通过模拟机和数字机回波显示原理的比较以及对欧洲标准EN 12668-1中显示响应时间定义的解读，分析了数字机显示响应时间产生的原因，引出最高有效重复频率的概念及用途，分析了欧标对该指标测量方法存在的不足之处，及应增加考核报警指标的建议。提供了用自制仪器对多种数字机进行简单测量的原理和测量结果，以及不用测试仪器的粗略测量方法。呼吁制造厂商和用户重视该项指标的意义。

The aim of this article was to emphasize the importance of the display-response-time in order to attract the necessary attention from manufacturers and users of digital ultrasonic instruments. By comparison of echo-waves display principles between analogue and digital ultrasonic instruments, as well as the definition of display-response-time in European Standard(ES) EN 12668-1, this article explained the reason of display-response-time under digital ultrasonic instrument context, and the concepts and applications of maximum-effective-repeat-frequency. It also pointed out the deficiency of the measuring method under ES definition, and suggested examining the alarm. Moreover, this article introduced some simple methods to measure display-response-time, either by external testing-device, or by rough self-test method.