Abstract
Metal oxide (MOX) gas sensors sensitively respond to a wide variety of combustible, explosive and poisonous gases. However, due to the lack of a built-in self-test capability, MOX gas sensors have not yet been able to penetrate safety-critical applications. In the present work we report on gas sensing experiments performed on MOX gas sensors embedded in ceramic micro-reaction chambers. With the help of an external micro-pump, such systems can be operated in a periodic manner alternating between flow and no-flow conditions, thus allowing repetitive measurements of the sensor resistances under clean air, , and under gas exposure, , to be obtained, even under field conditions. With these pairs of resistance values, eventual drifts in the sensor baseline resistance can be detected and drift-corrected values of the relative resistance response can be determined. Residual poisoning-induced changes in the relative resistance response can be detected by reference to humidity measurements taken with room-temperature-operated capacitive humidity sensors which are insensitive to the poisoning processes operative on heated MOX gas sensors.
Highlights
Resistive metal oxide (MOX) gas sensors are low-cost sensors which are sensitive to a wide variety of toxic and combustible gases [1,2,3,4,5,6]
In the second part of the paper, we show that such control signals for the evaluation of Resp can be provided under field conditions when MOX gas sensors are embedded into tiny micro-reaction chambers
Such micro-reactor systems allow the embedded gas sensors to be periodically operated under reference air and test gas conditions, providing pairs of measurements of R0 and R gas at closely similar times ti and ti+1, with ∆t being small enough to exclude any sizeable drifts in R0 and ∆R during that time
Summary
Resistive metal oxide (MOX) gas sensors are low-cost sensors which are sensitive to a wide variety of toxic and combustible gases [1,2,3,4,5,6]. Such degradation processes have always remained a problem of practical concern and precluded MOX gas sensors and sensor arrays from penetrating fields where quantitative measurements need to be made or where safety-critical alarm functionalities are to be provided [31,32] Attempting to ameliorate this situation, we show in this paper how the effects of sensor degradation can be detected and partially corrected to attain higher levels of signal quality, under conditions of practical field operation. In the second part of the paper, we show that such control signals for the evaluation of Resp can be provided under field conditions when MOX gas sensors are embedded into tiny micro-reaction chambers Such micro-reactor systems allow the embedded gas sensors to be periodically operated under reference air and test gas conditions, providing pairs of measurements of R0 and R gas at closely similar times ti and ti+1 , with ∆t being small enough to exclude any sizeable drifts in R0 and ∆R during that time. A brief discussion on the current state of the art, possible future developments and optimization issues completes this paper
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