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Sensors 2018, 18(2), 654;

Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors

Micro and Nano Technologies Group, Electronic Engineering Department, Universitat Politècnica de Catalunya—BarcelonaTech, 08034 Barcelona, Spain
MINOS-EMaS Group, Electronic Engineering Department, Universitat Rovira i Virgili, 43003 Tarragona, Spain
Author to whom correspondence should be addressed.
Received: 31 January 2018 / Revised: 19 February 2018 / Accepted: 19 February 2018 / Published: 23 February 2018
(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)
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Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must be compensated by average temperature produced by the control loop, which is the new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements. View Full-Text
Keywords: sigma-delta modulation; metal-oxide sensors; gas sensors; electrochemical impedance sigma-delta modulation; metal-oxide sensors; gas sensors; electrochemical impedance

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Kowalski, L.; Pons-Nin, J.; Navarrete, E.; Llobet, E.; Domínguez-Pumar, M. Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors. Sensors 2018, 18, 654.

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