Design of a current source with high stability for brain electrical impedance tomography system

    SHI Xueª²Tao, YOU Fuª²Sheng, HUO Xuª²Yang, FU Feng, LIU Ruiª²Gang, DONG Xiuª²Zhen

    Department of Medical Electronic Engineering, School of Bioª²medical Engineering, Fourth Military Medical University, Xi¬ðan 710033, China

    ¡¾Abstract¡¿ AIM: To improve the stability of the current source for brain electrical impedance tomography (EIT) data acquisition system. METHODS: A shield guard technique was employed to minimize the shunting effect of the stray capacitance of wires between electrodes and current source. At the same time, an output current compensating method was adopted to compensate the current loss caused by the multiplexer¬ðs stray capacitance. RESULTS: The simulation results showed that after those methods were used, the maximum relative current error on a 1.5 k¦¸ load dropped from 7% to 0.4% in working frequency range, and the practical results also showed that the final maximum relative current error on this load was less than 1%. CONCLUSION: The shield guard method for wires and the output current compensating method for current source can effectively improve the stability of current source¬ðs output current. ......