EXPANDED UNCERTAINTY ANALYSIS OF A LOW-COST DATA ACQUISITION SYSTEM FOR ELECTRICAL IMPEDANCE TOMOGRAPHY
Name: ERON TALISSON DIAS LOURETT
Publication date: 06/11/2025
Examining board:
Name |
Role |
|---|---|
| ADRIANA MACHADO MALAFAIA DA MATA | Examinador Externo |
| BRUNO FURTADO DE MOURA | Coorientador |
| HENRIQUE MASSARD DA FONSECA | Examinador Externo |
| MARCIO FERREIRA MARTINS | Presidente |
Summary: This study presents a comprehensive investigation into the development of a low-cost data acquisition system, named KAP2, designed for use in Electrical Impedance Tomography (EIT) to measure multiphase flows. The motivation for this work stems from the need for economically viable alternatives to conventional tomographic systems that do not compromise measurement
accuracy. The KAP2 system comprises seven key modules: a sinewave generator based on Direct Digital Synthesis (AD9850), a modified Howland current source employing AD827J operational amplifiers, an instrumentation amplifier (INA128P), a low-pass filter, an RMS to-DC demodulator (AD536AJQZ), an Atmel SAM3X8E microcontroller (Arduino Due), and multiplexers (ADG506AKNZ). The methodology involves an individual uncertainty analysis for each module using LTspice-based circuit simulations, with Monte Carlo methods employed to account for component tolerances. Resistors were modeled with a 1% tolerance under a Gaussian distribution, while capacitors were modeled with a 5% tolerance. This approach provides a realistic assessment of the system’s behavior under practical operating conditions. The results reveal the following performance metrics for each module: the sinewave generator exhibited an uncertainty of 0.123% and the maximum error is 1.406%; the modified Howland current source, 0.377%; the instrumentation amplifier, 0.095%; the low-pass filter, 0.136% at an operating frequency of 20 kHz; the RMS-to-DC demodulator, approximately 1.0%; the 12-bit microcontroller, 1.351%; the analog multiplexers, 0.487% for current injection and 0.545% for voltage measurement. An overall uncertainty analysis, based on the root-sum-square (RSS)
method of individual uncertainties, yielded a global uncertainty of 2.517% for the KAP2 system. This result represents a reasonable trade-off between cost and precision, making the system suitable for real-time monitoring in multiphase flow applications.
Keywords: Electrical impedance tomography. Multiphase flow. Expanded uncertainty. Low cost data acquisition. Monte carlo method
