Obtaining Highly Selective Responses from a Bulk Tin Oxide Gas Sensor

Abstract

Generic gas sensors are commonly used for the detection of different airborne contaminants due to their high sensitivity, long life and low cost, but they generally suffer from the variety of drifts and the lack of selectivity. Different techniques have been developed for selectivity enhancement in metal oxide gas sensors, among which operating temperature modulation is well known. It has been observed that sharp pallet temperature changes provide more analyte-related information. Due to the high thermal capacitance of the device, applying step voltage pulses to a bulk tin oxide gas sensor fails to provide step pallet temperature variations. On the other hand, the low thermal capacity of the custom made microheater gas sensors renders them vulnerable to all kinds of thermal noise and agitations. A novel technique is reported for temperature modulation, which facilitates sharp temperature rises of the gas sensitive pallets in generic gas sensors [. In this technique, a sharp heating voltage spike, considerably surpassing the nominal heating voltage, is applied prior to each heating voltage step. The thermal impact of these spikes is adjusted by controlling v2dt for obtaining the closest variations to the ideal temperature profile. Here, the advantages and effectiveness of the technique are demonstrated by differentiating among iso-butanol, tert-butanol, 1-butanol and 2-butanol contaminations in a wide concentration range in air using only a single generic tin oxide gas sensor.

Innovative Approach to Photo-Chemiresistive Sensing Technology: Surface-Fluorinated SnO2 for VOC Detection

“…Among alcohols, there is a reduction in sensitivity with increasing alkyl group (primary > secondary > tertiary), which could be attributed to the increase in steric hindrance, as reported in the literature. 60 The sensing mechanism can be explained on the basis of desorption of surface-adsorbed oxygen by the VOCs, leading to an increase in electron density on the surface and thus decreasing the resistance of the sensor.…”

Comparison of different feature reduction methods in the improvement of gas diagnosis of a temperature modulated resistive gas sensor

“…In another work by Babaei and Amini, they applied temperature modulation in the form of different voltage waves and used principal component analysis (PCA) method to reduce dimensions of feature vector. By doing so, they managed to reduce the dimensions of feature vectors to three dimensions and identify four Butanol isomers [12].…”