Sensitivity improvement of GMI magnetic and pressure transducers for biomedical measurements

Abstract

This work presents an experimental study aiming the sensitivity optimization of Giant Magnetoimpedance (GMI) sensors, by means of properly choosing the values of their conditioning parameters. The optimized GMI sensors, together with the development of improved transduction electronic circuits, can lead to the sensitivity enhancement of GMI biomedical, pressure and magnetic transducer prototypes, previously developed by the research group at LaBioMet, PUC-Rio. Those prototypes are, respectively, aimed at the measurement of arterial pulse waves and the localization of magnetic foreign bodies inserted in the human body. Thus, the experimental characterization of GMI ribbon-shaped samples (Co 70 Fe 5 Si 15 B 10 ) was performed, as a function of the external magnetic field, including the experimental evaluation of the asymmetric GMI effect (AGMI). The parameters that affect the behavior of the GMI samples were experimentally analyzed, such as the DC level (0 mA to 100 mA) and frequency (100 kHz to 10 MHz) of the excitation current, as well as the samples length (1 cm, 3 cm, 5 cm and 15 cm). The conditioning parameters, experimentally identified, that optimize the GMI samples sensitivity lead to a maximum specific sensitivity of 0.84(8400 Ω ·T -1 ·cm -1 ). A new electronic circuit was developed for conditioning and reading of the GMI samples, which directly contributed to the performance enhancement of both transducers. The electronic circuits developed were evaluated supposing the operation of the GMI samples in their most sensitive region. Comparing to previously developed prototypes, the optimum sensitivity achieved for the new configuration of the GMI magnetic transducer increased about 9 times (from 0.12 mV/nT to 1.08 mV/nT), and the sensitivity of the modified pressure transducer increased approximately 7 times (from 1 mV/Pa to 7 mV/Pa). Keywords

Development of a fast and reliable system for the automatic characterization of Giant magnetoimpedance samples

“…In spite of the GMI effect being a recent discovery, GMI magnetometers have already been developed for various applications, among which stand out: presence detectors [3], industrial process control [4], space research and aerospace applications [1,5], navigation systems [6], high-density memories and HDs [7], traffic control [8], cracks detection in materials [9], and biological and biomedical applications [10][11][12][13][14][15][16].…”

Demanda Por Calibração De Instrumentos De Medição De Grandezas Magnéticas No Brasil

“…Os resultados obtidos até o momento (Cavalcanti et al, 2008;Louzada et al, 2008 ;Silva et al, 2010 ;Costa Silva et al, 2011;Silva et al, 2011;Silva et al, 2013) Figura 10-Estrutura da rastreabilidade metrológica com a disposição dos organismos participantes da cadeia de rastreabilidade metrológica e disseminação das unidades do SI.…”

Proposta De Dispositivo Biomédico Multisensor Portátil Para Localização De Corpos Estranhos Ferromagnéticos

“…Já foram realizados ensaios visando novos tipos de configurações geométricas [9] e métodos para otimizar a sensibilidade dos sensores [10]. As técnicas de localização de corpos estranhos, por meio desses magnetômetros e algoritmos computacionais, ainda estão em desenvolvimento e sendo aperfeiçoadas, conforme novas pesquisas são realizadas na área.…”