Low Complexity System on Chip Design to Acquire Signals from MOS Gas Sensor Applications.

Juan B Talens,Jose Pelegri-Sebastia,Maria Jose Canet

doi:10.3390/s21196552

Juan B Talens, Jose Pelegri-Sebastia + Show 1 more

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https://doi.org/10.3390/s21196552

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Abstract

Analog signals from gas sensors are used to recognize all types of VOC (Volatile Organic Compound) substances, such as toxic gases, tobacco or ethanol. The processes to recognize these substances include acquisition, treatment and machine learning for classification, which can all be efficiently implemented on a Field Programmable Gate Array (FPGA) aided by Low-Voltage Differential Signaling (LVDS). This article proposes a low-cost 11-bit effective number of bits (ENOB) sigma-delta Analog to Digital Converter (ADC), with an SNR of 75.97 dB and an SFDR of 72.28 dB, whose output is presented on screen in real time, thanks to the use of a Linux System on Chip (SoC) system that enables parallelism, high-level programming and provides a working environment for the scientific treatment of gas sensor signals. The high frequency achieved by the implemented ADC allows for multiplexing the capture of several analog signals with an optimal resolution. Additionally, several ADCs can be implemented in the same FPGA so several analog signals can be digitalized in parallel.

Highlights

In order to understand the metal oxide semiconductors (MOS) which are used as gas sensors in multiple applications [1,2,3,4], we must consider them at the molecular level
We propose substituting the Analog to Digital Converter (ADC) National Instruments boards with a sigma-delta ADC implemented on an Field Programmable Gate Array (FPGA), where post-processing could be implemented in the future
Simulation Results First, we obtained the effective number of bits (ENOB) of the ADC Simulink model for a 16-bit sine input signal

Summary

Introduction

In order to understand the metal oxide semiconductors (MOS) which are used as gas sensors in multiple applications [1,2,3,4], we must consider them at the molecular level. Volatile organic compounds such as methane can react with oxygen, yielding carbon dioxide and water as products (Equation (1)): CH4 + 2O2 →CO2 + 2H2O (1). As a result of this movement of electrons, the resistivity of the gas sensor decreases and allows current flow in the sensor This type of sensor, which has a resistive output, is simple to use and inexpensive [4,6].

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