Ultrasonic flaw detector is a portable industrial non-destructive flaw detector, which can detect, locate, evaluate and diagnose a variety of defects (cracks, porosity, pores, inclusions, etc.) in the workpiece quickly, conveniently, without damage and accurately. It can be used in both laboratory and engineering site. Ultrasonic flaw detector usually emits ultrasound to the measured object, and then uses its reflection, Doppler effect, transmission, etc. to obtain the information inside the measured object and process it to form an image. Ultrasonic flaw detectors are widely used in boiler, pressure vessel, aerospace, aviation, electric power, petroleum, chemical industry, railway transportation, nuclear power, universities and other industries.

Ultrasonic flaw detectors belong to measuring instruments managed by the state according to the metrological law. The reason why it should be subject to periodic verification is, on the one hand, the requirements of the Metrology Law and the management of measuring instruments. In order to ensure the accuracy and reliability of instrument detection data and avoid accidents such as product quality, on the other hand, the instrument is a precision electronic instrument. In the process of use, the performance of some components may change, thus changing the technical parameters of the instrument. Especially when the instrument is used, it is often in the wild, at high altitude or in the harsh environment of humidity, dust and vibration. The performance of the instrument is easily affected, resulting in increased detection error or abnormal operation of the instrument. Therefore, periodic verification is needed to avoid inaccurate detection.

When the ultrasonic flaw detector is used to detect boilers, pressure vessels, railway rails, train wheel axles, etc., if cracks, holes and other dangerous defects are not found, it may cause major accidents that endanger people's lives and property, and the consequences are very serious. Because some regions or units have included it in the compulsory verification for management, periodic verification must be carried out on time. The verification regulation stipulates that the verification cycle of the instrument shall not exceed one year. Each unit can determine the calibration cycle according to the specific situation of the instrument (frequency of use, working environment). The instrument can only be put into use after it is verified to be qualified after fault repair.