A Parallel Impedance Measurement System for Electrical Impedance Tomography System with Multi - Microcontroller - Unit Architecture

Abstract

In this paper, we introduce the design, development and implementation of a parallel architecture impedance measurement system for electrical impedance tomography. The system achieves a balance between speed, cost and system size. A 16-electrodes parallel impedance measurement system is designed around a phantom tank. We use an AD9834-based direct digital synthesizer module and improved Howland voltage controlled current source circuit to generate a 50 kHz constant sinusoidal current with a peak-peak amplitude up to 1 mA. The root-mean- square (RMS) potential on all the adjacent pairs of electrodes is measured directly by the analog-to-digital converter of the STM32 microcontroller unit (MCU). In order to enhance the system operation speed, a multi-MCU architecture is proposed here. 16 MCUs are connected in parallel to measure the voltage of each electrode and execute the fast Fourier transform operation at the same time, which guarantees a data collection rate of over 30 frames/s. The 16 slave MCUs use the InterIntegrated Circuit bus to communicate with the master MCU. The RMS data is then executed to obtain the impedance based on the acquired data.