在超声波测厚的场合, 通常使用带延迟块的探头。由于延迟块的介入, 使超声波传播的声时增加, 而且延迟块材料的声速会随着温度的变化而变化, 进而会影响厚度测量的准确性。设计超声测厚仪时要设计减除这多加的声时的电路, 使最终结果为被测物的真实厚度。采用不同的技术路线来实现这个功能, 会导致在不同的环境温度、不同的耦合状况、测量对象为不同材料等各种各样的应用环境下, 产生不同的效果。针对超声测厚仪“校零”这一关键点加以论述, 介绍温度对“零点”的影响, 并介绍几种目前比较流行的 “校零”的方法, 指出各个方法的优缺点。

Ultrasonic probe with delay block is always used in the process for measurement of specimen thickness. Because of the involvement of the delay block, the traveling time of the ultrasonic wave will be increased. Moreover, the velocity of the sounds of the delay block’s material varies when the temperature changes, which could influence the accuracy of the measurement of the thickness. Circuit designed to deduct those increases is requested to get the true thickness of specimen. Employing different methods to realize this function, which can result in different effects in different environment of different temperatures, different coupling situations, and different materials of specimen, and soon on. Present paper was aiming at the concept of calibration of “zero point”, which was very important to the measurement accuracy of ultrasonic thickness gauge. At last effect of calibration by change of temperature was also discussed, the most popular calibration methods used in the ultrasonic thickness gauge were described and compared.