It is very popular that TOFD technique is wildly utilized home and abroad and that is proved with experimental studies done by European and American countries showing that TOFD technique is a testing method of higher precision, relibility and safety. A transmitter- -receiver mode is adopted to send ultrasonic pulse to an object， if lateral wave is received before bottom reflected wave, the tested object is faultless; if diffracted wave appears between lateral wave and bottom reflected wave, time of the transmission is calculated to find defect. Thus the probe is the key in TOFD technique .
Changzhou Changchao Electronics Research Institute and Changzhou Changchao Testing Equipment Co., Ltd. were founded in 1980, located in Changzhou, Jiangsu, covering an area of 17,000 square meters. They are entities that produce ultrasonic probes. After years of hard work and accumulation of experience, they are engaged in non-destructive testing. Obtained a high reputation and popularity in the industry. The company has multiple sets of internationally synchronized ultrasonic testing equipment, with technical centers, R&D centers, and testing centers. It is the only high-tech enterprise in the domestic non-destructive testing industry that integrates development, design, production and processing. Products are widely used in nuclear industry, aerospace, shipbuilding, petroleum, chemical, metallurgy and other industries. The high standards, good quality and after-sales service system have won praise from users.