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Goparaju, SravanthiLow Power Tire Pressure Monitoring System
Master of Science, University of Akron, 2008, Electrical Engineering

Power management is considered to be an important aspect in designing battery operated Tire Pressure Monitoring Systems (TPMS) as it helps to prolong the lifespan of the battery. There are several methods that can be used to design a low power tire-pressure and service monitoring system. One of the most common methods for power reduction is the duty cycle method. This thesis suggests an idea of implementing the TPMS in combination with a separate Radio Frequency Identification (RFID) circuit, especially a very low power (active or passive) RFID whose sole purpose is to detect the interrogating signal. This RFID circuit which can operate at a typical frequency of 125 kHz is used to turn ON a higher power transmitter which is initially in SLEEP state and soon after entering the active state performs the communication, updating, etc. Once the desired task is completed, the high power transmitter returns to SLEEP state or is turned off until the next interrogation.

The implementation of SLEEP mode to minimize power consumption is discussed in detail and the currents consumed by the microcontroller in SLEEP and ACTIVE modes are measured and recorded. The microcontroller in SLEEP mode consumed a current of 17μA which reduced the overall average current consumed by the microcontroller and the pressure sensor. Furthermore, this method promises an improvement in the battery life and the calculations showing this improvement are discussed with the example of an AA battery with 2800mAh battery life.

Committee:

Nathan Ida (Advisor)

Subjects:

Electrical Engineering

Keywords:

TPMS; RFID; TIRE; pressure sensor; microcontroller; TIRE PRESSURE; sensor

Majerus, Steve JWireless, Implantable Microsystem for Chronic Bladder Pressure Monitoring
Doctor of Philosophy, Case Western Reserve University, 2014, EECS - Electrical Engineering
This work describes the design and testing of a wireless implantable bladder pressure sensor suitable for chronic implantation in humans. The sensor was designed to fulfill the unmet need for a chronic bladder pressure sensing device in urological fields such as urodynamics for diagnosis and neuromodulation for bladder control. Neuromodulation would particularly benefit from a wireless bladder pressure sensor providing real-time pressure feedback to an implanted stimulator, resulting in greater bladder capacity while using less power. The pressure sensing system consists of an implantable microsystem, an external RF receiver, and a wireless battery charger. The implant is small enough to be cystoscopically implanted within the bladder wall, where it is securely held and shielded from the urine stream, protecting both the device and the patient. The implantable microsystem consists of a custom application-specific integrated circuit (ASIC), pressure transducer, rechargeable battery, and wireless telemetry and recharging antennas. Because the battery capacity is extremely limited, the ASIC was designed using an ultra-low-power methodology in which power is dynamically allocated to instrumentation and telemetry circuits by a power management unit. A low-power regulator and clock oscillator set the minimum current draw at 7.5 µA and instrumentation circuitry is operated at low duty cycles to transmit 100-Hz pressure samples while consuming 74 µA. An adaptive transmission activity detector determines the minimum telemetry rate to limit broadcast of unimportant samples. Measured results indicated that the power management circuits produced an average system current of 16 µA while reducing the number of transmitted samples by more than 95% with typical bladder pressure signals. The wireless telemetry range of the system was measured to be 35 cm with a bit-error-rate of 10-3, and the battery was wirelessly recharged at distances up to 20 cm. A novel biocompatible packaging method consisting of a silicone-nylon mesh membrane and a compliant silicone gel was developed to protect the sensor from water ingress while only reducing the sensor sensitivity by 5%. Dynamic offset removal circuitry extended the system dynamic range to 2,900 cm H2O but limited the sensor AC accuracy to 3.7 cm H2O over a frequency range of 0.002 – 50 Hz. The DC accuracy of the sensor was measured to be approximately 2.6 cm H2O (0.9% full-scale). Functionality of wired prototypes was confirmed in feline and canine animal models, and wireless prototypes were implanted in a female calf large-animal model. Measured in vivo pressure recordings of bladder contractions correlated well with reference catheters (r =0.893–0.994).

Committee:

Steven Garverick (Advisor); Swarup Bhunia (Committee Co-Chair); Margot Damaser (Committee Member); Pedram Mohseni (Committee Member); Christian Zorman (Committee Member)

Subjects:

Biomedical Engineering; Electrical Engineering

Keywords:

Implantable electronics; bladder pressure sensor; low-power; integrated circuit; wireless; chronic implantation; bladder implant; pressure sensor; power management; adaptive transmission rate; wireless battery recharge

Abbas, Syed FarhatDevelopment of a low cost shock pressure sensor
Master of Science (MS), Ohio University, 1988, Mechanical Engineering (Engineering)
Development of a low cost shock pressure sensor.

Committee:

Jay Gunasekera (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Shock Pressure Sensor; Determination of Hugoniot Curve; Piezoelectric Polymers

Birck, Matthew D.TEMPORAL VARIABILITY OF RIVERBED HYDRAULIC CONDUCTIVITY AT AN INDUCED INFILTRATION SITE, SOUTHWEST OHIO
Master of Environmental Science, Miami University, 2006, Environmental Sciences
This study investigated the impact of high-stage events on riverbed scour and hydraulic conductivity (Kv). Seepage-meter measured riverbed Kv averaged 0.092 m/d. Slug-test measured Kv of the underlying sediment averaged 9.6 m/d. The low riverbed Kv is probably due to a gravel and cobble layer clogged with fine sediment (colmation layer). Kv of cores of transient material overlying the cobble layer averaged 5.3 m/d. Event-driven scour, measured with cross-sectional profiles, scour chains, and a load-cell pressure sensor, never exceeded 0.06 m, indicating that the colmation layer remained intact, despite even a 60-year event. A riverbed conceptual model of three distinct layers –transient sediment, an armor/colmation layer and a transitional bottom – had an overall Kv of 4.6 m/d. Sensitivity analysis of layer thicknesses indicated that a) the transient layer has negligible impact on the overall Kv and b) loss of the colmation layer, while not observed, could double the overall Kv.

Committee:

Jonathan Levy (Advisor)

Keywords:

riverbed; hydraulic conductivity; seepage meter; colmation; armor; load-cell pressure sensor; scour; riverbank filtration; LT2ESWTR

Scardelletti, Maximilian CDEVELOPMENT OF A HIGH TEMPERATURE SILICON CARBIDE CAPACITIVE PRESSURE SENSOR SYSTEM BASED ON A CLAPP-TYPE OSCILLATOR CIRCUIT
Doctor of Philosophy, Case Western Reserve University, 2016, EECS - Electrical Engineering
In this dissertation, the development of a packaged silicon carbide (SiC) based MEMS capacitive pressure sensor system that is designed to monitor the pressure of a conventional gas turbofan engine is described. The electronic circuit of the pressure sensor system is based on a Clapp-type oscillator that includes a 6H-SiC MESFET, a SiCN MEMS-based capacitive pressure sensor, titanate MIM capacitors, wirewound inductors, and thick film resistors. The capacitive pressure sensor is incorporated in the LC tank circuit of the oscillator so that a pressure-induced change in capacitance causes a change in the resonant frequency of the oscillator. The MESFET is used to induce oscillation. Individual passive components were evaluated at high temperature to assess their utility in an integrated system. Both wireless and wired variants of the pressure sensor systems for use at high temperature were developed. In developing the final packaged device, several prototype designs of the Clapp-type oscillator circuit that incorporate wireless capability were explored. Prototype circuits with slot-ring and chip antennas operating between 700 MHz and 1 GHz exhibited a maximum operating temperature of 250¿C, limited by the low gain of the MESFET at these frequencies. Prototype circuits operating at 30 and 90 MHz that utilize large spiral inductors in the Clapp oscillator as the radiating element extended stable operation to 470°C. Several wireless pressure sensor prototypes based on the Clapp oscillator circuit were developed. A prototype incorporating a polysilicon capacitive pressure sensor and a spiral inductor exhibited stable operation up to 300°C. A second prototype that used a SiCN capacitive pressure sensor functioned at temperatures up to 400°C. A third prototype based on the 2nd prototype but incorporating a compact, directional chip antenna had a maximum operating temperature of 300ºC, limited by the antenna. Based on size restrictions, the packaged system utilized a wired configuration. This prototype operates reliably from 0 to 350 psi and from 25 to 540°C, with a sensitivity of 6.8x10-2 MHz/psi and negligible difference in frequency response. The packaged sensor passed standard benchtop temperature, pressure and vibration acceptance tests required prior to any future test on a flight worthy engine.

Committee:

Christian Zorman, Dr. (Advisor)

Subjects:

Engineering

Keywords:

Silicon carbide, capacitive pressure sensor, wireless

Abeysinghe, Don ChandanaNovel MEMS Pressure and Temperature Sensors Fabricated on Optical Fibers
PhD, University of Cincinnati, 2001, Arts and Sciences : Physics
This thesis presents the design, fabrication, and testing of novel MEMS pressure and temperature sensors fabricated on optical fiber end faces. A simple micromachining process compatible with MEMS was developed in fabricating sensors directly on optical fibers. The pressure sensor configuration involves anodic bonding of a piece of an extremely thin silicon wafer onto the fiber end face over a cavity etched in the central portion of the fiber end face. Final device diameter is thus the same as that of the optical fiber. The temperature sensor is based on anodically bonding a thin piece of silicon onto the fiber end face.The pressure sensors were fabricated on 400 um diameter fibers while temperature sensors were fabricated on both 200 and 400 um diameter fibers. Pressure measurements were made over the 14 to 80 psi range while temperature measurements were made over the 23 to 300 Celcius range. Pressure sensor sensitivities of 0.1 mV/psi and 0.2 mV/psi were obtained. The pressure sensors were designed with cavity diameter d=150 um, and cavity depth h=0.640 um. Diaphragm thickness for the two sensors were t=7.1, and t=3.4 um. Higher sensitivity was achieved by design of a sensor with the thinner diaphragm. A sensor array fabrication effort demonstrated that our micromachining process could be extended to simultaneous processing of an array of fibers. The temperature sensor was fabricated by bonding 3.1 um thick silicon onto the fiber end face. An oxidant-resistant encapsulation scheme for the temperature sensor was proposed, namely aluminum coated silicon nitride (Al/Si3N4). The uncoated side of silicon was bonded to a fiber end face using the anodic bonding method. The measured values of kf=(lambda)-1x(dlambda/dT) for capped and uncapped sensors were kf=(7.5±0.6)x10-5/Celcius, and kf=(7.2±0.1)x10-5/Celcius respectively. The measured kf value for the uncapped sensor is equal to that which was determined using the published material properties for crystalline silicon (kf=7.9x10-5/Celcius) within measurement uncertainty. The micromachining process developed for micromachining fiber end faces along with the bonding of silicon to fiber end faces can be extended to fabrication of other MEMS based micro-optic devices where fiber optic interrogation is advantageous.

Committee:

Howard Jackson (Advisor)

Keywords:

PRESSURE SENSOR; TEMPERATURE; MEMS; FIBER OPTIC SENSOR; FABRY-PEROT SENSOR

Ho, Shih-ShianStainless Steel Capacitive Pressure Sensors for Harsh Environment Applications
Doctor of Philosophy, Case Western Reserve University, 2012, Materials Science and Engineering
This dissertation explores the development of a new stainless steel pressure sensor capable of sustaining harsh environments, including high pressures, high temperatures, and/or corrosive media. The proposed pressure sensor utilizes commercial off-the-shelf (COTS) components, adapts vacuum coupling radiation (VCR) tube fitting (Swagelok Co.) for sensor packaging, and combines micro- and conventional-machining techniques for sensor realization. Capacitive transduction is used to simplify the implementation, as well as take advantage of the high stability and low temperature drift associated with this transduction scheme. Two generations of stainless steel capacitive pressure sensors have been developed in this dissertation. The first-generation sensor is comprised of a stainless steel diaphragm die and a stainless steel backing plate, each electrically isolated with tetraethylorthosilicate (TEOS) silicon dioxide, and packaged by a set of COTS VCR tube fitting. The pressure sensor responses show four operating regions, including stabilizing, non-touch, transition, and touch mode regions. The fully packaged pressure sensor is characterized at high pressures of up to 10,340 kPa (1,500 psi) and at high temperatures of up to 300°C. Corrosive pressure media, including potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) solutions, are used to demonstrate the corrosive-media compatibility of the pressure sensor. After soaking in these corrosive media and several tens of pressure cycles over a month, the fully packaged pressure sensor continues to show stable and consistent operation. Because of the anomalous stabilizing region in these sensors, sensor-to-sensor variance is very poor (i.e., 62% in full-scale (FS)). The second-generation sensor is developed to address the shortcomings found in the first-generation pressure sensor. A hard tungsten carbide backing plate used to replace the stainless steel backing plate and a stainless steel press plate are used to eliminate the stabilizing region found in the first-generation sensor. Three typical operating regions, including non-touch mode, transition, and touch mode regions, are achieved in the sensor operation. Without the stabilizing region, the sensor-to-sensor variance is improved to 9% FS. The fully-packaged pressure sensor is operated in high pressures of up to 6,900 kPa (1,000 psi), at high temperatures of up to 320°C, and/or in corrosive media, including KOH and sodium chloride (NaCl) solutions. In addition, the pressure sensor is operated 1+ million pressure cycles in the pressure range of 0-4,830 kPa (0-700 psi) at room temperature to demonstrate its lifetime and reliability. In addition, the relationship of deposition conditions and properties of the TEOS silicon dioxide film is investigated using analysis of variance (ANOVA). The chemical composition of TEOS oxide is investigated using X-ray photoelectron spectroscopy and etch rate experiments. Finally, metal-insulator-metal test structures are fabricated to characterize the dielectric properties of TEOS oxide film at elevated temperatures.

Committee:

Mehran Mehregany (Advisor); Frank Ernst (Committee Member); Pirouz Pirouz (Committee Member); Harold Kahn (Committee Member)

Subjects:

Engineering

Keywords:

stainless steel; capacitive pressure sensor

LI, CHUNYANPOLYMER FLIP-CHIP BONDING OF PRESSURE SENSORS ON FLEXIBLE KAPATON FILM FOR NEONATAL CATHETERS
MS, University of Cincinnati, 2004, Engineering : Electrical Engineering
The object of this thesis is to develop a new packaging method to mount silicon micro pressure sensors into 1.67 mm diameter neonatal catheters to measure blood pressure. A new polymer flip-chip bonding method on a flexible Kapton film has been developed and applied to dual lumen neonatal catheters integrated with silicon micro pressure sensors. Flip chip bonding technique has inherent advantages of miniaturization, improved reliability and cost reduction. This polymer flip-chip bonding technique requires a low temperature process and improved tolerance of thermal stress which are very desirable for mounting micro sensors or micro actuators on lower-cost flexible polymer substrates for medical applications. The silicon micro pressure sensors, which are mounted on a flexible Kapton film with metal lines for neonatal catheter, have been fully characterized in both gas and liquid environments, indicating that the packaging was satisfactory rugged for catheter use.

Committee:

Dr. Chong H. Ahn (Advisor)

Keywords:

polymer flip-chip bonding; piezoresistive pressure sensor; neonatal catheter