A Compact 16 Channel Embedded System with High Dynamic Range Readout and Heater Management for Semiconducting Metal Oxide Gas Sensors

Abstract

The simultaneous operation of multiple different semiconducting metal oxide (MOX) gas sensors is demanding for the readout circuitry. The challenge results from the strongly varying signal intensities of the various sensor types to the target gas. While some sensors change their resistance only slightly, other types can react with a resistive change over a range of several decades. Therefore, a suitable readout circuit has to be able to capture all these resistive variations, requiring it to have a very large dynamic range. This work presents a compact embedded system that provides a full, high range input interface (readout and heater management) for MOX sensor operation. The system is modular and consists of a central mainboard that holds up to eight sensor-modules, each capable of supporting up to two MOX sensors, therefore supporting a total maximum of 16 different sensors. Its wide input range is archived using the resistance-to-time measurement method. The system is solely built with commercial off-the-shelf components and tested over a range spanning from 100 Ω to 5 GΩ (9.7 decades) with an average measurement error of 0.27% and a maximum error of 2.11%. The heater management uses a well-tested power-circuit and supports multiple modes of operation, hence enabling the system to be used in highly automated measurement applications. The experimental part of this work presents the results of an exemplary screening of 16 sensors, which was performed to evaluate the system’s performance.

Research on Micro-Fault Detection and Multiple-Fault Isolation for Gas Sensor Arrays Based on Serial Principal Component Analysis

“…In recent years, metal-oxide semiconductor (MOS) gas sensors have developed rapidly, and the sensitivity and selectivity of MOS sensors have been effectively improved by improving oxide structures and using sensor arrays [19,20]. MOS sensors have become one of the most prominent choices for the sensing elements used in machine olfaction applications because of their high sensitivity, fast response, low cost, and operation ease [21,22]. However, due to the characteristics of the gas-sensitive material and the design of the sensor structure, the MOS gas sensor will malfunction during long-term use.…”

Algorithms for Automatic Data Validation and Performance Assessment of MOX Gas Sensor Data Using Time Series Analysis

“…Depending on the granularity, a screening can be a very time-consuming task (i.e., several days) and should ideally be highly automatized. In our previous work, we presented hardware solutions for automated batch sintering [6] and a sensor readout system to carry out highly automated sensor screenings [7]. Since the acquired data has to be analyzed and interpreted to achieve the final goal of finding the best fitting sensor and its optimal operating temperature for a given target, an automated measurement hardware for sensor screenings is only half way to the goal.…”

“…The system presented in our previous work [7] provides this additional data and was used for all screenings. Therefore, the extended preprocessing is applied to all measurements in the available data set.…”