数字化时差法超声采集卡设计与实现

Design and Implementation on Digital Ultrasonic Acquisition Card Bosed on Time-difference Method

为满足工程需要,研制出一种数字化、四通道、时差法超声采集卡。本采集卡中的关键研究方法和结果由三部分组成:首先,数模转换模块选用TLC5620,输出DC电压0~2.5V可调、精度0.01V,提供超声接收电路压控放大的压控信号;其次,门控模块选用CPLD的门控模块,门控范围1~127μs,精度0.5μs,提供回波的门前沿和门宽控制信号;最后,时间测量模块选用TDC-GP1,测量范围0.1μs^1.6ms、分辨率125ps,实现超声发射与接收信号的时差测量。实测表明:本采集卡能满足透射时差法超声无损检测的要求,并可为其工程应用提供平台。

In order to meet the need of engineering, this paper designs a four-channel digital ultrasonic acquisition card based on time. The key research methods and three results of the card include： Firstly, D/A module TLC5620,which outputs voltage from 0 to 2.5 VDC with a preci sion of 0.01 V, can offer voltage control signal to VCA in ultrasonic receiving circuit. Secondly, gate control module used logic units in CPLD,which controls time from 1 to 127 μs with a precision of 0.5 μs, can offer signal to control forward gate and width gate for echo. At last, time measurement module TDC-GP1 can measure time difference between ultrasonic transmitting signal and ultrasonic receiving signal, which gives the measurement of time range from 0. 1 to 1.6 ms with a resolution of 125ps. A series of measurements show that, the card can meed the needs of ultrasonic nondestructive testing technology based on time-of flight transmission method, also can provide a platform for its engineering application.