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Magnetic field exposure and behavioral monitoring system
Author(s) -
Thomas A.W.,
Drost D.J.,
Prato F.S.
Publication year - 2001
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.67
Subject(s) - electromagnetic coil , magnetometer , electrical engineering , magnetic field , physics , amplifier , search coil , optics , acoustics , nuclear magnetic resonance , engineering , magnetic flux , cmos , quantum mechanics
Abstract To maximize the availability and usefulness of a small magnetic field exposure laboratory, we designed a magnetic field exposure system that has been used to test human subjects, caged or confined animals, and cell cultures. The magnetic field 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 amplifier via digital to analog (D/A) converter. A 9 pole zero‐gain active Bessel low‐pass filter (1 kHz corner frequency) before the amplifier input attenuated the expected high frequencies generated by the D/A conversion. The magnetic field was monitored with a 3D fluxgate magnetometer (0–3 kHz, ± 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 floor, connected to an analog to digital converter. Lighting was provided by 12 offset overhead dimmable fluorescent 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 Ω, 1.2 mH), 1.75 m coil (0.32 Ω, 1.4 mH), and 2 m coil (0.38 Ω, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at ± 463 μT, 1 kHz at ± 232 μT, 150 μs rise time from −200 μT pk to + 200 μT pk (square wave) and is limited by the maximum voltage ( ± 146 V) of the amplifier (Bessel filter bypassed). Bioelectromagnetics 22:401–407, 2001. © 2001 Wiley‐Liss, Inc.