A Time Delay Model for a Pulse Voltammetric Sensor System: Toward an E-Tongue Application

This work estimates a time delay model of a pulse voltammetric sensor system. The existing modeling techniques have been found to produce limited model fit, as the transients in the response current due to nonfaradaic electrochemical processes were left unmapped to a large extent. The incorporation of time delay in the system model has been found to improve the fit performance for such responses. Rigorous experiments have been performed on standard solutions of sodium carbonate to collect current responses from a newly developed pulse voltammetric sensor system. Motivated from the recent works, the proposed second-order plus time delay (SOPTD) transfer function models were decomposed into equivalent electrical circuits. The circuit parameters were considered as process features to assess the potential of the proposed technique toward sample discrimination purposes. Principal component analysis (PCA) was then applied to investigate the clustering propensity among the extracted features. It has been found that the features obtained from the time delay model produced significantly better clusters as compared to the existing feature extraction techniques. A cluster separability index (SI) value of 3138 has been obtained with the proposed time delay model for standard solutions as compared to the best-case SI value of 458 obtained with the existing modeling techniques. Subsequently, it can also be observed that the features extracted via the proposed model facilitate discrimination of complex natural samples like tea infusions, thereby supporting its utility for potential electronic tongue (E-Tongue) applications.