A system for obtaining a measurement of a species of interest. The system includes one or more reference regions, a sensor region, an exciter unit, a detector unit and a processing unit. The exciter unit exposes first and second chemical transducers in the reference and sensor regions, respectively, to an excitation light while they are exposed to reference environments and an analyte, respectively. The detector unit measures responses of the first and the second chemical transducers to the excitation light. The processing unit determines a compensation for aging of the first chemical transducer from a discrepancy between the measurements of the responses of the first chemical transducer and reference responses. The processing unit applies the compensation for aging to the measurement of the response of the second chemical transducer to obtain the measurement of the species of interest in the analyte.