Pneumatic film through low temperature single seat control valve and pneumatic film through low temperature double seat control valve are one of the varieties of pneumatic actuators. It has been widely used in automatic control of industrial production processes such as petroleum, chemical and metallurgical industries. It is especially suitable for the regulation of medium (such as liquid oxygen, liquid nitrogen, etc.) at -60~250℃. In order to ensure the accuracy of regulation, valve positioner must be equipped.