Exponential signal measurement device

Abstract

A nonuniform sampling device and technique and an offset immune luminescent lifetime estimation provides for sensing a gaseous presence and magnitude such as O2 levels or concentration. The partial pressure of O2 closely correlates with the lifetime of the luminescence quenched by O2. Lifetime measurements are preferred over intensity measurements because of their robustness to factors such as variations in the optical path. The disclosed approach, implemented in 180 nm CMOS, features a specialized AFE (Analog Front End) that obtains the luminescent lifetime information with 1) low noise and 2) leverages time-gated excitation, removing the need for optical filters to extract the luminescent response from the excitation light. The lifetime (τ) is calculated using the time differences between equal voltage steps and 4) a measured mean error is as accurate as 0.3%.

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