Saulnier GJ, Abdelwahab A, Shishvan OR. DSP-based current source for electrical impedance tomography.
Physiol Meas 2020;
41:064002. [PMID:
32603311 DOI:
10.1088/1361-6579/ab8f74]
[Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE
EIT systems, particularly those that use a parallel, multiple source architecture, require current sources with very high output impedance. To meet this requirement, sources often use complex analog circuits and require manual or electronically-controlled adjustments. The goal is to implement a current source with simple, adjustment-free analog electronics with high effective output impedance even with significant stray impedance at its output.
APPROACH
The excitation provided to the voltage-to-current converter is adjusted to accommodate the current lost in the finite output and stray impedances. The adaptive algorithm uses the measured voltage and the previously-measured output and stray impedance to determine the needed current adjustment.
MAIN RESULTS
The structure of the source is presented along with an implementation, and experimental results that show the effectiveness of the approach for frequencies up to 1 MHz. The measured output impedance with and without the adaptive compensation are presented as well as measurements of resistive and complex loads.
SIGNIFICANCE
The new current source has low analog complexity, operates over a wide range of frequencies, and can compensate for a significant stray shunt impedance. It can be used to implement improved parallel or serial EIT systems.
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