of 0.47fF/mbar and wireless sensitivity of 27 kHz/mbar. The MIM capacitors on membrane can be used to detune the resonant frequency of an antenna.

Miniature pressure sensors which can endure harsh environments are a highly sought after goal in industrial, medical and research fields. Microelectromechanical systems (MEMS) are the current methods to fabricate such small sensors. However, they suffer from low sensitivity and poor mechanical properties.

To fulfill the need for robust and reliable miniature pressure sensors that can operate under high temperatures, a novel type of optical fiber tip sensor only 125μm in diameter is presented in this thesis. The essential element is a piece of hollow fiber which connects the fiber end and a diaphragm to form a Fabry-Pérot cavity. The all-fused-silica structure fabricated directly on a fiber tip has little temperature dependence and can function very well with high resolution and accuracy at temperatures up to 600ï °C. In addition to its miniature size, its advantages include superior mechanical properties, biocompatibility, immunity to electromagnetic interference, disposability and cost-effective fabrication.

The principle of operation, design analysis, fabrication implementation and performance evaluation of the sensor are discussed in detail in the following chapters.

Master of Science

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
Thesis presented in partial fulfilment of the requirements for the degree Master of Science in Engineering at the University of Stellenbosch
ENGLISH ABSTRACT: Measurement of pressure with zinc oxide (ZnO) nanowires was investigated. ZnO exhibits the piezoelectric effect, generating a voltage when pressure is applied to the material. This relationship between pressure and output voltage was used to make a pressure sensor. A study of the physical and mathematical working of the piezoelectric effect in ZnO nanowires was done. Simulations were conducted by means of specialised software to test the theory. The simulations gave results as the theory had predicted. ZnO nanowires were grown using various methods. Vapour liquid solid (VLS) was found to be the best method to grow uniform and dense arrays of ZnO nanowires. Statistical methods were employed to obtain the optimal parameters for the growth of ZnO nanowires through the VLS method. After the growth of the ZnO nanowires a pressure sensor was built. The manufacturing of the pressure sensor consisted of different steps. The sensors were tested to verify that they worked as described in theory and as shown in the simulations. The output voltage was lower than the simulated value due to imperfections and losses throughout the system. The output voltage versus applied pressure graphs did coincide with the bulk ZnO materials as well as related products, such as force sensing resistors. The output voltage is too low, but there are various methods by which the output voltage can be increased. These methods are discussed. The finished sensor can be used to continuously monitor pressure on a plane.
AFRIKAANSE OPSOMMING: Die meting van druk deur sink oksied (ZnO) nanodrade was ondersoek. ZnO toon die piëzo-elektriese effek - spanning word gegenereer wanneer druk op die materiaal aangewend word. Hierdie verhouding tussen druk en uitsetspanning is gebruik om ’n druksensor te vervaardig. ’n Studie van die fisiese en wiskundige werking van die piëzo-elektriese effek in ZnO nanodrade is gedoen. Simulasies deur middel van gespesialiseerde sagteware is uitgevoer om die teorie te bevestig. Die simulasies het resultate getoon soos deur die teorie beskryf word. ZnO nanodrade is gegroei deur verskillende metodes. Verdamping vloeistof vastestof (VVV) is as die beste metode gevind om uniforme en digte skikkings van ZnO nanodrade te kry. Statistiese metodes is aangewend om die optimale parameters vir die groei van ZnO nanodrade deur middel van die VVV metode te kry. Na afloop van die groei van die ZnO nanodrade is ’n druksensor vervaardig. Die vervaardigingsproses het uit verskillende stappe bestaan, ten einde die bou van ’n werkende druksensor uit die ZnO nanodrade te realiseer. Die sensors is getoets om te bevestig dat dit werk, soos beskryf deur die teorie en gewys in die simulasies. Die uitsetspanning was laer as wat verwag was as gevolg van onvolmaakthede en verliese in die hele stelsel. Die uitsetspanning teenoor druk grafieke van die sensor het ooreengestem met die van die grootmaat materiale, asook verwante produkte soos druk sensitiewe weerstande. Die uitset spanning is baie laag en daar bestaan verskillende maniere waarop die uitsetspanning verhoog kan word. Hierdie metodes word bespreek.

Fabrication and characterization of a new kind of pressure sensor using self-assembly Zinc Oxide (ZnO) nanowires on top of the gate of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is presented. Self-assembly ZnO nanowires were fabricated with a diameter of 80 nm and 800 nm height (80:8 aspect ratio) on top of the gate of the MOSFET. The sensor showed a 110% response in the drain current due to pressure, even with the expected piezoresistive response of the silicon device removed from the measurement. The pressure sensor was fabricated through low temperature bottom up ultrahigh aspect ratio ZnO nanowire growth using anodic alumina oxide (AAO) templates. The pressure sensor has two main components: MOSFET and ZnO nanowires. Silicon Dioxide growth, photolithography, dopant diffusion, and aluminum metallization were used to fabricate a basic MOSFET. In the other hand, a combination of aluminum anodization, alumina barrier layer removal, ZnO atomic layer deposition (ALD), and wet etching for nanowire release were optimized to fabricate the sensor on a silicon wafer. The ZnO nanowire fabrication sequence presented is at low temperature making it compatible with CMOS technology.

This thesis describes utilization of a nanotechnology in new pressure sensors. Detailed analysis of individual principles are carrying on. And simulations and experimental models of sensors are developed. More detailed description is provided for new capacitive pressure sensor, which is manufactured using nanotechnology, including its model and analysis in order to improve its properties. The work deals with the emission pressure sensor which uses the principle of cold emissions, including analysis comparison of the measured values of the emission current from the applied nanotubes field and analysis to improve emissions performance.

Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace. It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough. The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly. The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC.
Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen. Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter. Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen. Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.
Includes bibliographical references (leaves 101-105).
by Lalitha Parameswaran.
M.S.

Silicon based micromachining technology enables the realization of high performance micro electromechanical systems (MEMS) including a range of physical and environmental sensors. Pressure sensors are used for a wide range of monitoring and control applications, e.g. environmental, industrial, aircraft, automotive. Monitoring of vehicle tyre pressures offers benefits such as improved safety, fuel economy, and tyre life. Micromachined pressure sensors are used at present, but require further research to improve their performance in terms of size, power consumption and manufacturing cost. This thesis has reviews pressure sensor technology and new developments in this area. A comparison of existing and potential future sensing mechanisms has been undertaken and identified as silicon piezoresistors. The focus of the research is motivated by the recently discovered enhanced piezoresistive effect in silicon nanowires where sensitivity can be increased by decreasing the dimension of nanowire. This thesis investigates the piezoresistive effect in p-type <110> silicon nanowires, fabricated using top down approach. It is found that the piezoresistive effect increases when the nanowire width is reduced below 400nm. Compared with micrometre sized piezoresistors, silicon nanowires have produced up to 100% enhancement. In addition, measurements indicate that the temperature coefficient of resistance (TCR) of silicon nanowire has improved with up to 40% decrease in TCR. The improvement in these two areas will be beneficial for the development of new MEMS pressure sensors. COMSOL is employed to simulate the piezoresistance effect in p-type <110> silicon for a range of doping concentrations. Simulation results demonstrate a similar trend to experimental results and publication data and show that the piezoresistance effect decreases as the doping concentration increases.

Wearable wireless sensor devices, which are implemented by deploying sensor nodes on objects, are widely utilized in a broad field of applica-tions, especially in the healthcare system for improving the quality of life or monitoring different types of physical data from the observed objects. The aim of this study is to design an in-home, small-size and long-term wearable fall detection system in wireless network by using barometric pressure sensing for elderly or patient who needs healthcare monitoring. This threshold-based fall detection system is to measure the altitude of different positions on the human body, and detect the fall event from that altitude information. As a surveillance system, it would trigger an alert when the fall event occurs so that to protect people from the potential life risk by immediate rescue and treatment. After all the performances evaluation, the measurement result shows that standing, sitting and fall state was detected with 100% accuracy and lying on bed state was detected with 93.3% accuracy by using this wireless fall detection system. Furthermore, this system with low power consumption on battery-node can operate continuously up to 150 days.

This research focuses on developing sensors for properties of aerodynamic interest (i.e., flow and pressure) based on low-cost polymeric materials and simple fabrication processes. Such sensors can be fabricated in large arrays, covering the surface of airfoils typically used in unmanned vehicles, allowing for the detection of flow separation. This in turn potentially enables, through the use of closed-loop control, an expansion of the flight envelope of these vehicles. A key advance is compensation for the typically inferior performance of these low cost materials through both careful design as well as new readout methods that reduce drift, namely a readout methodology based on aeroelastic flutter. An all-polymer micromachined piezoresistive flow sensor is fabricated, based on a flexible polyimide substrate and an elastomeric piezoresistive composite material. The flow sensor comprises a cantilever that is extended into the embedding flow; flow-induced stress on the cantilever is sensed through the piezoresistive composite material. Increasing the sensitivity of the sensor is achieved by either utilizing a long single-cantilever beam or using a dual-cantilever beam supporting a flap extending into the flow. In the latter case, the sensor demonstrates increased sensitivity with a reduced cantilever length. The increase in sensitivity helps to reduce sensor drift, which in turn is further reduced by a new measurement method, the vibration amplitude measurement method. In this drift reduction measurement method, the flow-induced vibration amplitude of the sensor structure (i.e., the amplitude of the aeroelastic flutter induced by the flow), instead of the absolute value of cantilever deflection, is measured in order to find the flow rate. Measurement of this relative resistance change instead of the absolute resistance in the piezoresistor rejects common-mode drift and greatly reduces overall drift. Experimental results verify the expected drift reduction. Sensor drift is also reduced when the elastomeric piezoresistive material is replaced by a Pt thin film piezoresistor. Development of pressure sensors based on polymers proceeds by encapsulating a reference cavity within a multilayer polymer structure and forming capacitor plates on the polymeric membranes encapsulating the cavity. Measuring the capacitance change induced by changes in the embedding pressure (which cause changes in the positions of the bounding polymeric membranes) enables calculation of the pressure. The use of polymeric membranes requires understanding the leakage rate of gas into the reference cavity, which is a source of pressure drift. Developing a polymer-based pressure sensor that solves the problem of sensor drift as a result of gas permeation entails the fabrication of a silicon pressure reference cavity embedded in the polymer substrate, which results in a more hermetic and lower drift sensor while preserving the flexibility of the embedding polymer. Both wired and wireless versions of pressure and flow sensors of these types were developed and characterized. Further, the sensors were characterized on airfoils and their performance in a wind tunnel was determined.

A technology for fabricating fiber optic pressure sensors is described. This technology is based on intermediate-layer bonding of a fused silica ferrule to a patterned, micro-machined fused silica diaphragm, providing low temperature fabrication of optical pressure sensor heads that can operate at high temperature. Fused silica ferrules and fused silica diaphragms are chosen to reduce the temperature dependence. The fused silica diaphragms have been micro-machined using wet chemical etching in order to form extrinsic Fabry-Perot (FP) interferometric cavities. Sol-gel is used as an intermediate-layer for both fiber-ferrule bonding and ferrule-diaphragm bonding at relatively low temperature (250 °C). The pressure sensors fabricated in the manner can operate at temperatures as high as 600 °C. The self-calibrated interferometric-intensity-based (SCIIB) technology, which combines fiber interferometry and intensity-based sensing method into a single sensor system, is used to test and monitor the pressure sensor signal. The light returned from the FP cavity is split into two channels. One channel with longer coherence length can test the effective interference generated by the FP cavity, while the other channel with shorter coherence length can get signal proportional only to the source power, fiber attenuation, and other optical losses. The ratio of the signals from the two channels can compensate for all unwanted factors, including source power variations and fiber bending losses. [11]
Master of Science

To fulfill the objective of providing robust and reliable fiber optic pressure sensors capable of operating in harsh environments, this dissertation presents the detailed research work on the design, modeling, implementation, analysis, and performance evaluation of the novel fiber optic self-calibrated interferometric/intensity-based (SCIIB) pressure sensor system. By self-referencing its two channels outputs, for the first time to our knowledge, the developed SCIIB technology can fully compensate for the fluctuation of source power and the variations of fiber losses. Based on the SCIIB principle, both multimode and single-mode fiber-based SCIIB sensor systems were designed and successfully implemented. To achieve all the potential advantages of the SCIIB technology, the novel controlled thermal bonding method was proposed, designed, and developed to fabricate high performance fiber optic Fabry-Perot sensor probes with excellent mechanical strength and temperature stability. Mathematical models of the sensor in response to the pressure and temperature are studied to provide a guideline for optimal design of the sensor probe. The solid and detailed noise analysis is also presented to provide a better understanding of the performance limitation of the SCIIB system. Based on the system noise analysis results, optimization measures are proposed to improve the system performance. Extensive experiments have also been conducted to systematically evaluate the performance of the instrumentation systems and the sensor probes. The major test results give us the confidence to believe that the development of the fiber optic SCIIB pressure sensor system provides a reliable pressure measurement tool capable of operating in high pressure, high temperature harsh environments.
Ph. D.

With the prolonged lifespan of the average person, the number of hospital stays have increased. Currently, pressure ulcers are one of the most severe complications associated with prolonged hospital stay. The protocol in today€™s hospital is to rotate bedridden patients once every two hours to prevent pressure ulcers. This puts a strain on attending nurses as the risk of a pressure ulcer for a patient is not universal and therefore, a universal preventative protocol is not the most effective solution. This thesis describes the circuit design and physical implementation of a device to address the issue of pressure ulcers. The device has the form factor of a patch to be placed on specific, at risk areas of the human body. The device was designed and prototyped first on a rigid structure and then on a flexible printed circuit board substrate. A calibration procedure was developed to reduce part to part variability inherent to the pressure sensor. The resistance measurement was achieved through a novel approach including the use of a timer removing the need for an analog-to-digital converter. A seven hour experiment was conducted with live, animal subjects to measure the pressure and temperature of at risk areas of the body. The results of the experiment successfully prove the fundamental approach outlined in this thesis and justify continued research and refinement into the product design.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Boeing Commercial Airplanes has used many methods in the past to measure the structural loads on the wings of its airplanes. The most recent approach is to use arrays of MEMS pressure sensors on the top and bottom surfaces of the wings. By knowing the difference in pressure between the top and bottom of the wings the structural loads on the wings can be calculated. It was decided that in order to build an array of 1100 sensors it would be necessary to condition the sensors and convert the analog output to a digital form at the site of the pressure measurement. This process was taken one step further by converting the output of the A/D converter into engineering units within the sensor module as well. The array is built using a flex circuit card in one foot sections that can be interconnected to form an array of up to 125 sensors. There is a sensor location every two inches on the flex circuit but not all locations are populated. This paper will describe not only the pressure belt but the lessons learned during the development and the implications that these lessons have for smart transducers in general.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Systems Science and Industrial Engineering Department, 2006.
Includes bibliographical references.

Due to a globally aging population, there is a growing demand for smart home technology which can serve to monitor the health and safety of adults. Therefore, sleep monitoring has emerged as a crucial tool to improve the health and autonomy of adults. While polysomnography (PSG) is an effective and accurate tool for sleep monitoring, it is obtrusive as the user must wear the instruments during the experiment. Therefore, there has been a growing interest in deploying unobtrusive sleep monitoring devices, specifically for long-term patient monitoring. This thesis proposes multiple algorithms applicable to unobtrusive pressure sensitive sensor arrays in order to assess sleep quality. These algorithms can be listed as adaptive movement detection, sensor data fusion and bed occupancy detection. This thesis also investigates long-term sleep pattern changes from previously recorded data. The methods developed in the thesis can be of interest for future clinical remote patient monitoring systems.

This thesis is concerned with the design and building of a foot pressure system capable of measuring the pressure distribution underneath the diabetic foot. The system is developed to have a higher resolution and be more cost-effective than existing commercial systems. The biomechanics of the foot and ankle is explained in detail, providing an explanation for the relationship between high pressures and ulcerations. Various techniques of measuring foot pressure are reviewed, providing a thorough understanding of the advantages and disadvantages of each technique. The system developed uses the technique of interferometry, which is discussed in detail, explaining why the Fizeau Interferometer technique was chosen over other interferometer techniques. A number of materials were tested as to their suitability to be used as the pressure plate in the system i.e. compression/force relationship. From the results 'Perspex' was found to be the most suitable material. Two fringe-processing software packages were tested i.e. Fringe Processor 2 and Fringe Pattern Analysis (FRAN), with Fringe Processor 2 being chosen for this research. A graphical user interface for image display was created in order to display and analyse the various pressure images. Three prototypes were implemented. The first used a variation on the Fizeau interferometer, the second used a variation on the Twyman Green interferometer, whilst the third improved on the use of the variation of the Fizeau interferometer. By analysing the advantages and disadvantages of each prototype, the 3 rd prototype was chosen as the most suitable for achieving the aims and objectives of this research. This prototype was subjected to various tests i.e. resolution, measurable area, repeatability, calibration, short term reliability and sensitivity to heat. Various normal and pathological foot measurements were taken and analysed, and the effectiveness of the image display graphical user interface tested. The main contribution of this thesis is the use of interferometry to measure pressure. This in turn provides a foot pressure system, which has extremely high resolution and accuracy. The simple nature of the new pressure system also means that the entire system is very cost effective.

As a nation that depends so heavily on its infrastructure, the United Statescontinually seeks to better maintain the investment that it has made in its roadways.Asphalt pavements make up the majority of the paved roadways in the United States andultimately contribute to the bulk of the expense of highway maintenance. The goal ofthis research was to develop a means for taking a simple measurement of pressure atvarious interfaces on and within an asphalt pavement structure in an effort to directlyassess the damaging effects of different wheel loadings. It is well known that everincreasing wheel loads and other unusual wheel loading conditions are detrimental to theeffort of maintaining the roadways. The results of the data can be compared to the classicempiricalistic and mechanistic approaches to asphalt pavement design and analysis, aswell as the more modern finite-element computer modeling programs. The Tekscanmeasurement system, which utilizes a very thin matrix based pressure sensitive sensor,has been deemed applicable for measuring pavement pressures. Various types of wheelloadings have been considered throughout this study. It was determined that the type oftire, tire inflation pressure, applied load, and the asphalt itself all have an effect on theresultant pressures on the surface of and within an asphalt pavement structure. Thisresearch may contribute to the understanding of pressure distributions at the tire/asphaltinterface depending on the type of tire, adjustments in tire inflation pressure, and varyingthe wheel load. The results may lead to a better understanding of pressure distributions atvarying depths within an asphalt pavement structure. The ability to quantify thesevariables could assist designers when analyzing and designing asphalt pavements.

碩士
遠東技術學院
機械研究所
92
In this study use the half and double Wheatstone bridge circuit design methods to improve the defect of single Wheatstone bridge form micro pressure sensor dependent of temperature. According to the results, the error of voltage output is high to 21.2% when the temperature is from 30 0C to 100 0C. To go to such the error of voltage output of the half and double Wheatstone bridge form micro pressure sensor are down to 6.25% and 0.03%. Especailly, the voltage output of the double Wheatstone bridge form micro pressure sensor is almost independent of temperature. Beside, the linear operation pressure of the half and double Wheatstone bridge form micro pressure sensor up to 130 psi are 1.3 times for the single Wheatstone bridge form micro pressure sensor.

碩士
國立交通大學
電子研究所
83
Micro-electro-mechanical systems( MEMS ) is a large field of study, because it combines two major subjects, i.e., electronic and mechanical engineering. Fabricated by IC technologies, emp- loying diaphragm deformed by pressure to generate electrical si- gnal, pressure sensor is the most representative device in this topic. This thesis thus majors in the capacitive pressure sensor in order to get into the field of MEMS. Capacitive pressure sensor can be considered as the parallel plates capacitor. One of the plates is a very thin diaphragm, so it would be deformed as pressure varying and the capacitance wo- uld be changed. Therefore, we can obtain the pressure value by the altering value of the capacitance. Because the structure of the pressure sensor device differs from the traditional IC's devices, the ways of fabricating pressure sensor are also diff- erent from traditional IC's technologies, such as KOH etching, P+ diaphragm formation, anodic bonding technique etc. These all will be extensively discussed in this thesis. At last, we generally introduce the silicon sensors and some special fabricating processes or thinkings about micromachining field in order to understand this topic extensively.

碩士
國立交通大學
電子工程學系
85
Semiconuctor sensors are usually fabricated using processes that is developedfor integrated circuits;furthermore,many specialized fabrication steps includeanisotropic etching to form diaphragm, and the use of sacrificial layers toform free- standing beams or membranes is needed.Those processes are refered toas micromachining, according to the feature dimensions of the sensors are of the order of micros, and the spacing between sensor parts maybe one micro orless. The key point of this thesis focuses on the fabrication processes of the cap- acitive pressure sensor;consequently, a detailed study of processes will beshown,especially in KOH anisotropic etching,p+ layer formation,and anodic bonding process. On the other hand, we will also show the measurement and testingresults of this sensor respectively.

碩士
國立交通大學
電子研究所
84
Microelectromechanical systems (MEMS) is predicted to be the star offuture industry. By means of the IC technology, the mechanical properties ofsilicon can be applied to many fields in our life. Microsensors and microactuators are the typical applications in this field, among the otherthings. The key point of this thesis focuses on the fabrication processes of the three electrodes capacitive pressure sensor. A detailed study of processes will be showed, especially in cavity formation and p+ layer formation.Nevertheless, we also mention an introduction about the design considerations. Finally, to improve the study of capacitive pressure sensor, we give a sincerethinking in chapter four.

碩士
國立臺灣大學
應用力學研究所
84
Surface micromachined piezoresistive pressure sensor has been designed, modeled, and fabricated. The optimal position, orientation, and length of effective resistors on circular and square plate have been found. The sensitivity of 0.15 mV/V/psi could be achieved by the optimization design. The linearity error of pressure sensor is dominated by the large deflection of plates. The strain under large deflection of circular and square plates could be solved by the methods of S. P. Timoshenko and A. Foppl respectively. Experimental measurements showed consistent agreement. Because the solutions are analytic, they could be used in the linearity compensation circuitry. The output voltage of pressure sensor and temperature relationships have been predicted by Y. Kanda's theory and verified by experimental measurements. It could be used in the temperature compensation circuitry. We conquer some difficulties to fabricate surface micromachined piezoresistive pressure sensor in the Semi Conductor Research Center, NCTU. It shows the possibility of fabricating surface micromachined pressure sensor in Taiwan.

碩士
國立臺北科技大學
製造科技研究所
103
In previous studies, intradiscal pressure was used as an important reference data measure in spine biomechanics research. When a healthy intervertebral disc is under loading, the intradiscal pressure will be increased proportionally with loading. We can investigate the physiological mechanics of disc by measuring the intradiscal pressure. In previous studies, strain gage needle-type of pressure sensor was used as the mainstream method for the measurement of intradiscal pressure. The advantage of this sensor is its accuracy and inexpensive to fabricate, but the disadvantage is that its size is still too large to be used on the intervertebral disc. The strain gage needle-type pressure sensor may compromise the disc easily during insertion and lead to experimental errors. The purpose of this study is to develop a standardized procedure to produce three kinds of 18G needle-type pressure sensors. Then the three sensor types were assessed and the performance for each type of sensor was evaluated by a static test protocol, and the intradiscal pressure were measured using three different insertion methods. Finally, the best insertion method was found by evaluating the intradiscal pressure values and the sensitivity of different pressure sensor types. The current study was divided into four parts. 1. Needle-type pressure sensor fabrication: 18G of needle was fabricated to the desired shape by using wire electrical discharge machining (EDM) techniques, and the strain gage was adhered to the grooves of the needle by using a specially-designed device. Then the needle was encapsulated and underwent a waterproof test. 2. Static pressure calibration test: a static pressure calibration test was performed on the needle sensor according to the ASTM D5720 standard. The pressure range for the static test was obtained by using the max pressure value that a needle sensor passed the waterproof test. From the static test, the linear, hysteresis repeatability, and accuracy of the pressure sensor were calculated. 3. Intradiscal pressure measurement: pressure sensor was inserted using different methods to measure the intradiscal pressure. 4. Inspection of the pressure sensor and comparison of the intradiscal pressure measured: the pressure sensors were inspected again using the static pressure calibration test again following the measurement of intradiscal pressure. The best measurement method was found by evaluating the sensitivity of static pressure calibration test and the intradiscal pressure results. The results of waterproof test showed that the waterproof performance of the first sensor type was about 1.5MPa, while the other two sensor types were about 3MPa. The results from the static pressure calibration test showed that only the first sensor type with good sensitivity and the measurement error is less than 10% and the production time is the shortest as compared to other types of sensor. From the results of intradiscal pressure, the first and the third measurement methods are consistent with the measurement range of the past literature. The results of static pressure calibration test before and after the intradiscal pressure experiment showed that the third measurement method has less influence on for the pressure sensors and the accuracy of the pressure sensor is still good after the intradiscal pressure experiment and the variation of sensitivity is 1.5%.

碩士
國立屏東科技大學
車輛工程系碩士班
95
This study adopts Microelectroforming of magnetic alloy membrane, and matches with lithography fabrication process of high depth-width ratio, Micromachining Technology and Micro-magnetic Alloy Electroforming to apply on micro-pressure sensor. With the innovative Micro-magnetic Alloy Microelectroforming and low resistance of copper electroform coil, this study has designed a high accuracy and dynamic measurement of micro-pressure sensor. The manufacturing process of Microelectroforming of magnetic alloy membrane is to manufacture the FE/Ni magnetic alloy to high sensitive magnetic membrane by Magnetic Alloy Electroforming. Then it matches with Thick Film Photo-resist AZ-4620 and Micro-copper Electroforming, and high conductivity copper induction coil is designed. Finally, with the Bulk Micromachining Technology , the Buffered Oxide Etching (BOE) is used to etch suitable pressure cavity. Then the magnetic micro-pressure sensor can be obtained. The experimental result shows that the when the temperature of plating solution is 50℃, current density is 5ASD and period is one hour, the etched electric membrane is relatively stable. For the magnetic membrane pressure sensor, the minimum and maximum displacement is 0.03539mm and 0.03826mm respectively.

Thesis (M.S.)--University of Wisconsin--Madison, 1989.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 11-12).

碩士
國立暨南國際大學
電機工程學系
102
ZnO is one of the piezoelectric materials in which a voltage can be generated when a mechanical forces is applied. In this work, attempt was made to find out the feasibility of using ZnO nanorods as a pressure sensor. The ZnO nanorods used in this work were grown by hydrothermal method on Si substrate. Mechanical force applied to the ZnO nanorods array was achieved by pressing the nanorods with human fingers .Piezoelectric effect of ZnO nanorods prepared with different growth times and post-growth annealings was studied. We also investigated the effect of the distance between probes as well as the fingers’ position with respect to the probe. Our experimental results show that more voltage was generated when the distance between probes is farther separated, while the generated voltage becomes smaller as the fingers’ position was placed farther from the probe, Interestingly, the polarity of the generated voltage reverse when the ZnO nanorods were subjected to post-growth annealing. In this thesis, the experimental results observed were explained by the existing theory.

碩士
國立臺北科技大學
製造科技研究所
93
A low cost pressure sensor used in plastic injection die is developed in this study. A lot of efforts were exerted for this design to achieve three targets: 1. reduction of the production cost, 2. includes certain circuit units inside sensor with body being small and light, 3. preserve the deserved mechanical characteristics. Adopt typical CAE and CAD packages to perform simulations and analysis for a designing sensor. It is analyzed that the project includes：1. probe buckling, 2.contact analysis between probe and piezocrystal, 3. modal analysis for the probe and integral structure. 4. responses of harmonic exciting as well as step load. After a succession of evaluation, analysis, test and rectification. There have three kind of pressure sensors could be met the requirement：Ⅰ、Probe type with integrated charge amplifier. Ⅱ、Simple probe type without integrated charge amplifier. Ⅲ、Closed cap pressure sensor. Finally a solid of prototype sensor is made, but the fabricating cost is lower than 15000 NT dollars.

碩士
國立臺北科技大學
製造科技研究所
95
This research is to improve the second generation of mold cavity pressure sensor which was made by oneself and a new pressure sensor is designed, in this paper, which are called the third generation pressure sensor, the fourth generation pressure sensor and the fifth generation pressure sensor . There are three shortcomings in the second generation of pressures sensor: First, in the working environment is tested, when rising hurriedly in pressure, because the strength of structure is insufficient so the piezocrystal is easy to crack. Second, insulation is bad, it is easy to the short circuit and lose function. Third, the machining accuracy is insufficient, it is unstable to cause the response of the piezocrystal. To three disappearances, in this study, the structure of piezocrystal is improved as follows：Utilize insulation of ceramics and rigidity is strong to as the piezocrystal structure. Utilize insulation of the Teflon and its high-temperature characteristic, combine the spring to buffer, prevent the piezocrystal structure from shorting out, cracking and malfunctioning. Utilize the Teflon to make the piezocrystal structure，combine with the spring washer as the inside structure of the pressure sensor to protect the pressure sensor. The third generation pressure sensor , the fourth generation pressure sensor and the fifth generation pressure sensor both do the static, dynamic analysis of structural mechanics, including the working stress analysis of pressure sensor , the relation that the pressure corresponds with what the voltage outputs in the mold, natural frequency, modal shape and transient analysis. It is known by the analysis result that theirs mechanical characteristic are fine, the third generation pressure sensor make test result to be good , the fourth generation pressure sensor and the fifth generation pressure sensor are only analyzed, according to the analysis, natural frequency can reach 1.7kHz and 10 kHz, it can promote the range of working frequency while survey pressure.

The interest and need in portable, comfortable and durable health care sensors have increased along the years, due to their practicability and potential in helping people monitoring their vital signs. However, an all biodegradable low-cost sensor still poses a challenge to fabricate. So, cellulose is being used in the nanoscale form, due to filling all the necessary requirements with their excellent properties. The same can be said for metals like gold, silver and copper, which in the form of nanowires makes them great alternatives as sensing materials for pressure sensors. This work aims to develop a facile craft, low-cost, completely biodegradable, paper-based flexible and wearable pressure sensor for health care. The AgNWs are produced by the microwave-assisted polyol synthesis and purified with 3 decantation phases. The sensor substrate is made by pressing the bacterial nanocellulose (BNC) of nata de coco. The interdigitated electrodes (IDEs) are then screen-printed on its surface. The tissue paper is dip coated with the AgNWs, placed in the middle of the IDEs and encapsulated with the BNC, concluding the sensor construction. The sensor displayed a fast response time of 1.8 ms, a recovery time of 0.8 ms and it also showed high stability during 15000 cycles. The best sensitivity values achieved were 12.05 kPa-1 (0.031-1.4 kPa), 4.29 kPa-1 (1.4-2.8 kPa), 1.59 kPa-1 (2.8-5.6 kPa) and 0.38 kPa-1 (5.6-14 kPa), with the 6 dip coating cycles paper Tork on the sensor. The lowest detectable pressure was 31 Pa and the minimum and maximum energy consumption values recorded were 3.75×10-5 W and 1.32×10-2 W with a 2V working voltage.
O interesse e a necessidade em sensores de saúde portáteis, confortáveis e duráveis têm aumentado ao longo dos anos, devido à sua praticabilidade e potencial em ajudar as pessoas a monitorizarem os seus sinais vitais. No entanto, a produção de um sensor completamente biodegradável de baixo custo ainda representa um desafio. Por isso, vários tipos de celulose estão a ser usados à nanoescala por preencherem os requisitos necessários com as suas excelentes propriedades, assim como metais como o ouro, prata e cobre, que na forma de nanofios os torna ótimas alternativas como materiais de deteção em sensores de pressão. Este projeto tem como objetivo desenvolver um sensor de pressão fácil de fabricar, de baixo custo, completamente biodegradável, à base de papel, flexível e de fácil uso em cuidados de saúde. Os nanofios de prata são produzidos pela síntese poliol assistida por micro-ondas e purificados em 3 fases de decantação. O substrato do sensor é criado pressionando a nanocelulose bacteriana da nata de coco. Os elétrodos interdigitais são produzidos na sua superfície por impressão em tela. O papel é revestido com nanofios de prata por imersão, colocado no meio dos elétrodos interdigitais e encapsulado com a nanocellulose bacteriana, concluindo assim a construção do sensor. O sensor apresentou um rápido tempo de resposta de 1.8 ms, um tempo de recuperação de 0.8 ms e uma elevada estabilidade durante 15000 ciclos. Os melhores valores de sensibilidade obtidos foram 12.05 kPa-1 (0.031-1.4 kPa), 4.29 kPa-1 (1.4-2.8 kPa), 1.59 kPa-1 (2.8-5.6 kPa) e 0.38 kPa-1 (5.6-14 kPa) com o sensor a utilizar 6 ciclos de revestimento por imersão no papel Tork. O sensor também conseguiu detetar uma baixa pressão de 31 Pa e apresentou um consumo mínimo e máximo de energia de 3.75×10-5 W e 1.32×10-2 W, com uma tensão de trabalho de 2V.

The sensor is a device that converts a form of energy concerning which the information is sought, called the measurand, to a form (electrical) in which it can be usefully processed or interpreted. Sensors rely on physical or chemical phenomena and materials where those phenomena appear to be useful. Those phenomena may concern the material itself or its geometry. Hence, the major innovations in sensors come from new materials, new fabrication techniques or both. Normally, thin film sensors are realized by depositing a sensing film on a suitable substrate. There could be many combination of metals and insulating materials being deposited depending upon the application or sensing requirements. In general, sensors for various applications are fabricated using a variety of liquid phase technologies (also called as wet methods) and gas phase technologies (also called as dry methods) of deposition. Hence sensor fabrication technology requires various combination of processing technologies and newer materials. In the present work, an attempt is made to design and fabricate a thin film based pressure sensor using a combination of wet and dry deposition techniques. The diaphragm, used for sensing the pressure is coated with a hard anodic coating (Al2O3) using a wet technology, viz. pulse hard anodizing technique, for electrical insulation requirement. The piezo-resistive strain sensing films were deposited onto this coating by dry method, namely, DC Magnetron sputtering technique.. Chapter 01 gives a brief overview of sensors, their classification, principles of sensing,characteristics, materials used in the fabrication of sensors like conductors and insulators, the components of a sensor. Chapter 02 gives brief information about various techniques of depositions viz., liquid phase technologies (wet methods) and vapour phase technologies (dry methods) used to fabricate the sensors. Also, information regarding the coating property evaluation and coating characterization techniques is included. The chapter 03 presents a detailed account of work carried out to obtain an electrically insulating layer by the development of pulse hard anodizing process for aluminum alloy diaphragm, necessary process optimization and testing. The details related to the development, fabrication and testing of thin film based pressure sensors using aluminum alloy diaphragm with hard anodic coating are presented in Chapter 04. The thin film strain gauges were deposited using DC magnetron sputtering technique. The information about mask design, deposition process parameters, calibration etc is also included. Chapter 05 provides summary of the work carried out and conclusions. The scope of carrying out further work is also outlined.

碩士
雲林科技大學
電子與資訊工程研究所
96
This paper starts with basic theorem of parallel plate capacitor and classical theorem of plate and tries to calculate several kinds of capacitive structure with the combination of pre-readout sensing circuit and signal processing system circuit on a single chip, the aim is the design and fabrication of fully integrated capacitive micro-pressure sensor that can be detected pressure for airtight structure of industrial and biomedical application, and the geometry structure of capacitive pressure sensor is circle and rectangle. Each the pressure sensor has capacitive cells, and the sacrifical layers made by dry and wet etching for releasing structure. The HSPICE of software is used to evaluate the characteristics of the circuits, and the ANSYS of software is utilized to simulate the behaviors of the capacitive pressure sensor. The capacitive pressure sensor is sent to CIC for examination, then to TSMC for chip-size fabrication, after post-process uses dry and wet etching to remove sacrificial layers. Regardless of both etching method which are designed with the consideration of compatible standard process, and this paper rich experiences of using dry and wet etching techniques in post-process could be reliable references for releasing MEMS pressure sensor.