Abstract: The detection of bio-magnetic activities enables non-contact and non-invasive evaluation of electrical activity in living organisms. In this paper a practical method to achieve bio-magnetic field detection in non-magnetically shielded environment at the RT in introduced. This method is based on Giant Magneto-Impedance (GMI) Effect in amorphous wire. At first, bio-magnetic fields and the principal of GMI effect are reviewed. After that off-diagonal GMI effect measurement experiment is carried out to obtain the circuit design requirement. The experimental result is formed that, if the sensitivity of GMI sensors reach to 10 pico-Tesla (pT) level, the gain of amplifier circuit should be more than 10 thousand times. It is almost impossible to obtain so much gain by only one order amplifier circuit, so the circuit was designed using several orders for sake of a stable and high gain (A>=100,000). Usually in non-magnetically shielded environment, the fluctuation of power frequency interference is about nanoTesla (nT) level. Hence, some notch filter circuits were designed to eliminate power frequency interference and to prevent circuit saturation. As the bio-magnetic fields distribute in the low frequency domain, we filtered out the frequency above 200 Hz. In the last part performance testing is carried out. We utilized a long enough straight wire to generate weak magnetic field for sensitivity testing, we could infer that the bio-sensor sensitivity is near to 10pT in non-magnetically shielded environment.
Keywords: Amorphous wire, Bio-magnetic field, GMI sensor, Pico-Tesla bio-magnetic sensor.
Title: Circuit Designing of Bio-Magnetic Sensor Using Giant Magneto-Impedance Effect
Author: Mrs. Nilima A. Warade
International Journal of Engineering Research and Reviews
ISSN 2348-697X (Online)
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