Thomas A W, Drost D J, Prato F S
Bioelectromagnetics Western, Department of Nuclear Medicine & MR, The Lawson Health Research Institute, St. Joseph's Health Care, London, Ontario, Canada N6A 4V2.
Bioelectromagnetics. 2001 Sep;22(6):401-7. doi: 10.1002/bem.67.
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 x 1 m separation, 1.751 m x 0.875 m separation, and 1.5 m x 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 Omega, 1.2 mH), 1.75 m coil (0.32 Omega, 1.4 mH), and 2 m coil (0.38 Omega, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at +/- 463 microT, 1 kHz at +/- 232 microT, 150 micros rise time from -200 microT(pk) to + 200 microT(pk) (square wave) and is limited by the maximum voltage ( +/- 146 V) of the amplifier (Bessel filter bypassed).
为了最大限度地提高小型磁场暴露实验室的可用性和实用性，我们设计了一种磁场暴露系统，该系统已用于测试人类受试者、关在笼中或受限的动物以及细胞培养物。该磁场暴露系统由三对正交线圈组成，线圈尺寸分别为2米见方×间距1米、1.751米×0.875米间距以及1.5米×0.75米间距。每个线圈由十匝绝缘的8号绞合铜导体组成。每对线圈均通过数模（D/A）转换器由恒流放大器驱动。放大器输入端前的一个9极零增益有源贝塞尔低通滤波器（截止频率1 kHz）衰减了D/A转换产生的预期高频。通过模数转换器用三维磁通门磁力计（0 - 3 kHz，±1 mT）监测磁场。行为监测使用两台单色摄像机（垂直和水平观察线圈中心），两台摄像机均可进行视频录制，并实时进行数字式运动图像专家组（MPEG）编码到光盘。用安装在地板上并连接到模数转换器的三维测力板监测人体姿势摆动（站立平衡）。照明由12盏偏移的头顶可调光荧光轨道灯提供，并使用数字连接的光谱辐射计进行监测。串联连接的每对线圈的直流电阻、电感分别为1.5米线圈（0.27Ω，1.2 mH）、1.75米线圈（0.32Ω，1.4 mH）和2米线圈（0.38Ω，1.6 mH）。1.5米线圈组的频率响应在±463μT时为500 Hz，在±232μT时为1 kHz，从 - 200μT（峰值）到 + 200μT（峰值）（方波）的上升时间为150μs，并且受放大器的最大电压（±146 V）限制（贝塞尔滤波器旁路）。
