The compact humidity generator is connected to the TMA for measurements under water vapor atmosphere with a constant relative humidity. This system is for water vapor generation at ambient or above ambient temperatures. It adopts the 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. The setting of the relative humidity is achieved by the PC station and synchronizes with the temperature program. 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.