Design and simulation of a flux-locked-loop for use in low-frequency magnetometry systems using DC SQUIDS
| dc.contributor.advisor | Fourie, Coenrad | en_ZA |
| dc.contributor.author | Hall, Tessa | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-12-07T07:41:55Z | |
| dc.date.accessioned | 2021-12-22T14:31:50Z | |
| dc.date.available | 2021-12-07T07:41:55Z | |
| dc.date.available | 2021-12-22T14:31:50Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: his thesis presents the design of a Flux-Locked-Loop (FLL) for use in readout electronics for High Temperature Superconductor Superconducting Quantum Interference Devices (HTS SQUIDs). SQUIDs are used as extremely sensitive magnetometers in a wide range of fields, including biomedical measurements, geophysical exploration and space weather prediction. The low noise readout electronics used to control these magnetometers is prohibitively expensive and largely inaccessible to most researchers. As such, there is a need for the development of a low-cost control system that is suitable for the measurement of magnetic flux d ensities at extremely low frequencies. The proposed FLL consists of a low noise pre-amplifier, secondary amplifier w ith v oltage o ffset re moval, lo ck-in de tector, in tegrator an d fe edback ci rcuitry. In addition, it uses flux modulation a nd bias c urrent r eversal t echniques to m inimise the noise of the SQUID. The FLL configuration is designed to b e flexible, with a microcontroller used to customise the circuit to the specifications o f t heS QUID. A n umber o f p re-amplifierdesigns were evaluated to determine the most suitable implementation for this application. A full noise analysis of each design provides a useful evaluation tool for the suitability of the pre-amplifiers. The integrator and feedback system was designed to offer three sensitivity ranges, so that a wide range of magnetic flux m easurements c ould b e m ade. T he p roposed F LL d esign was simulated in LTspice XVII Circuit Simulator for a range of modelled magnetic flux i nputs. The simulation results are very promising with the FLL accurately tracking the modelled magnetic flux input for a range of frequencies and magnetic flux d ensities. These simulation results suggest that, with a few improvements, the proposed FLL could be successfully implemented in a physical system. As a result, this thesis constitutes a promising step forward in reaching the goal of creating accessible low-cost SQUID readout electronics for low frequency magnetic flux density measurements | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: In hierdie tesis word die ontwerp van ’n vloedsluitlus (FLL) vir gebruik in uitleeselektronika vir Ho ̈e-Temperatuur Supergeleier Kwantum-Inteferensie Toestelle (HTS SQUIDs) aangebied. SQUIDs word gebruik as uiters sensitiewe magnetometers op ’n wye verskeidenheid gebiede, insluitend biomediese metings, geofisiese verkenning en die meet en voorspelling van ruimteweer. Die gespesialiseerde laeruis uitleeselektronika wat gebruik word om hierdie magnetometers te beheer is baie duur en dus vir die meeste navorsers grootliks ontoeganklik. As sodanig is daar ’n behoefte aan die ontwikkeling van ’n goedkoop beheerstelsel wat geskik is vir die meting van magnetiese vloeddigthede by uiters lae frekwensies. Die voorgestelde FLL bestaan uit ’n laeruis-voorversterker, ’n sekondˆere versterker wat die afsetspanning verwyder, ’n sluitde- tektor, ’n integrator en ’n terugvoerstroombaan. Daarbenewens gebruik dit vloedmodulasie en voorspanningsomkeertegnieke om die ruis van die SQUID tot ’n minimum te beperk. Die buigsame FLL-opset gebruik ’n mikrobeheerder om die stroombaan aan te pas by die spesi- fikasies van die SQUID. ’n Aantal voorversterkerontwerpe is ge ̈evalueer om die mees geskikte implementering vir hierdie toepassing te bepaal. ’n Volledige ruisontleding van elke ontwerp bied ’n nuttige evalueringsinstrument vir die geskiktheid van die voorversterkers. Die integrator en terugvoerstelsel is ontwerp om drie sensitiwiteitsreekse aan te bied, sodat ’n wye reeks magnetiese vloedmetings gedoen kan word. Die voorgestelde FLL-ontwerp is gesimuleer met die LTspice elektriese stroombaansimulator vir ’n reeks gemodelleerde magnetiese vloedintrees. Die simulasie-resultate is baie belowend, aangesien die FLL die gemodelleerde magnetiese vloedinvoer akkuraat volg vir ’n reeks frekwensies en magnetiese vloeddigthede. Hierdie simulasie-resultate dui daarop dat die voorgestelde FLL met ’n paar verbeterings suksesvol in ’n fisiese stelsel ge ̈ımplementeer kan word. As gevolg hiervan vorm hierdie tesis ’n belowende stap vorentoe om die doelwit te bereik om toeganklike goedkoop SQUID-uitleeselektronika vir laefrekwensie magnetiese vloeddigtheidmetings te skep | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.format.extent | 135 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/123964 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Magnetometry systems | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | SQUID devices | en_ZA |
| dc.subject | Superconducting Quantum Interference Devices | en_ZA |
| dc.subject | Weather prediction | en_ZA |
| dc.subject | National Space Agency | en_ZA |
| dc.subject | Flux-Locked-Loop | en_ZA |
| dc.subject | Magnetic flux | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Design and simulation of a flux-locked-loop for use in low-frequency magnetometry systems using DC SQUIDS | en_ZA |
| dc.type | Thesis | en_ZA |