Abstract
We investigate the electrode dynamics of exhaust gas oxygen sensors in order to identify the rate-determining step. The rate-determining step is the two-dimensional surface diffusion mechanism, at the exhaust gas platinum electrode. The diffusion species is the adsorbed oxygen atom. This conclusion results from the study of the transfer function of the electrode dynamic of the exhaust gas platinum electrode. This transfer function is obtained by measuring the ratio of the transfer functions of a wide range air to fuel ratio sensor operated at electromotive force ( emf) mode and pump-mode. This is made possible by utilizing the fact that in pump-mode, the electrode dynamic effect is annulled by a negative proportional feedback loop, which pumps oxygen in and out to keep the emf cells at constant regardless how the exhaust gas changes.
Published Version
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