Automatic calibration system and calibration method for digital rail welding seam ultrasonic flaw detector

The automatic calibration system comprises a calibration control terminal, a programmable attenuator and a standard signal generation module connected with a detected ultrasonic flaw detector, and the detected ultrasonic flaw detector is connected with the synchronous trigger input end of the standard signal generation module through a fixed attenuator. The signal output end of the standard signal generation module is connected with the signal input end of the tested ultrasonic flaw detector through the programmable attenuator, and the automatic calibration method comprises the following steps: setting calibration parameters, generating a gating command and automatically gating a signal channel according to preset setting information, presetting a calibration test channel based on established communication connection, and automatically calibrating the ultrasonic flaw detector according to the calibration test channel. And controlling a standard calibration signal generated by a standard signal generation modu