The paper presents temperature distribution analysis in activated on-chip chemical sensor based on p-InAsSbP/n-InAsSb/n-InAs 1×3 diode array. Temperature distributions were obtained both experimentally with the use of infrared microscopy, by I-V characteristic analysis and by finite element modelling. The simulated temperature values are in reasonable agreement with experimental data, allowing one to establish a relationship between the temperature of active elements of the sensor. The relationship is important for the improvement of chemical analysis accuracy.