Spelling suggestions: "subject:"chineseelectronic engineering."" "subject:"chineseelectronic ingineering.""
281 |
A zinc oxide nanowire pressure sensorVan den Heever, Thomas Stanley 12 1900 (has links)
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.
|
282 |
The development of carbon nanostructured sensorsKritzinger, Pieter Christo 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: During this research the possibility of using carbon nanostructures in sensors
were investigated. Graphene and carbon nanotubes (CNTs) are the nano-
structures that were used in the developed sensors. Graphene is a single
atomic layer of carbon and a carbon nanotube (CNT) is a rolled up sheet of
graphene that forms a tube. The unique structure and incredible properties
of both these materials make them ideal to be used in sensory applications. A
graphene sensor was developed and experiments were performed to determine
whether graphene is a viable candidate to be used in a wide range of sensory
applications. The graphene sensor operated successfully as a humidity sensor
and this led to the discovery that humidity can be used to control the bandgap
in graphene. The absorption of CO2 in graphene was successfully measured
using surface acoustic waves. As a result, any gas that graphene absorbs can be
detected using this method. The use of graphene in three liquid applications
was tested. The graphene showed no potential to be used as a pH sensor
or as a
ow sensor. An experiment was undertaken to determine whether
graphene can increase the e ciency of a water electrolysis process, but it
was established that the graphene does not make a signi cant di erence. A
CNT gas sensor that identi es a gas based on its ionization characteristics
was studied and designed. Due to the insu cient height of the grown CNTs,
it was decided to focus on the creation of a model of the sensor that can be
used to design it optimally. The results of the experiments con rmed that
carbon nanostructures such as graphene and CNTs have potential to be used
in future sensing applications. / AFRIKAANSE OPSOMMING: Hierdie navorsing ondersoek die moontlikheid om koolstof-nanostrukture in
sensor-apparate te gebruik. Grafeen en koolstof-nanobuisies (KNB) is die
nanostrukture wat in die ontwikkelde sensors gebruik is. Grafeen is 'n
enkel atomiese koolsto
agie en KNBs is 'n opgerolde grafeenlagie wat 'n
buisie vorm. Die unieke struktuur en ongeloo
ike eienskappe van beide
hierdie materiale, maak hulle uiters geskik om in sensor-toepassings gebruik
te word. 'n Grafeensensor is ontwikkel en eksperimente is uitgevoer om
te bepaal of grafeen 'n goeie kanidaat is om in 'n wye verskeidenheid van
toepassings gebruik te word. Die grafeensensor is suksesvol aangewend as
'n humiditeitsensor en dit het gelei tot die uitvindsel dat humiditeit gebruik
kan word om die energiegaping in grafeen te varieer. Die absorpsie van CO2
in grafeen is suksesvol gemeet deur oppervlak akoestiese golwe te gebruik.
Gevolglik kan enige gas wat grafeen absorbeer op hierdie manier gemeet word.
Die gebruik van grafeen is in drie vloeistof-toepassings getoets. Die grafeen
het geen potensiaal getoon om as 'n pH-sensor of as 'n vloei-sensor aangewend
te word nie. 'n Eksperiment is ook uitgevoer om te toets of grafeen die
e ektiwiteit van 'n water-elektroliese proses kan verhoog, maar die resultate
het gewys dat dit nie 'n wesenlike verskil maak nie. 'n KNB-gassensor, wat
'n gas identi seer uit die ioniseerings eienskappe van die gas, is bestudeer en
ontwikkel. Die lengte van die KNBs wat gegroei is, was onvoldoende en daar
is gefokus op die ontwerp van 'n model van die sensor wat gebruik kan word
om dit optimaal te ontwerp. Die resultate van die eksperimente het bevestig
dat koolstof-nanostrukture soos grafeen en KNB baie potentiaal het om in
toekomstige sensor-toepassings gebruik te word.
|
283 |
An experimental investigation into the validity of Leeson's equation for low phase noise oscillator designVan der Merwe, John 12 1900 (has links)
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: In 1966, D.B. Leeson presented his model on phase noise in a letter entitled A
Simple Model of Feedback Oscillator Noise Spectrum. This model usually requires
an additional e ffective noise figure in order to conform with measured results. (This
e ffective noise fi gure has to be determined by means of curve-fi tting Leeson's model
with the measured results.) The model is, however, relatively simple to use, compared
with other more accurate phase noise models that have since been developed
and which can only be solved numerically with the aid of computers. It also gives
great insight regarding component choices during the design process.
Therefore several experiments were conducted in order to determine conditions under
which Leeson's model may be considered valid and accurate. These experiments, as
well as the conclusions drawn from their results, are discussed in this document. / AFRIKAANSE OPSOMMING: In 1966 stel D.B. Leeson sy faseruis model bekend in 'n brief getiteld A Simple
Model of Feedback Oscillator Noise Spectrum. Hierdie model vereis gewoonlik die
gebruik van 'n bykomende e ektiewe ruissyfer, sodat die model ooreenstem met die
gemete resultate. (Hierdie e ektiewe ruissyfer kan slegs bepaal word deur middel van
krommepassings tussen Leeson se model en die gemete resultate.) Die model is egter
relatief eenvoudig om te gebruik in teenstelling met ander, meer akkurate, faseruis
modelle wat sedertdien ontwikkel is en slegs met behulp van rekenaars opgelos kan
word. Dit bied ook onoortre
ike insig ten opsigte van komponent keuses tydens die
ontwerpsproses.
Om hierdie rede is verskeie eksperimente uitgevoer met die doel om toestande te
identi seer waaronder Leeson se model as geldig en akkuraat geag kan word. Hierdie
eksperimente, asook die gevolgtrekkings wat van hul resultate gemaak is, word in
hierdie dokument behandel.
|
284 |
Probes in HF metrologyRossouw, Daniel Johannes 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Flanged coaxial probes are widely used to conduct accurate, broadband permittivity measurements
of various dielectric materials. A metrology study, discussed in [1], revealed that
small perturbations in measured permittivity data, are due to escaping common-mode (CM)
current that propagates onto exposed VNA feed cabling. This is not considered in published
permittivity extraction algorithms, like the National Institute of Standards and Technology
(NIST) full-wave code that assumes an infinite flange radius. To characterise this effect we
validate a finite volume time domain (FVTD) CST simulation model of an SMA coaxial
probe, by probing sensitive E-fields in a metallic shielding cylinder, placed around it.
For this process, electro-optic (EO) E-field sensors are considered and a Mach-Zehnder
type sensor is designed. Manufacturing difficulties discontinues this approach, but the revisited
extended centre conductor E-field probing technique proves successful. The technique
entails a high dynamic range, two-port VNA measurement. Through CST we gain
knowledge of the physics behind the CM-problem and the behaviour of fields around the
coaxial probe. Different shielding environments are simulated to establish their ability to
impede CM-current coupling onto measurement cabling.
To study the CM-effect on extracted permittivity results, the investigation is extended
to Short-Open-Load (SOL) calibrated face-plane measurements of dielectric solids. A CST
model, which considers escaping CM-energy, is used to generate open circuit (OC) calibration
coefficients and to serve as an independent extraction method. We inspect the effect
of different shielding environments and through CST, extract accurate permittivity results
for e00, to a degree not previously achieved for such systems. This allows comment on the
infinite-flange-radius assumption of the NIST method and proves the significance of the
CM-effect. / AFRIKAANSE OPSOMMING: Geflensde koaksiale probes word algemeen in die praktyk gebruik om akkurate, wyeband
permitiwiteitmetings van diëlektriese materiale te verrig. ’n Studie wat in [1] bespreek
word, dui aan dat klein verskynsels in gemete resultate, verband hou met gemene-modus
(GM) stroom, wat ontsnap en teenwoording is aan die buitekant van onbeskermde voerkabels.
Hierdie verkynsel word nie deur huidige volgolf ekstraksie-algoaritmes, soos die van
NIST wat ’n onëindige flensradius aanvaar, in ag geneem nie. Om die GM-effek te karakteriseer,
verifieer ons ’n eindige-volume tyd-gebied CST simulasiemodel, deur sensitiewe
metings binne ’n silidriese metaalskerm, wat om so ’n probe geplaas word.
Vir hierdie meting word elektro-optiese E-veld probes eers oorweeg. In gevolg word
’n Mach-Zehnder-tipe probe ontwerp, maar vervaardigingsprobleme en tyd-oorwegings
kniehalter hierdie benadering. Heroorweging van die verlengde koaksiale sentraalgeleier,
E-veld-probe tegniek, wat hoë dinamiese bereik twee-poort netwerkanaliseerder metings
behels, slaag uiteindelik in hierdie doel. CST maak dit nou moontlik om die GM stroomprobleem
te simuleer en spesefieke veldgedrag te kan waarneem. Verskillende afskermingsmetodes
se vermoë om GM-koppeling na kabels te beperk word ondersoek.
Die GM studie word uitgebrei na SOL-gekalibreerde, flensvlakverwysde permitwiteitmetings
van diëlektriese vastestowwe. ’n CST model, wat GM stroom in ag neem, word
gebruik om oopgeslote kalibrasiekofisiënte te genereer en dien ook as ‘n alternatiewe permitiwiteit
ekstraksiemetode. Die effek van die verskillende afskermingstegnieke word ondersoek
en deur die CST metode te gebruik, word ’n aansienlike verbetering in akkuraatheid
van e00 waardes verkry. Dit regverdig kommentaar oor die aannames wat in die NIST
metode gemaak word en beklemtoon die belangrikheid om GM stroom in ag te neem.
|
285 |
Hot electron bolometer sensors for millimetre-wave and terahertz wave detectionNortheast, David Bernard 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--Univerity of Stellenbosch, 2011. / ENGLISH ABSTRACT: The design and simulation of hot electron bolometer sensors for the detection
of millimeter and terahertz wave radiation is presented. These devices can be
used for the formation of images or for spectroscopy in these frequency ranges.
Many molecules resonate and have absorption spectra over these ranges, allowing
for the identi cation, non-destructively and at a distance, of the constitution
of many di erent materials. The penetrating ability of the radiation
makes mm-wave and THz wave detectors ideal for security imaging. The design
and simulation of these devices predicts performance as mixers and as
interferometers. Manufacturing processes used while fabricating these thin
lm devices are outlined and experimental results are reported. / AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die ontwerp en simulasie van warm-elektron bolometers
vir die waarneming van millimetergolf- en terahertz-straling. Sodanige
toestelle kan in bogenoemde frekwensiebereike gebruik word vir beeldvorming
of spektroskopie. Aangesien heelwat molekules binne hierdie bande resoneer,
kan die samestelling van 'n verskeidenheid materiale oor 'n afstand en op
'n nie-vernietigende wyse gedenti seer word. Die deurdringingsvermo van
millimetergolf- en terahertz-straling maak sulke detektors ideaal vir beeldvorming
in veiligheidstoepassings. Met die ontwerp en simulasie van hierdie
toestelle word gewys wat hul werkverrigting as mengers en interferometers kan
wees. Die prosesse wat gebruik is om hierdie dun lmtoestelle mee te vervaardig
word ook bespreek en eksperimentele resultate word aangebied.
|
286 |
The development of equipment for the fabrication of thin film superconductor and nano structuresButtner, Ulrich 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The nano-age is more about the mesoscopic phenomena, than those occurring at molecular
and atomic level, which have been studied by chemists and physicists for more
than a hundred years. Nanotechnology is currently one of the most active fields being
explored in many different disciplines by many scientists across the world. In this
research field, it is imperative to continually create more effective and superior methods
to build smaller and smaller electronic devices, circuits and sensors. Technology
is being improved continually and, specifcally at our university, there was a need to
improve our device manufacturing facility. The aim of this work was to create a new
sputtering system, build a dry etching system and to make modifications to upgrade
existing equipment. This work has been done to produce nano structures or devices
and, most importantly, to save costs.
New systems and equipment have been built to keep up with the progress in this field.
In order to understand the significance of the different types of equipment used in
the fabrication of thin film superconductor layers, an overview will be given of the
complete process of manufacturing a patterned Josephson junction. The apparatus
used will be described and critically analyzed, whereby the shortfalls in design will be
highlighted and improvements shown. Some of the equipment, such as the plasma laser
deposition system, the lithography system and the test facility existed before and has
been modified. Newly designed systems were built to further improve the quality of
our thin film superconductors; these include the inverted cylindrical magnetron (ICM)
sputtering system, the argon ion mill and the incandescent substrate heater.
Finally, the results of the improved thin films and structures will be shown. To summarize:
The entire process was analyzed and upgraded, resulting in an improved device
manufacturing facility. / AFRIKAANSE OPSOMMING: Die nano-era het aangebreek en nanotegnologie is tans een van die mees aktiewe en diverse
navorsingsvelde wat wetenskaplikes wêreldwyd ontgin - hoofsaaklik as gevolg van
nuwe verskynsels op molekulêre en atomiese vlak. In die nanotegnologie-navorsingsveld
is die vereiste dat daar voortdurend meer effektiewe metodes gevind moet word om die
al hoe meer miniatuurwordende elektroniese meganismes met verbeterde energieverbruik,
spoed en ruimtebesparende vermoëns tot stand te bring.
Dit is duidelik dat in hierdie toonaangewende navorsingsveld, waar tegnologiese ontwikkeling
voorturend en snelgroeiend is, dit dikwels vinniger is om reeds bestaande
toerusting aan te pas en te moderniseer ten einde in pas te bly met nuutontwikkelde
en ontwikkelende tegnologieë. Die doel van die werk verrig, wat hier beskryf word, was
om 'n nuwe deponeerstelsel, sowel as 'n droogets stelsel te bou. Bestaande apparaat is
opgradeer deur verandering aan te bring. Die uiteintelikke doel is die vervaarding van
beter nano-strukture, en terselfde tyd om kostes te bespaar.
Nuwe stelsels en toerusting is gebou om tred te hou met tegnologiese vooruitgang. Om
die belangrikheid van die verskillende tipes toerusting wat in die vervaardiging van
dunlaag- supergeleierlae gebruik word te verstaan, sal 'n oorsig van die volledige vervaardigingsproses
van 'n Josephson-patroon gegee word. Die apparaat wat gebruik is,
sal beskryf en krities ontleed word en die tekorte in ontwerp sal uitgelig word, terwyl
verbeterings aangetoon sal word. Sommige van die toerusting het voorheen bestaan
en is aangepas, byvoorbeeld die plasmalaser-neerleggingstelsel, die litografiestelsel en
die toetsfasiliteit. Nuwe ontwerpstelsels is gebou om die gehalte van ons dunlaagsupergeleiers
verder te verbeter. Dit sluit die silindriese plasma deponeer stelsel, die
Argon-ioon bron en die substraatverwarmer in.
In hierdie tesis word daar eerstens 'n oorsig gegee van die totstandkomingsproses van
'n supergeleier kwantum-interfensiemeganisme, beginnende met dunlaagneerslag van
YBCO (Yttrium, Barium en Koperoksied). Die oorsig word gevolg deur 'n stap-virstap
beskrywing van elke daaropvolgende proses wat lei tot die voltooiing van die
meganisme. Daarna word die toetsprosedure van die dunlaag en instrumente verduidelik.
Bykomende veranderinge wat aan bestaande instrumente aangebring is (ten einde
die dunfilmlae te verbeter en die toetsfasiliteit op te gradeer) word ook bespreek.
Daar sal ook verwys word na artikels wat in verskeie joernale verskyn het oor die
vernuwende aanpassings en sisteme wat in hierdie tesis verduidelik word. Ten slotte
sal die resultate van die verbeterde dunlae en strukture getoon word. Kortom: die hele
proses is ontleed en opgegradeer om 'n verbeterde apparaatvervaardigingsfasiliteit tot
gevolg te hê.
|
287 |
Phase noise measurementGrobbelaar, Johannes Jacobus 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The objective of the thesis is the development of a phase noise measuring system that makes
use of crosscorrelation and averaging to measure below the system hardware noise floor.
Various phase noise measurement techniques are considered after which the phase demodulation
method is chosen to be implemented. The full development cycle of the hardware is
discussed, as well as the post processing that is performed on the measured phase noise. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is die ontwikkeling van ’n faseruis meetstelsel wat gebruik maak
van kruiskorrelasie en vergemiddeling om onder die ruisvloer van die meetstelsel se hardeware
te meet.
Verskeie faseruis meettegnieke word ondersoek en die fase demodulasie metode word gekies
om geïmplementeer te word. Die volle ontwikkelingsiklus van die hardeware word bespreek,
sowel as die naverwerking wat toegepas is op die gemete faseruis.
|
288 |
The transputer virtual memory systemMostert, Sias January 1990 (has links)
Thesis (MIng.)--Stellenbosch University, 1990. / ENGLISH ABSTRACT: The transputer virtual memory system provide, for the transputer without memory
management primitives, a viable virtual memory system. This report evaluates
the architecture and its parameters. The basic software is also implemented a.nd
described. The disk subsystem with software and hard",,'are is also evaluated in a
single disk environment.
It is shown that the unique features of the TVM system has advantages and disadvantages
when compared to conventional virtual memory systems. One of the
advantages is that a conventional operating system with memory protection can
now also be implemented on the transputer. The main conclusion is that this is
a performance effective implementation of a virtual memory system with unique
features that should be exploited further. / AFRIKAANSE OPSOMMING: Die transputer virtuele geheue verskaf, vir 'n verwerker sander
virtuele geheue ondersteuning, 'n doeltreffende virtuele geheue
stelsel. Die verslag evalueer die argitektuur en sy parameters.
Die skyfsubstelsel met programmatuur en apparatuur word ook geevalueer
in 'n enkel skyfkoppelvlak omgewing.
Daar word bewys dat die upieke eienskappe van die TVG (transputer
virtuele geheue) voor- en nadele besit wanneer dit vElrgelyk word
met konvensionele virtuele geheue stelsels. Een van die voordele
is dat 'n konvensionele bedryfstelsel met geheue beskerming nou
op 'n transputer ge-implementeer kan word. Die hoofnadeel agv
die spesifieke argitektuur gee slegs 'n 15% degradering in
werkverrigting. Dit word egter slegs oar 'n sekere datagrootte
ervaar en kom tipies nie ter sprake wanneer daar massiewe
programme geloop word nie.
|
289 |
Implementation of a proton therapy supervisory system for iThemba LabsQhobosheane, Sehlabaka 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / Please refer to full text for abstract.
|
290 |
The conceptual design and development of novel low cost sensors for measuring the relative light emission in the pre-millisecond stages of detonating explosive chargesOlivier, Marius 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: During the course of the CSIR’s research into the characterisation of explosive sources
to devise methods of active intervention against threats, the need has arisen to research
a particular means of early identification of the threat, which is the intense light flash
during the threat detonation. For this purpose, a low cost rugged fast optical sensor
was sought, since the application thereof would imply possible destruction, especially
if integrated into an active intervention system later on.
Given the average time of about 1ms available for intervention, it is clear that the
active intervention system needs to operate within that period, hence the interest in the
characteristic light emission of detonations in the pre-millisecond time frame. It was
thought that by characterising this emitted light in terms of wavelength (temperature)
and amplitude (and maybe other unique phenomena), the size of the threat could be
determined and logic decisions derived therefrom. Needless to say, the environment in
which the detonation light emission sensor is to operate, is extremely hostile in terms
of shock, dust, flying debris, fast rise time of the explosive event, and Electro-magnetic
Interference ( EMI) caused by the detonation itself. It must be noted that the light
sensor research was driven by the outcome of research tests performed in aid of the
development of an active intervention system.
During this research the possibility of using commercially available low cost optical
detectors at room temperature in combination with cost effective narrow band pass op-
tical filters for the relative measurement of the light emission at discrete wavelengths
during explosive detonation events were investigated. In 2006, not much applicable lit-
erature could be found on this subject, hence the educated “shot-in-the-dark” approach
then, which, by a systematic approach of explosive tests and continuous evaluation up
to 2011, led to a surprisingly simple and robust low cost optical sensor. The research
commenced with a range of optical detector elements selected for their responsivity
and bandwidth in the optical spectrum of interest; the optical filtering by means of the recording of the emitted light signal during scaled down explosive tests at the Blast
Impact Survivability Research Unit (BISRU) at the University of Cape Town. These
tests were followed by full-scale tests at DBEL, and confirmed the findings at BISRU
that the light emissions at the longer wavelengths (>2 m) manifest themselves too late
for use within the intervention time frame. It was therefore decided to concentrate on
the ultra-violet (UV) to near infra-red (NIR) spectrum of the emitted light for further
full scale tests, since these discrete spectra showed the most promise for characterisa-
tion of the emitted light. During this period a robust sensor housing with detector and
filter mounts was designed for protection against blast shock and EMI.
During the following years, certain types of optical detectors that were used during
previous tests were eliminated according to results obtained, and more discrete narrow
band pass filters added in the visible to NIR spectrum. A dedicated fast instrumen-
tation amplifier (bandwidth > 1MHz and selectable gain up to 40dB) was developed
to amplify weak signals (mainly caused by the heavy load in the detector circuit to
improve rise times). However, the emission of light per wavelength in this region was
measured to be relatively strong, and actually not as fast as was anticipated. This
meant that the load resistor value of the detector element could be increased without
affecting the signal negatively (bandwidth sufficient), thus adding to the amplitude of
the signal to such a point that amplification in a 10m to 30 meter stand-off scenario
was no longer needed. This culminated in an unamplified universal detector element
being used with various narrow band pass filters up to 1 m, integrated as a very robust
analog sensor at a discrete wavelength, and facilitating the direct comparison of light
amplitude/relative intensity of the detonation at discrete spectral points.
The sensor was employed in the field at various full scale explosive tests at DBEL,
which led to the capture of a vast amount of light emitted data for different types of
explosives, at various distances from the detonation, and of varying mass. Analysis of
this data showed that the broadband light intensity of the emitted light scales to the explosive mass1/3 (as published by FJ Mostert and M Olivier in the Journal for Applied
Physics, October 2011). Further analysis also confirmed the attenuation of the emitted
light intensity by the square of the distance. Besides the aforesaid, various other key
inputs to a possible active intervention algorithm have been identified. These findings
are inputs to the determination of i.a. the detonation threat size, a vital component in
the active intervention algorithm.
The results of these experiments confirmed that the final low cost analog sensor can
measure relative light emission at discrete wavelengths from detonation of explosives in
the very early stages of development, and that the sensor has many other applications
in the detonics research fields as well. / AFRIKAANSE OPSOMMING: Gedurende die WNNR se navorsing om detonerende bronne te karakteriseer ten einde
aktiewe teenmaatreëls daar te stel, het die behoefte na vore gekom om die intense
ligflits van ’n detonasie te ondersoek en te karakteriseer. Vir hierdie doel is ’n lae
koste ligsensor benodig, synde die uiteindelike aanwending van hierdie ligsensor die
vernietiging daarvan sou beteken, aldus die lae koste vereiste.
Gegewe die kort tydsduur van die detonasie (’n paar millisekondes), is dit duidelik
dat die ligflits karakerisering voor 1ms moet geskied, en daarom moet die ligsensor
ook baie vinnig reageer om insette te lewer tot ’n aktiewe teenmaatreëlstelsel. Daar
moet op gelet word dat die ligsensor se ontwikkeling uitkomsgedrewe was deur die
navorsingstoetse om ’n aktiewe teenmaatreëlstelsel daar te stel.
Een van die insette tot so ’n aktiewe teenmaatreëlstelsel is die grootte van die
bedreiging: deur die ligflits te karakteriseer met die lae koste ligsensors t.o.v. golflengte,
ligamplitude en moontlik ander verskynsels, kan bv. die massa inset verkry word wat
nodig is vir die teenmaatreël algoritme.
Die omgewing waarin die ligsensor moet funksioneer is baie onvriendelik i.t.v. skok,
stof, vlieënde partikels en elektromagnetiese steurings, en sou daarteen beskerm moes
word.
Gedurende die navoring om so ’n ligsensor te ontwikkel (samelopend met die teen-
maatreël navorsing), is kommersiële kamertemperatuur detektors oorweeg en aange-
wend, in samewerking met nouband optiese filters. Die doel was om die ligopbrengs
per golflengte te karakteriseer m.b.t. die plofstof massa, plofstof tipe en geometrie, en
die afstand vanaf die detonasie.
Bitter min literatuur oor die ligmeting van detonasies is aanvanklik gevind, aldus is
’n basislyn daargestel en deur sistematiese toetsing, ontleding en verbetering voortgegaan met die navorsing. Dit het gelei tot ’n verrassend eenvoudige en verharde lae koste
ligsensor, wat deur meting sleutelinsette kon lewer tot die gesogte aktiewe teenmaatreël
algoritme.
Kommersiële detektors en nouband optiese filters is uitgesoek na aanleiding van
hul prys en prestasie, en waar nodig, is versterking van die seine aangebring. Verskeie
toetse met plofstof (op klein en groot skaal) is uitgevoer, waartydens ligmeting by
spesifieke golflengtes opgeneem is. Analise van hierdie data het getoon dat die langer
golflengtes (>2 m) se verskyning te laat is vir insluiting in die teenmaatreël algoritme,
en is dus geleidelik (of sistematies) uitgeskakel. Die klem het geskuif na die detonasie
liguitsetting in die UV tot naby infrarooi spektrum, wat nuwe detektors en filters tot
gevolg gehad het (uitkoms gebasseerde navorsing). In die proses is ’n instrumentasie
versterker ontwerp en gebou, vir buffering en versterking van seine hoër as 1 MHz met ’n
selekteerbare aanwins van tot 40dB. Toetse met volskaalse ladings het egter getoon dat
die liguitset besonder sterk is in die UV tot naby infrarooi spektrum, en ’n onversterkte
ligsensor is aldus op die proef gestel. Hierdie proeflopie het getoon dat die onversterkte
ligsensor besonder goed funksioneer op afstande tot en met 30m, en daar is op hierdie
model voortgebou. Die verharde onversterkte ligsensor is aangewend in verskeie verdere
volskaalse plofstof toetse, en het data gelewer t.o.v. detonasie liguitstraling by spesifieke
golflengtes vir tipes plofstof, plofstof massas, plofstof geometrie en afstande vanaf die
detonasie.
Analise van hierdie data het getoon dat breëband liguitsetting se intensiteit skaal
met die plofstof massa1=3 (gepubliseer as ’n artikel deur FJ Mostert en M Olivier in die
Journal of Applied Physics’ - Oktober 2011). Verdere analise het verskeie sleutelinsette
tot ’n aktiewe teenmaatreël algoritme geïdentifiseer.
Die uitkoms van hierdie eksperimentele navorsing het getoon dat die lae koste lig-
sensor relatiewe liguitsetting van ’n detonasie by gekose golflengtes vinnig kan meet
in die baie vroeë stadia van die detonasie. Buiten dit, het die sensor verskeie ander
nuttige aanwending in die detonasie navorsingsveld.
|
Page generated in 0.092 seconds