Bridge crane lifting rope swing angle measuring device and use method

The invention discloses a bridge crane lifting rope swing angle measuring device and a use method. The bridge crane lifting rope swing angle measuring device comprises a closed box disposed at the end, close to a lifting appliance, of a trolley and used for accommodating gas with preset mass, a light rod, an air pressure detection unit and an information processing unit; the first end of the light rod is connected with a lifting rope, the second end of the light rod is connected with the closed box, and the light rod is used for pushing and pulling the closed box when the lifting rope swings so as to change the size of the closed box; the air pressure detection unit is arranged in the closed box and is used for detecting the air pressure corresponding to the volume of the closed box; and the information processing unit is connected with the air pressure detection unit and is used for obtaining the swing angle of the lifting rope according to the air pressure corresponding to the volume of the closed box. Acco