RESUMEN
ObjectiveA general experiment platform of electrical impedance tomography(EIT) based on field programmable gate array(FPGA) was designed to meet the requirements of EIT digital measurement.A digital current source and the research on digital demodulation method was completed.MethodsFor construction of the experiment platform,DDS module,D/A and A/D interface module,digital demodulation module and RS-232 communication module were all integrated in one FPGA chip.ResultsThe source can provide multi-frequency excitation signals of 2 mA in the range of 6.1-390.6 kHz.The output impedance of the source was higher than 190 kΩ.Both the real and the virtual information of measured impedance could be extracted.ConclusionMeasurements based on bioimpedance-equivalent circuit model verified the validity of the platform.The research results of this paper provides a foundation for the construction of a practical EIT system.
RESUMEN
A master-slave electrical impedance tomography (EIT) system for body complex impedance based on digital signal processor (DSP) is designed in this paper. Used as the master computer, a PC performs the image reconstruction and display on time, while DSP carries out such tasks as electrode selection, data acquisition and data communication with the master. Based on DDS technique, the signal generator can create the sine wave signals, and it's amplitude, frequency and phase can be continuously adjusted. The designed feedback unit can improve the linearity and the stability of the voltage-controlled current source effectively. Undersampling technology and digital demodulation technology are used in this system in order to attain the information of real and imaginary components of the body complex impedance. Back projection method is adopted to reconstruct the image in this system. Experimental results show that this system improves the data acquisition speed and the image resolution.