Abdelwahab Ahmed, Shishvan Omid Rajabi, Saulnier Gary J
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:1448-1451. doi: 10.1109/EMBC44109.2020.9175910.
In Electrical Impedance Tomography (EIT) the coaxial cables used to connect the electrodes to the electronics have long been a concern due to their impact on system performance. Driving the shield of the cable is useful, since it mitigates the shunt capacitance. However, this approach introduces complexity and, sometimes, stability issues. Using "active electrodes", i.e. placing the front end of the electronics at the electrode end of the cables, is also helpful but can introduce packaging and hygiene problems. In this paper, a new type of high-precision current source is described and its performance is studied when driving loads through a coaxial cable. This new current source adjusts its current output to compensate for current lost in any shunt impedance to ground, including the shunt losses in the cable. Experimental results for frequencies up to 1 MHz are provided, comparing performance with resistive and complex loads connected without a cable, with 1 m of RG-174 coaxial cable with a driven shield, and 1 m of RG-174 coaxial cable with a grounded shield. The results for all 3 cases are similar, demonstrating that the source can provide satisfactory performance with a grounded-shield cable.
在电阻抗断层成像（EIT）中，用于将电极连接到电子设备的同轴电缆长期以来一直是一个问题，因为它们会影响系统性能。驱动电缆的屏蔽层是有用的，因为它可以减轻并联电容。然而，这种方法会带来复杂性，有时还会出现稳定性问题。使用“有源电极”，即将电子设备的前端放置在电缆的电极端，也很有帮助，但可能会带来封装和卫生问题。本文描述了一种新型高精度电流源，并研究了其通过同轴电缆驱动负载时的性能。这种新型电流源会调整其电流输出，以补偿在任何对地并联阻抗中损失的电流，包括电缆中的并联损耗。提供了高达1 MHz频率的实验结果，将其性能与未使用电缆连接的电阻性和复数负载、带有驱动屏蔽层的1米RG - 174同轴电缆以及带有接地屏蔽层的1米RG - 174同轴电缆进行了比较。所有三种情况的结果相似，表明该电流源使用接地屏蔽电缆时能够提供令人满意的性能。
