Digital Signal Processing by Virtual Instrumentation of a MEMS Magnetic Field Sensor for Biomedical Applications (original) (raw)
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2013
We present a signal processing system with virtual instrumentation of a MEMS sensor to detect magnetic flux density for biomedical applications. This system consists of a magnetic field sensor, electronic components implemented on a printed circuit board (PCB), a data acquisition (DAQ) card, and a virtual instrument. It allows the development of a semi-portable prototype with the capacity to filter small electromagnetic interference signals through digital signal processing. The virtual instrument includes an algorithm to implement different configurations of infinite impulse response (IIR) filters. The PCB
Respiratory Magnetogram Detected with a MEMS Device
Magnetic fields generated by the brain or the heart are very useful in clinical diagnostics. Therefore, magnetic signals produced by other organs are also of considerable interest. Here we show first evidence that thoracic muscles can produce a strong magnetic flux density during respiratory activity, that we name respiratory magnetogram. We used a small magnetometer based on microelectromechanical systems (MEMS), which was positioned inside the open thoracic cage of anaesthetized and ventilated rats. With this new MEMS sensor of about 20 nT resolution, we recorded a strong and rhythmic respiratory magnetogram of about 600 nT.
Review of Scientific Instruments, 1998
We have recorded the magnetic signal generated by the human cardiac muscle with the help of a very sensitive flux-gate sensor. First, we have verified the feasibility of such detection inside a magnetically shielded room, then repeated this same experiment within our laboratory and in a low shielded environment. Results have shown the easy operation of a flux-gate sensor for this purpose and the efficiency of fast numerical processing in a low shielded environment. This leads in both cases to a voltage signal-to-noise ratio of about 5 within a 100 Hz bandwidth, which corresponds to the actual limit of the flux-gate probe.
Quantitative Evaluation for Magnetoelectric Sensor Systems in Biomagnetic Diagnostics
Sensors, 2022
Dedicated research is currently being conducted on novel thin film magnetoelectric (ME) sensor concepts for medical applications. These concepts enable a contactless magnetic signal acquisition in the presence of large interference fields such as the magnetic field of the Earth and are operational at room temperature. As more and more different ME sensor concepts are accessible to medical applications, the need for comparative quality metrics significantly arises. For a medical application, both the specification of the sensor itself and the specification of the readout scheme must be considered. Therefore, from a medical user’s perspective, a system consideration is better suited to specific quantitative measures that consider the sensor readout scheme as well. The corresponding sensor system evaluation should be performed in reproducible measurement conditions (e.g., magnetically, electrically and acoustically shielded environment). Within this contribution, an ME sensor system ev...
Biopotential amplifier for simultaneous operation with biomagnetic instruments
Medical & Biological Engineering & Computing, 1997
AbstractwA multichannel biopotential amplifier for simultaneous use with biomagnetic measurements in a magnetically shielded room is designed and evaluated. Particular care is taken to make the amplifier electromagnetically compatible with the biomagnetic instruments over the whole frequency spectrum, from DC to RF. The electromagnetically quiet environment allows the use of high electrode impedances; the preamplifier has been designed accordingly. Special care is taken to analyse the coupling mechanisms of mains interference to the amplifier. Over 170 simultaneous electric and magnetic recordings have been performed using the system in a hospital environment.
High-Precision Biomagnetic Measurement System Based on Tunnel Magneto-Resistive Effect
2020 27th IEEE International Conference on Electronics, Circuits and Systems (ICECS)
This paper presents a novel low-noise and highprecision readout circuit for tunnelling magnetoresistive (TMR) array to evaluate the suitability of biomagnetic measurement platform for detection of weak biomagnetic fields. We propose a three operational-amplifier architecture with a high input impedance and an adjustable gain for the fabricated TMR sensor that is highly miniaturized and can be operated at room temperature. The proposed system was designed using standard 0.18 µm CMOS technology and achieved a good performance with regard to gain, linearity, power consumption, and noise by employing a chopper stabilization technique and common mode feedback. The gain can reach 80 dB through adjusting two 5-bit programmable resistors and the input-referred noise voltage only has 44.6 nV/√Hz with 10 nA input bias over a wide range of frequency. Moreover, the whole readout dissipates 58 µW of power with a 1.8 V supply voltage. Benefiting from the CMOS compatibility of the TMR sensor, it offers monolithic integration directly on a silicon substrate as a TMR-on-chip sensing system. This will enable a new scientific and engineering paradigm to revitalize the biomagnetism field as an alternative way to understand the underlying mechanism of the human body.
A Novel Magnetic Respiratory Sensor for Human Healthcare
Applied Sciences
Breathing is vital to life. Therefore, the real-time monitoring of a patient′s breathing pattern is crucial to respiratory rehabilitation therapies, such as magnetic resonance exams for respiratory-triggered imaging, chronic pulmonary disease treatment, and synchronized functional electrical stimulation. While numerous respiratory devices have been developed, they are often in direct contact with a patient, which can yield limited data. In this study, we developed a novel, non-invasive, and contactless magnetic sensing platform that can precisely monitor a patient′s breathing, movement, or sleep patterns, thus providing efficient monitoring at a clinic or home. A magneto-LC resonance (MLCR) sensor converts the magnetic oscillations generated by a patient′s breathing into an impedance spectrum, which allows for a deep analysis of one′s breath variation to identify respiratory-related diseases like COVID-19. Owing to its ultrahigh sensitivity, the MLCR sensor yields a distinct breathi...
Magnetic field exposure and behavioral monitoring system
Bioelectromagnetics, 2001
To maximize the availability and usefulness of a small magnetic ®eld exposure laboratory, we designed a magnetic ®eld exposure system that has been used to test human subjects, caged or con®ned animals, and cell cultures. The magnetic ®eld exposure system consists of three orthogonal pairs of coils 2 m square  1 m separation, 1.751 m  0.875 m separation, and 1.5 m  0.75 m separation. Each coil consisted of ten turns of insulated 8 gauge stranded copper conductor. Each of the pairs were driven by a constant-current ampli®er via digital to analog (D/A) converter. A 9 pole zero-gain active Bessel low-pass ®lter (1 kHz corner frequency) before the ampli®er input attenuated the expected high frequencies generated by the D/A conversion. The magnetic ®eld was monitored with a 3D¯uxgate magnetometer (0±3 kHz, AE 1 mT) through an analog to digital converter. Behavioral monitoring utilized two monochrome video cameras (viewing the coil center vertically and horizontally), both of which could be video recorded and real-time digitally Moving Picture Experts Group (MPEG) encoded to CD-ROM. Human postural sway (standing balance) was monitored with a 3D forceplate mounted on the¯oor, connected to an analog to digital converter. Lighting was provided by 12 offset overhead dimmable¯uorescent track lights and monitored using a digitally connected spectroradiometer. The dc resistance, inductance of each coil pair connected in series were 1.5 m coil (0.27 O, 1.2 mH), 1.75 m coil (0.32 O, 1.4 mH), and 2 m coil (0.38 O, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at AE 463 mT, 1 kHz at AE 232 mT, 150 ms rise time from À200 mT pk to 200 mT pk (square wave) and is limited by the maximum voltage (AE 146 V) of the ampli®er (Bessel ®lter bypassed). Bioelectromagnetics 22:401±407, 2001.
A portable diagnostic device for cardiac magnetic field mapping
In this paper we present a portable magnetocardiography device. The focus of this development was delivering a rapid assessment of chest pain in an emergency department. The aim was therefore to produce an inexpensive device that could be rapidly deployed in a noisy unshielded ward environment. We found that induction coil magnetometers with a coil design optimised for magnetic field mapping possess sufficient sensitivity ( - / 104 fT Hz 1 2 noise floor at 10 Hz) and response ( m - 813 fT V 1 at 10 Hz)for cycle averaged magnetocardiography and are able to measure depolarisation signals in an unshielded environment. We were unable to observe repolarisation signals to a reasonable fidelity. We present the design of the induction coil sensor array and signal processing routine along with data demonstrating performance in a hospital environment.
Biomagnetic systems for clinical use
2000
We present two multichannel systems based on a superconducting quantum interference device (SQUID) for biomagnetic measurements, installed at the University of Chieti. Both systems have been designed for clinical and routine use and have been developed owing to an international cooperation. The main issues in the instrument implementation were ®eld sensitivity and spatial resolution, as well as¯exibility and stability during operation. The ®rst system is a planar system and is devised for magnetocardiographic measurements. This system is composed of 74 dc SQUID integrated magnetometers contained in a low-noise dewar: 55 sensors are measurement channels and 21 are placed far from the subject and are used as reference channels to create software gradiometers. The second system is a helmet system and consists of 165 dc SQUID integrated magnetometers to perform magnetoencephalographic recordings; 153 channels are distributed over a surface covering the whole scalp and 12 channels are used as references. The ®eld noise of the SQUID magnetometers is about 5 fT Hz ¡1=2 . Each system is placed in a magnetically shielded room for eddy current shielding and magnetic shielding. The magnetic ®eld is recorded with sampling frequencies up to 10 kHz. The analogue-to-digital converted data are processed on line by means of an array of digital signal processors, allowing bandpass ®ltering, decimation and noise compensation.