Abstract

ALVAREZ-SIMON, Luis Carlos  and  GOMEZ-RAMIREZ, Emmanuel. CMOS temperature control circuit for MOX gas sensors. Ing. invest. y tecnol. [online]. 2019, vol.20, n.3, e036.  Epub Oct 15, 2019. ISSN 2594-0732.  https://doi.org/10.22201/fi.25940732e.2019.20n3.036.

In the last years, air pollution and the detection of harmful gases has become one important branch in research. For this reason, several sensors capable of detecting different gases have been developed, for example, chemical-resistive sensors and metal-oxide-semiconductor sensors (MOX sensors). MOX gas sensors allow the detection of multiple gases with high sensitivity and are also compatible with CMOS integration technologies. The MOX sensors combine a gas sensing element and a heating element for the gas selectivity. Currently, the modulation of the operating temperature is one of the most used techniques to improve the selectivity and stability of the MOX gas sensors. In this work, an on/off control circuit for temperature modulation in MOX sensors using resistance from Heater to monitor the temperature is proposed. This circuit allows applying different temperature modulation techniques like pulses modulation technique, periodic wave modulation technique, and control at different levels of the operating temperature for the generation of virtual arrays of sensors by a single sensor. The circuit was designed in a 180nm CMOS technology and simulated using a simple model of a commercial sensor AS-MLC from AppliedSensor. The proposed control circuit allows achieving accuracies of 0.2Ω in the Heater resistance value, which corresponds to an error of 1 °C in the operating temperature of the sensor approximately.

Keywords : Temperature control; MOX gas sensor; temperature modulation; CMOS circuit; on/off control circuit.

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