Implementation of MEMS Accelerometer for Velocity-based Seismic Sensor

Micro Electro Mechanical System (MEMS) accelerometer is commonly used as acceleration-based vibration sensor. The MEMS accelerometer is small device, simple in the implementation design, and relatively inexpensive. But in some fields of application, due to low frequency operation and also small magnitude of the measured signal, for example in seismology, velocity-based vibration sensor is usually more desirable than acceleration-based sensor. In this research, a velocity-based vibration sensor has been developed using MEMS Accelerometer device e.g. MMA7361L. The acceleration-based vibration signal from the MMA7361L is converted into a velocity-based vibration signal by using an integrator circuit module. This module is assembled by using a band-pass filter and an integral-amplifier. The laboratory test shows that the developed sensor system could detect both low and high-frequency vibration signals in velocity-based with good result. The sensor system has a frequency range of 0.02Hz to 148Hz. It is wider frequency than the geophone (seismic sensor), thus the velocity-based MEMS sensor system has capability for geophone replacement

Implementation of MEMS Accelerometer for Velocity-based Seismic Sensor

Micro Electro Mechanical System (MEMS) accelerometer is commonly used as acceleration-based vibration sensor. The MEMS accelerometer is small device, simple in the implementation design, and relatively inexpensive. But in some fields of application, due to low frequency operation and also small magnitude of the measured signal, for example in seismology, velocity-based vibration sensor is usually more desirable than acceleration-based sensor. In this research, a velocity-based vibration sensor has been developed using MEMS Accelerometer device e.g. MMA7361L. The acceleration-based vibration signal from the MMA7361L is converted into a velocity-based vibration signal by using an integrator circuit module. This module is assembled by using a band-pass filter and an integral- amplifier. The laboratory test shows that the developed sensor system could detect both low and high-frequency vibration signals in velocity-based with good result. The sensor system has a frequency range of 0.02Hz to 148Hz. It is wider frequency than the geophone (seismic sensor), thus the velocity- based MEMS sensor system has capability for geophone replacement

UV-LIGA micro-fabrication of inertia type electrostatic transducers and their application

This dissertation discusses the design, working principles, static & dynamic analysis and simulation, mechanics of material, applied MEMS technology, micro-fabrication, and experimental testing of two types of micro-transducers: micro-power relay and micro-accelerometer. Several possible design concepts were proposed, and the advantages and disadvantages of electrostatic working principles were also discussed. Transducers presented in this research used electrostatic force as a driving force in the micro-relay and capacitance as a sensing parameter in the micro-accelerometer. There was an analogy between the micro-relay and the micro-accelerometer in their theoretical approach and fabrication processes. The proposed micro-transducers (micro-relay and micro-accelerometer) were fabricated using UV lithograph of SU-8 & SPR and UV-LIGA process. The advantages and disadvantages of these processes were discussed. The micro-relays fabricated by UV-LIGA technology had the following advantages compared with other reported relays: fast switching speed, high power capacity, high off-resistance, lower on-resistance, low power consumption, and low heat generation. The polymer-based micro-accelerometers were designed and fabricated. Instead of applying SU-8 only as a photo resist, cured SU-8 was used as the primary structural material in fabricating the micro-accelerometers. The great flexibility in size and aspect ratio of cured SU-8 made it feasible to produce highly sensitive accelerometers. The prototype micro-relays and micro-accelerometers were tested for the dynamic characteristics and power capacity. The experimental results in micro-relays had confirmed that reasonably large current capacity and fast response speed was able to be achieved using electromagnetic actuation and the multilayer UV-LIGA fabrication process

Smart polymeric temperature sensors – for biological systems

The damaged brain is vulnerable to increase in brain temperature after a severe head injury. Continuous monitoring of intracranial temperature depicts functionality essential to the treatment of brain injury Many innovations have been made in the biomedical industry relying on electronic implants in treating condition such as traumatic brain injury (TBI) or other cerebral diseases. Hence, a methodical and reliable way to measure the temperature is crucial to assess the patient’s situation. In this investigation, an analysis of various approaches to detect the change in the temperature due to resistance, current-voltage characteristics with respect to time has been evaluated. Also, studies describing various materials used in sensors, their working principles and the results anticipated in these discrete procedures are presented. These smart temperature sensors have provided the accuracy and the stability compared to earlier methods used to detect the change in brain temperature since temperature is one of the most important variables in brain monitoring

A three-axis accelerometer for measuring heart wall motion

This thesis presents the work carried out in the design, simulation, fabrication and testing of miniaturised three-axis accelerometers. The work was carried out at the Faculty of Science and Engineering at Vestfold University College (Tønsberg, Norway), the MIcroSystems Engineering Centre (MISEC) at Heriot-Watt University and in collaboration with the Interventional Centre at Rikshospitalet University Hospital (Oslo, Norway). The accelerometers presented in this thesis were produced to be stitched to the surface of human hearts. In doing so they are used to measure the heart wall motion of patients that have just undergone heart bypass surgery. Results from studies carried out are presented and prove the concept of using such sensors for the detection of problems that can lead to the failure of heart bypasses. These studies were made possible using commercially available MEMS (MicroElectroMechanical Systems) three-axis accelerometers. However, the overall size of these sensors does not meet the requirements deemed necessary by the medical team (2(W) 2(H) 5(L) mm3) and fabrication activities were necessary to produce custom-made sensors. Design verification and performance modelling were carried out using Finite Element Analysis (FEA) and these results are presented alongside relevant analytical calculations. For fabrication, accelerometer designs were submitted to three foundry processes during the course of the work. The designs utilise the piezoresistive effect for the acceleration sensing and fabrication was carried out by bulk micromachining. Results of the characterisaton of the sensors are presente

Advances in High-Resolution Microscale Impedance Sensors

Sensors based on impedance transduction have been well consolidated in the industry for decades. Today, the downscaling of the size of sensing elements to micrometric and submicrometric dimensions is enabled by the diffusion of lithographic processes and fostered by the convergence of complementary disciplines such as microelectronics, photonics, biology, electrochemistry, and material science, all focusing on energy and information manipulation at the micro- and nanoscale. Although such a miniaturization trend is pivotal in supporting the pervasiveness of sensors (in the context of mass deployment paradigms such as smart city, home and body monitoring networks, and Internet of Things), it also presents new challenges for the detection electronics, reaching the zeptoFarad domain. In this tutorial review, a selection of examples is illustrated with the purpose of distilling key indications and guidelines for the design of high-resolution impedance readout circuits and sensors. The applications span from biological cells to inertial and ultrasonic MEMS sensors, environmental monitoring, and integrated photonics

Fungsionalisasi Mems Accelerometer Sebagai Sensor Seismik

Sensor getaran merupakan komponen penting dalam bidang seismologi, seperti pemantauan bencana alam dan eksplorasi sumber daya alam. Saat ini sensor getaran yang sering digunakan adalah sensor Geofon berbasis elektromagnetik. Namun sensor tersebut memiliki beberapa kelemahan yaitu, memiliki ukuran yang besar, harga yang cukup mahal serta terdapat kesulitan dalam proses perawatan. Berdasarkan kelemahan tersebut saat ini muncul teknologi alternatif dalam pengembangan sensor getaran yaitu, sensor MEMS Accelerometer yang bekerja berdasarkan prinsip kapasitansi. MEMS memiliki beberapa kelebihan sebagai sensor getaran, yaitu berbentuk chip IC dengan ukuran yang sangat kecil, memiliki sensitivitas 800mV/[email protected], dan memiliki tiga komponen kerja (x, y, dan z). Pada penelitian ini telah dikembangkan sensor MEMS Accelerometer tipe MMA7361L sebagai sensor seismik berbasis percepatan dan kecepatan. Untuk pengembangan sensor MEMS sebagai kecepatan diperlukan modifikasi menggunakan rangkaian integrator untuk merubah sinyal percepatan menjadi sinyal kecepatan. Berdasarkan hasil penelitian MEMS percepatan dapat merespon getaran yang memiliki frekuensi tinggi serta amplitudo yang tinggi pula dengan frekuensi diatas 30Hz. Sedangkan untuk MEMS kecepatan cut-off rendah mampu merespon getaran dengan frekuensi dibawah 1Hz

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc