Detection method and detection device for variable-diameter eddy current sensor

The invention relates to a detection method and a detection device of a variable-diameter eddy current sensor, which are used for in-service electromagnetic eddy current nondestructive testing of metal pipes with various pipe diameters, and are particularly suitable for nondestructive testing of local expansion parts or bumps and the like of the metal pipes. The spiral flexible diaphragm type detection sensor device is characterized in that the spiral flexible diaphragm type detection sensor device which is elastically wound in a spiral line mode is adopted, the two ends of a spiral flexible diaphragm are fixed to a sliding rail of a support in a sliding mode, the spiral outer diameter of the spiral flexible diaphragm is adjusted in a sliding mode, and the outer diameter of the spiral flexible diaphragm type detection sensor device is adjusted; the inner diameter or the outer diameter, the outer diameter of the detected metal pipe during external penetration detection, and the inner diameter of the detected m