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Mechanics of micro-capacitive accelerometer with u-shape cantilever beam /Wang, Lin. January 1900 (has links)
Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2005. / Word processed copy. Summary in English and Chinese. Includes bibliographical references. Also available online.
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Probe characterisation, design and evaluation for the real-time quality indication of milk /Van der Westhuyzen, Petrus Johannes. January 2007 (has links)
Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.
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Soil moisture determination using a multisensor capacitance probe a laboratory calibration.Hyland, Raymond A. January 1999 (has links)
Thesis (M.S.)--Ohio University, November, 1999. / Title from PDF t.p.
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Wideband modelling of capacitive voltage sensors for open-air transmission line applicationsSchilder, Melanie 12 1900 (has links)
Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: This dissertation considers the wideband modelling of capacitive voltage sensors for open-air transmission
line applications. Two novel topologies were introduced, namely a differential parallel
plate sensor with a floating faraday cage for the interface instrumentation and a coaxial sensor
mounted around the earth conductor with a faraday cage connected to the earth conductor. The
modelling and analysis procedures included the derivation of equivalent circuit models in order to
simulate the calibration factor, the loading effect of the interface instrumentation and the effect of
leakage to ground, both in the time- and frequency domain.
In order to obtain a flat frequency response from very low frequencies (less than 5 Hz) to very
high frequencies (several MHz) it is important that the interface instrumentation have a high input
impedance and galvanic isolation be maintained. This was achieved by developing interface
instrumentation with a fibre-optic link operated from battery power. The instrumentation represents
a fairly unique approach in that the data is digitised before transmission across the serial
fibre-optical link, where-as conventional interfaces use analogue optical technology. Despite the
added complexity and high power requirements introduced by the digitising process, the improved
versatility is expected to yield a superior interface solution. The instrumentation has a bandwidth
of approximately 6 MHz, with an optional anti-aliasing filter at 1 MHz.
Special consideration should be given to the support structure as any unbalanced leakage to ground
will introduce variations in the frequency response towards the low-frequency end. Leakage of a
100 MQ was found to influence the frequency response of the circuit up to frequencies of 1 kHz.
Extensive simulation studies were conducted to obtain qualitative and quantitative insight into
the differential sensor topology and the associated electric fields. The improvement of a differential
plate sensor over the traditional single element plate sensor was demonstrated using twodimensional
simulations. Further simulations with a three-dimensional package showed that the
two-dimensional simulations are insufficient, because the boundary conditions and end effects have
a great influence on the calibration factor of the sensor.
Extensive laboratory tests were also undertaken to evaluate the sensor topology as well as the effects
of the interface instrumentation and leakage to ground. Excellent correlation were found
between the measured and simulated waveforms, both in the time- and frequency domains regarding
the calibration factor as well as the added poles or zeros at low frequencies. It can therefore
be deduced that a valid circuit model was suggested for these sensor topologies in the frequency
range from 10 Hz to 1 MHz.
Keywords: Capacitive sensors, Open-air voltage sensors / AFRIKAANSE OPSOMMING: Hierdie verhandeling beskou die wyeband modellering van kapasitiewe spanningsensors vir opelug
transmissie lyn toepassings. Twee oorspronklike topologieë is voorgestel, naamlik 'n differensiële
parallel plaat sensor met 'n aparte faraday hok vir die koppelvlak instrumentasie en
'n koaksiale sensor wat rondom die aardgeleier monteer word met die faraday hok ook aan die
aardgeleier gekoppel. Die modellerings en analise prosedures het ingesluit die afleiding van ekwivalente
stroombaanmodelle vir simulasie van die kalibrasiefaktor asook die belasingseffek van
die koppelvlak instrumentasie en lekweerstand na grond in beide die tyd- en frekwensie gebiede.
Om 'n plat frekwensieweergawe te verkry vanaf baie lae frekwensies (laer as 5 Hz) tot by baie
hoë frekwensies Cn paar MHz), is dit belangrik dat die koppelvlak instrumentasie 'n hoë intreeimpedansie
het en galvaniese isolasie verseker word. Dit was bereik deur koppelvlak instrumentasie
te ontwikkel met 'n optiese vesel koppeling wat met battery krag aangedryf word. Die instrumentasie
verskaf 'n redelik unieke aanslag in die opsig dat die data gemonster word voordat
dit oor die seriële optiese vesel skakel gestuur word, terwyl konvensionele koppelvlakke analoog
optiese tegnologie gebruik. Ten spyte van die toegevoegde kompleksiteit en hoë drywingsvereistes
van die versyferingsproses, het die instrumentasie se veelsydigheid toegeneem tot die mate dat dit
as 'n beter koppelvlak oplossing beskou word. Die instrumentasie het 'n bandwydte van ongeveer
6 MHz, met 'n opsionele teen-vou filter by 1 MHz.
Die ondersteuningstruktuur is van besondere belang aangesien enige ongebalanseerde lekweerstand
na grond afwykings in die frekwensieweergawe sal veroorsaak aan die lae frekwensie kant.
Lekweerstand van 100 MQ sal die frekwensieweergawe beïvloed tot by ongeveer 1 kHz.
Uitgebreide simulasies is gedoen om kwalitatiewe en kwantitatiewe insig in die differensiële sensor
topologie en die geassosieerde elektriese velde te verkry. Die verbetering van 'n differensiële
parallel plaat sensor in vergelyking met die tradisionele enkel element plaat sensor is demonstreer
met twee-dimensionele simulasies. Verdere simulasies met 'n drie-dimensionele pakket het gewys
dat die twee- dimensionele simulasies onvoldoende is aangesien grensvoorwaardes en randeffekte
'n groot invloed het op die kalibrasiefaktor van die sensor.
Uitgebreide laboratorium toetse is ook gedoen om die sensor topologie sowel as die effekte van die
koppelvlak instrumentasie en lekweerstand na grond te evalueer. Uitstekende korrelasie is gevind
tussen gemete en voorspelde golfvorms, in beide die tyd- en frekwensie gebied met betrekking tot
die kalibrasie faktor sowel as die toegevoegde pole en zeros by lae frekwensies. Die gevolgtrekking
is dus dat 'n geldige stroombaanmodel voorgestel is vir die sensor topologieë vir die frekwensie
bereik van 10Hz to 1 MHz.
Sleutelwoorde: Kapasitiewe sensors, Ope-lug spanningsensors
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Comparison of noise performance of capacitive sensing amplifiersStrait, Thomas J. January 2006 (has links)
Thesis (M.S.)--State University of New York at Binghamton, Department of Electrical and Computer Engineering, 2006. / Includes bibliographical references.
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Procedure for determining the stray capacitance of a switching circuit nodeNaude, Tonya 26 February 2009 (has links)
M.Ing. / This study focuses its attention on conducted common mode EMI. Common mode current is the current that flows from an electrical circuit to a zero reference plane and back to the circuit again. It is known that the manner in which the common mode current flows is through stray capacitances that form between the electrical circuit and the zero reference. This study was aimed at developing a method to measure the value of the stray capacitance of a switching circuit. Determining the value of the stray capacitance by taking physical measurements on a circuit board is a challenge for a number of reasons, one of which is that great care should be taken not to add to the stray capacitance by means of the measuring equipment. By measuring the value of the stray capacitance, it will be possible to model the occurrence of Common Mode EMI better and more accurately. This could, in turn, lead to a reduction in EMI. Any body of an arbitrary shape, size and material exhibits a self-capacitance with respect to a zero reference frame. This principle, together with the principle of conservation of charge, also applies to electrical components, or circuits as a whole. The experimental work was performed on a buck DC-DC converter. The circuit was simplified to aid in analysis. By varying the value of an external capacitance and taking basic measurements, it is then possible to uniquely determine the absolute values of the self-capacitances. For every pair of external capacitance values placed in the circuit (of which one can be =0pF), a value for stray capacitance is calculated. Many data points were recorded with many different external capacitors in the circuit, resulting in a variety of stray capacitance values. In order to obtain a single value, a weighted mean of all the values was calculated. The values obtained in this proposed method of measuring the stray capacitance compares well with that obtained using the Finite Element Method. The advantage of the method presented here is that the self-capacitances are determined under the actual operational conditions, no specialised equipment is required and no unique handling of parasitics is needed. The method relies on very simple measurements and no complex data manipulations are required.
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Probe characterisation, design and evaluation for the real-time quality Indication of milkVan der Westhuyzen, Petrus Johannes 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / In order to rapidly detect, monitor and predict changes in milk as it ferments, sensors would need to be
designed specifically for milk. To this end, invasive surgical stainless steel probes were investigated and
the probe impedances were characterised according to measurements made in various saline concentrations.
Based on these findings, specific probes were designed that were robust and easy to use in milk.
To measure multiple probe sensors continuously and accurately, an automatic measurement device was
designed and manufactured. The device was self-sustaining, portable and calculated and stored all probe
impedance data internally, allowing experimental runs to take place in controlled laboratory environments.
The probes designed in this thesis were consequently tested in various milk fermentation experiments
and it was found that surgical stainless steel probes were effective at detecting and monitoring fermentation
changes. The probe impedance changes also lead the pH changes in milk, giving it a predictive element.
The probe sensor studies provided enough data so that studies could be done into potential non-invasive
sensors. Therefore, capacitive sensors were investigated and a fringe field capacitor was presented as a
potential non-invasive milk fermentation sensor.
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Development of a binary mixture gas composition instrument for use in a confined high temperature environmentCadell, Seth R. 28 November 2012 (has links)
With recent advancements in material science, industrial operations are being conducted at higher and higher temperatures. This is apparent in the nuclear industry where a division of the field is working to develop the High Temperature Gas Reactor and the Very High Temperature Gas Reactor concurrently. Both of these facilities will have outlet gas temperatures that are at significantly higher temperatures than the typical water cooled reactor. These increased temperatures provide improved efficiency for the production of hydrogen, provide direct heating for oil refineries, or more efficient electricity generation. As high temperature operations are being developed, instruments capable of measuring the operating parameters must be developed concurrently. Within the gas reactor community there is a need to measure the impurities within the primary coolant. Current devices will not survive the temperature and radiation environments of a nuclear reactor. An instrument is needed to measure the impurities within the coolant while living inside the reactor, where this instrument would measure the amount of the impurity within the coolant.
There are many industrial applications that need to measure the ratio of two components, whether it be the amount of particulate in air that is typical to pneumatic pumping, or the liquid to gas ratio in natural gas as it flows through a pipeline. All of the measurements in these applications can be met using a capacitance sensor. Current capacitance sensors are built to operate at ambient temperatures with only one company producing a product that will handle a temperature of up to 400 °C. This maximum operating temperature is much too low to measure the gas characteristics in the High Temperature Gas Reactor. If this measurement technique were to be improved to operate at the expected temperatures, the coolant within the primary loop could be monitored for water leaks in the steam generator, carbon dust buildup entrained in the flow, or used to measure the purity of the coolant itself.
This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined
environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core. / Graduation date: 2013
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