An integrated thermoelectric device in semiconductor technology comprising a hot side arranged in proximity to a heat source, and a cold side, providing a signal according to the temperature difference between the hot and cold sides. The hot and cold sides are arranged in such a way that their temperatures tend to equal out when the temperature of the heat source varies, i.e. when the sensor is in poor operating conditions. A measuring circuit provides useful information according to a continuously variable portion of the signal from a time when the temperature of the heat source varies. If the temperature of the heat source ceases to vary, the temperatures of the hot and cold sides eventually equal out and the signal is annulled and ceases to vary. The distance between the hot and cold sides can be less than 100 μm.