Calibration curve for SnO2-based gas sensors

Abstract Even in the absence of interfering gases, the lack of stability in the response of SnO2-based gas sensors does not allow their use as measuring devices. The cause is the dependence of the conductance of the sensor, in the absence of the reducing gas, on ambient atmosphere conditions and on ageing. As a result, at the same value of the concentration of the reducing gas, the conductance of the sensor measured at different moments has different values. In this paper, based on previous calculations, a formula for conductance is derived: the parameters which depend on the ambient atmosphere conditions and on ageing, on one hand, and the sensor constants, on the other hand, are separated. Based on this formula a calibration curve, valuable at gas concentrations higher than 20 ppm, is proposed: the ratio between the conductance of the sensor in the presence of the reducing gas and the conductance in the presence of a known gas concentration versus the concentration of the reducing gas. The results obtained for C2H5OH and CO showed that during a week, using the proposed calibration curve, the errors in the measurements of the gas concentration were less than 7%.