A thermographic approach is used to determine the temperature of an aluminium nitride hot plate as a glass substrate heater for depositing thin films by spray CVD (Chemical Vapour Deposition). The true temperature of the hot plate is determined by measuring its emissivity and the background temperature. The emissivity is found by means of a commercial infrared camera in the temperature range of [40°C, 540°C] with a better than 3% accuracy. The measured thermographic values are then corrected with a temperature precision of less than 4% for the highest temperatures considered. Moreover, the temperature profiles are plotted and good temperature homogeneity is observed.