Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications

Automotive Inductive Position Sensor

Inductive angular position sensors (IAPS) are widely used for high accuracy and low cost angular position sensing in harsh automotive environments, such as suspension height sensor and throttle body position sensor. These sensors ensure high resolution and long lifetime due to their contactless sensing mode and their simple structure. Furthermore, they are suitable for wider application areas. For instance, they can be miniaturized to fit into a compact packaging space, or be adopted to measure the relative angle of multiple rotating targets for the purposes of torque sensing. In this work, a detailed SIMULINK model of an IAPS is first proposed in order to study and characterize the sensor performance. The model is validated by finite element analysis and circuit simulation, which provides a powerful design tool for sensor performance analysis. The sensor error introduced by geometry imperfection is thoroughly investigated for two-phase and three-phase configurations, and a corresponding correction method to improve the accuracy is proposed. A design optimization method based on the response surface methodology is also developed and used in the sensor development. Three types of sensors are developed to demonstrate the inductive sensor technology. The first type is the miniaturized inductive sensor. To compensate for the weak signal strength and the reduced quality (Q) factor due to the scaling down effect, a resonant rotor is developed for this type of sensor. This sensor is fabricated by using the electrodeposition technique. The prototype shows an 8mm diameter sensor can function well at 1.5mm air gap. The second type is a steering torque sensor, which is designed to detect the relative torsional angle of a rotating torsional shaft. It demonstrates the mutual coupling of multiple inductive sensors. By selecting a proper layout and compensation algorithm, the torque sensor can achieve 0.1 degree accuracy. The third type is a passive inductive sensor, which is designed to reduce power consumption and electromagnetic emissions. The realization and excellent performance of these three types of sensors have shown the robustness of the inductive sensor technology and its potential applications. The research conducted in this dissertation is expected to improve understanding of the performance analysis of IAPS and provide useful guidelines for the design and performance optimization of inductive sensors

Performance degradation effect countermeasures in residence times difference (RTD) fluxgate magnetic sensors

This paper aims to explore the detection defect of residence times difference (RTD) fluxgate working in low-power mode and present the countermeasures for sensor resolution improvement and linearity enhancement. The main defects are amplitude and symmetry changes induced in the output spikes of fluxgate probe due to the magnetic field. These defects lead to thresholds deviation and asymmetry, then cause severe performance degradation especially on detection resolution and linearity according to the RTD theory. To overcome such effects, the optimized RTD method based on voltage extraction and feedback technology is proposed to implement magnetic field compensation and achieve a zero-field running regime of the RTD fluxgate. In this regard, the sensor linearity is improved by a factor of 38, and the resolution degradation effect is suppressed more than 6 times, verified by the laboratory experiments. The optimized detection method proposed in this paper demonstrated a great potential to achieve lower power consumption and will make the RTD fluxgate more promising technology among bio-magnetic applications

Design, manufacture and test of a magnetic encoder

An new eddy current based magnetic position encoder structure is proposed and studied in this thesis. The encoder is composed of one read head and one scale with metal plates placed periodically on a substrate. The read head contains one emitter and two receiver pairs which are all rectangular planar coils. The electromagnetic coupling between the emitter and receivers were affected by the relative position of the scale. A system level analytical model of the proposed encoder structure has been derived, from which three different encoder signals forms were generated. An amplification and synchronous demodulation circuit has been designed and fabricated. The circuit board was used successfully to process the encoder output signals in the measurement. Four PCB encoder prototypes were fabricated. These encoder structures were studied using the ANSYS MaxwellTM software package. The simulated and measured results were compared. The best accuracy performance of the PCB encoder is -15 μm to 15 μm from the simulation results and -35 μm to 25 μm from the corresponding measurement. An alternative manufacturing process of the magnetic encoder based on multilayer Low Temperature Co-fired Ceramic (LTCC) technology has also been presented. The fabrication process of the LTCC encoder and equipment used were described. Two different methods were used to characterise the LTCC encoder with good agreement between all approaches attempted. The best accuracy performance of the LTCC encoder was -30 μm to 25 μm and after lookup table correction the improved accuracy ranged from -10 μm to 10 μm

Magnetic DNA detection sensor for point-of-care diagnostics

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonThis thesis focuses on inductive base sensor design at MHz range frequency. The background theory, design, experiments and results for a new magnetic particles sensor is presented. A new magnetic sensor based on a planar coil was investigated for DNA pathogen detection. Change in inductance of the planar coil due to the presence of magnetic particles with varying mass was measured. The experimental set-up consisted of different sized planar coil with associated electronics for inductance measurements. The best sensor performance was accomplished using two different inductors while oscillating at frequencies 2.4MHz using 9.5μH inductor and 7.2MHz with 85μH inductor. The sensor has very large signal to noise ratio (580×103), while the average amount of frequency drift was 0.58. This sensor was tested with various types of magnetic particles. In addition, iron-oxide nanoparticles were synthesized through water in oil microemulsion method and with an average size of 25nm. The best sensitivity achieved for detection of 50μg iron-oxide particles was with the bead size of 10nm. 81Hz frequency shift was attained in regard to that amount of particles. This research shows that increasing the resonance frequency to 7.2MHz can cause the larger output signal difference (frequency shift) in the presence of magnetic particles; however, the sensor stability is the most important factor for determining the detection resolution and sensitivity. The sensitivity is better if the sensor can detect smaller amount of magnetic sample. The results of this research demonstrate that while the sample consists of smaller size particles, the sensor can detect the lower amount of sample. This is due to the heating effect of nanoparticles. On the other hand the sample distance from the sensor has a major impact on the sensitivity too; the shorter the distance, the higher the sensitivity. This technique can potentially be extended to detect several different types of bacterial pathogens and can be modified for multiplex quantitative detection. This sensing technique will be incorporated into a handheld, disposable microfluidic chip for point-of-care diagnostics for sexually transmitted diseases. Key words: Point of care diagnostics, Magnetic particle Detection, Molecular detection, Inductive sensin

Wireless mains sensor for monitoring domestic energy consumption

Abstract. Past studies have shown that awareness of energy consumption can lead to reduction in electricity usage and that real-time, per-appliance data on electricity consumption would provide greater utility and actionable information. Yet, the customers of today’s utility companies typically have to be content with data that is aggregated, delayed and difficult to access. Comprehensive real-time data would also aid in optimizing energy consumption with respect to dynamic pricing and avoiding peak consumption periods. The objective of this thesis was to design and manufacture a wireless sensor for continuous and real-time metering of the energy consumption of a household in the UBI-AMI system version 2. The resulting Mains sensor reads the total energy consumption from the kilowatt hour meter using either a galvanic or an optical connection. The individual loads of the fuses in the circuit breaker panel are measured with Hall sensors. An 8-bit microcontroller collects analog measurements, conducts 10-bit ADC and transmits the resulting digital data to the UBI-AMI system using a commercial 6LoWPAN radio module and the CoAP protocol. The data enables the differentiation of the energy consumption of integrated and built-in elements such as floor heating and sauna from the total energy consumption of the household. The Mains sensor was tested with a demonstrator that comprised of a fuse board, a kilowatt hour meter and sockets for connecting loads. The Mains sensor was found to be flawless in reading the total energy consumption from the kilowatt hour meter using a galvanic connection. The sensor was able to read 84% of fast pulses and showed 4% surplus with slow pulses if the optical connection was used. The Hall sensors had a maximum average error of 0.47% with an active power, in comparison to a commercial energy meter. These results show that the Mains sensor provides sufficiently accurate and reliable information for improving the awareness of energy consumption of a household.Langaton sähköpäätaulusensori kotitalouden energiankulutuksen seuraamiseen. Tiivistelmä. Tutkimusten mukaan tietoisuus energiankulutuksesta voi johtaa sähkön käytön vähenemiseen, ja että tosiaikainen, laitekohtainen kulutustieto olisi hyödyllisempää. Silti nykyisin sähköyhtiöiden asiakkaiden täytyy tyypillisesti tyytyä kulutustietoihin, jotka on kerätty kokonaiskulutuksesta, ovat käytettävissä viiveellä, ja joihin on vaikea päästä käsiksi. Kattava tosiaikainen informaatio myös auttaisi huippukulutuskausien välttämisessä ja energiankulutuksen optimoinnissa dynaamisen hinnoittelun suhteen. Tämän diplomityön tavoitteena oli suunnitella ja valmistaa langaton sensori kotitalouden energiankulutuksen jatkuvaan ja tosiaikaiseen mittaukseen osana UBI-AMI-järjestelmän versiota 2. Syntynyt sähköpäätaulusensori lukee kokonaisenergiankulutuksen kilowattituntimittarista joko galvaanista tai optista yhteyttä käyttäen. Yksittäiset ryhmäkohtaiset kuormat mitataan sulaketaulusta Hallin antureilla. 8-bittinen mikrokontrolleri kerää analogiset mittaukset ja muuntaa ne digitaaliseksi dataksi, joka lähetetään UBI-AMI-järjestelmälle käyttäen kaupallista 6LoWPAN-radiomoduulia ja CoAP-protokollaa. Mittausdata mahdollistaa integroitujen ja kiinteästi asennettujen sähkölaitteiden, esimerkiksi lattialämmityksen ja saunan, energiankulutuksen eriyttämisen kotitalouden kokonaiskulutuksesta. Sähköpäätaulusensorin toiminta arvioitiin testilaitteistolla, joka koostui sulaketaulusta, kilowattituntimittarista ja pistorasioista kuormien liittämistä varten. Sähköpäätaulusensorin havaittiin lukevan kokonaisenergiankulutuksen kilowattituntimittarista virheettömästi galvaanista yhteyttä käyttäen. Optista yhteyttä käytettäessä sensori kykeni lukemaan 84 % nopeista pulsseista ja hitaat pulssit saivat sensorin mittaamaan käytetyn energian 4% todellista suuremmaksi. Hallin antureilla suurin keskimääräinen virhe kaupalliseen mittariin verrattuna oli 0,47 % pätötehollisella kuormalla. Tulosten perusteella sähköpäätaulusensori antaa riittävän tarkkaa ja luotettavaa tietoa energiankulutuksesta ja sitä voidaan käyttää energiankulutuksen tietoisuuden lisäämiseen kotitalouksissa

Phase Noise Analyses and Measurements in the Hybrid Memristor-CMOS Phase-Locked Loop Design and Devices Beyond Bulk CMOS

Phase-locked loop (PLLs) has been widely used in analog or mixed-signal integrated circuits. Since there is an increasing market for low noise and high speed devices, PLLs are being employed in communications. In this dissertation, we investigated phase noise, tuning range, jitter, and power performances in different architectures of PLL designs. More energy efficient devices such as memristor, graphene, transition metal di-chalcogenide (TMDC) materials and their respective transistors are introduced in the design phase-locked loop. Subsequently, we modeled phase noise of a CMOS phase-locked loop from the superposition of noises from its building blocks which comprises of a voltage-controlled oscillator, loop filter, frequency divider, phase-frequency detector, and the auxiliary input reference clock. Similarly, a linear time-invariant model that has additive noise sources in frequency domain is used to analyze the phase noise. The modeled phase noise results are further compared with the corresponding phase-locked loop designs in different n-well CMOS processes. With the scaling of CMOS technology and the increase of the electrical field, the problem of short channel effects (SCE) has become dominant, which causes decay in subthreshold slope (SS) and positive and negative shifts in the threshold voltages of nMOS and pMOS transistors, respectively. Various devices are proposed to continue extending Moore\u27s law and the roadmap in semiconductor industry. We employed tunnel field effect transistor owing to its better performance in terms of SS, leakage current, power consumption etc. Applying an appropriate bias voltage to the gate-source region of TFET causes the valence band to align with the conduction band and injecting the charge carriers. Similarly, under reverse bias, the two bands are misaligned and there is no injection of carriers. We implemented graphene TFET and MoS2 in PLL design and the results show improvements in phase noise, jitter, tuning range, and frequency of operation. In addition, the power consumption is greatly reduced due to the low supply voltage of tunnel field effect transistor

Piezoelectric Transformer and Hall-Effect Based Sensing and Disturbance Monitoring Methodology for High-Voltage Power Supply Lines

Advancements in relaying algorithms have led to an accurate and robust protection system widely used in power distribution. However, in low power sections of relaying systems, standard voltage and current measurement techniques are still used. These techniques have disadvantages like higher cost, size, electromagnetic interference, resistive losses and measurement errors and hence provide a number of opportunities for improvement and integration. We present a novel microsystem methodology to sense low-power voltage and current signals and detect disturbances in high-voltage power distribution lines. The system employs dual sensor architecture that consists of a piezoelectric transformer in combination with Hall-effect sensor, used to detect the disturbances whose harmonics are in the kHz frequency range. Our numerical analysis is based on three-dimensional finite element models of the piezoelectric transformer (PT) and the principle of Hall-effect based “Integrated Magnetic Concentrator (IMC)” sensor. This model is verified by using experimental data recorded in the resonant frequency and low frequency regions of operation of PT for voltage sensing. Actual measurements with the commercial IMC sensor too validate the modelling results. These results describe a characteristic low frequency behaviour of rectangular piezoelectric transformer, which enables it to withstand voltages as high as 150V. In the frequency range of 10Hz to 250Hz, the PT steps down 10-150V input with a linearity of ±1%. The recorded group delay data shows that propagation delay through PT reduces to few microseconds above 1kHz input signal frequency. Similarly, the non-intrusive current sensor detects current with a response time of 8μs and converts the current into corresponding output voltage. These properties, in addition to frequency spectrum of voltage and current input signals, have been used to develop a signal processing and fault detection system for two real-time cases of faults to produce a 6-bit decision logic capable of detecting various types of line disturbances in less than 3ms of delay