Performance Analysis of an MLS-Based Interface for Impulse Response Estimation of Resistive and Capacitive Sensors

Abstract

This paper presents a performance analysis of a system for electrochemical impedance spectroscopy (EIS). The system, composed by an analog front-end (AFE) and a custom microcontroller (MCU) board, performs the impulse response (IR) measurement of linear and time-invariant (LTI) systems with pseudo-random excitation signals. As a novelty, a specific AFE for the interfacing of two-terminal resistive and capacitive sensors is covered in detail. The paper proposes, for the first time, a mathematical model to predict the impact of the main noise sources in the measured IR. Thanks to the proposed approach, the AFE and the system's parameters can be properly designed in order to reduce the error, thus, minimizing the energy-per-error figure of merit (FOM) as well. The AFE is realized as discrete-components circuit and it has been included in a custom MCU-based measurement system as an expansion module. The predicted results from the mathematical model, in terms of noise power, SNR, and measurement error are validated through system-level simulation and experimental measurements. The system performs the IR measurement with 1023 points, showing root-mean-square (RMS) measurement errors of 1% and 1.4% for the tested ADC sampling frequencies of 62.5 kHz and 125 kHz, respectively. These lead to excellent FOM values of 128.9 mJ • % 2 and 252.6 mJ • % 2 that outstand the state of the art.

A Multi-matrix E-nose with Optimal Multi-ranged AFE Circuit for Human Volatilome Fingerprinting

“…3 depict a block diagram and a photo of the Multisense V2 mainboard, respectively. A detailed description of the mainboard can be found in [26]. Briefly, the mainboard provides 10 resistance channels and 10 voltage channels for read-out from chemiresistive gas sensors and voltage read-out from generic sensors.…”

A 177 ppm RMS Error-Integrated Interface for Time-Based Impedance Spectroscopy of Sensors

“…Let m[n] be the MLS input of an LTI system, y[n] its output array, and h[n] its IR. The latter can be measured by cross-correlating the input array, m, with the output array, y, as follows [5,12]:…”

“…Some examples of applications of impedance analysis are bioelectrical impedance (BioZ) measurement [2], electrical assessment of the cell metabolism [1], online built-in test for DC-DC converters [3], estimation of battery parameters due to aging [4], etc. In recent years, a plethora of electronic solutions for impedance analysis, both discrete component and integrated, have been presented [5] in order to accomplish the variety of requirements needed by the applications. Compared to discrete-component solutions, integrated circuits offer the advantage of overcoming the common accuracy issues of laboratory instrumentation [6].…”

“…Compared to discrete-component solutions, integrated circuits offer the advantage of overcoming the common accuracy issues of laboratory instrumentation [6]. Moreover, integrated solutions allow for the realization of miniaturized and portable analyzers, which are suitable for modern Internet-of-Things or point-of-care devices [5,7].…”

“…Popular signals used for broadband excitation are maximum-length sequences (MLS). These are pseudo-random binary signals with unique mathematical properties, thanks to which the impedance measurement can be performed in the time domain, requiring only the digital cross-correlation as a processing algorithm [5,11]. As an example, in [6] an MLS-based measurement circuit for bio-impedance spectroscopy was implemented.…”