Transient response of amperometric solid electrolyte oxygen sensors under high vacuum

Abstract

This paper determines the response times of amperometric solid electrolyte oxygen sensors under high vacuum conditions in experimental series with varying parameters. Such sensors can be designed with very small sizes and low power consumption and are therefore ideally suited for applications with limited resources. The interpretation of measurements with rapid variations of the oxygen concentration requires knowledge about the transient sensor behavior. It is shown that the response times are significantly reduced by controlling the cathodic overpotential with a potentiostat, compared to an operation with a constant voltage between the electrodes. The response times are a function of the overpotential, and the measured values at pressure levels of 10−5 hPa are in the order of seconds. They increase with lower pressures and decrease with higher temperatures. A model of the reactions at the cathode has been developed in order to explain the findings. It is used for simulations of the transient signal following pressure changes, and the results indicate a significant reduction of the response time by shortening the diffusion length along the electrodes.