The hygrometer, also known as the moisture meter or dew point meter, is used to measure the humidity of the flue gas emitted by the pollution source and convert the concentration of the wet flue gas into the dry flue gas concentration accordingly. It can also be used for industrial online humidity monitoring. SKA/ CIMS-SD-B type probe hygrometer (resistance and capacitance type) is used to measure the humidity of the flue gas emitted by the pollution source and convert the concentration of the wet flue gas into the dry flue gas concentration accordingly. It can also be used for industrial on-line humidity monitoring. The device can be mounted directly to the flue or chimney through the flange, and the humidity signal is output by 4-20mA or RS232.