The compact humidity generator is connected to the TG-DTA for measurements under water vapor atmosphere with a constant relative humidity. Equipped with a polymer type humidity sensor and high precision temperature sensor, its response to various water vapor concentrations is quick and stability for longer measurement is realized. It enables the user to perform heating under a constant relative humidity. For standard furnace, it can measure from dry to 90%RH at ambient temperature; and from dry to 90%RH using the specialized furnace at ambient to 60°C through the circulator temperature control.