An approach for the evaluation of sensor array efficiency is proposed. The reproducibility of sensor responses and the uniqueness of chemical images (CI) formed by the array are considered as dominant factors that determine sensor array functionality. The key feature of the method is representation of array response as a numerical function of sensors responses. This allow making mathematical operations with CI. The dispersion of CIs of given set of analytes can serve as a measure of their uniqueness. The coefficient of covariance in the set of measurements expresses their reproducibility. The rate of influence of both reproducibility and CI uniqueness on the discriminating ability is shown qualitatively on the example of three QCM sensor array with metal phthalocyanines sensitive coatings. The illumination of sensors surfaces in the Q‐band region of Pc’s adsorption spectra was applied as a factor affecting both …