Theory of self-diagnostic sensor array devices using gas-sensitive resistors

The principles of operation of self-diagnostic gas-sensitive resistors are described. Such sensors use arrays of electrodes, on a single device, to probe the concentration profiles of target gases. Theoretical treatments are presented to show the application of such devices in distinguishing gases with differing ratios of reaction to diffusion rates, compensating for relative humidity, and detecting poisoning of the gas-sensing material. The transient behaviour of the devices is also modelled, demonstrating their potential use for resolving mixtures of gases having differing kinetic timescales, by producing a ‘gas chromatograph’ type of result.