混凝土CT中数据采集系统设计

Design of data acquisition system in concrete CT

混凝土超声层析成像仪作为现今混凝土质量检测的主流仪器,其数据采集系统的性能好坏决定了该仪器检测结果的可信度。选用ANALOG DEVICES公司的16 bit、最大采样频率25 MHz的模数转换芯片LTC2203作为该系统的核心元件。放大调理电路由可调增益放大器AD603和差分芯片THS4521组成。将超声波探头采集到的信号进行放大并差分输出给LTC2203。考虑到数据传输的可靠性和传输速度,在FPGA内,用FIFO对数据进行缓冲并通过DMA搬运至SDRAM中。通过串口将数据传输给PC端的MFC程序,对采集到的数据进行处理。实现了对频率范围至少在1 kHz^500 kHz内的超声波探头的匹配,且等效输入噪声在57.4μV左右。经测试,该数据采集系统能较好的还原被测数据,提高了混凝土超声层析成像仪的可靠性。

Concrete ultrasonic tomograph is the mainstream instrument for quality testing of concrete today. The performance of the data acquisition system determines the credibility of the instrument. The 16-bit, 25 MHz analog-to-digital conversion chip LTC2203 of ANALOG DEVICES is selected as the core component of the data acquisition system. The analog signal collected by the ultrasonic probe is transmitted to the amplification conditioning circuit composed of AD603 and THS4521, and the digital signal converted by LTC2203 enters the FIFO. Then, under the control of the soft core Nios ⅱ of the FPGA, the data in the FIFO is transferred to the SDRAM through the DMA, and finally the data is transmitted from the serial port to the MFC program of the PC to display the collected data. Finally, the matching of ultrasonic probes within the frequency range of at least 1 KHz^500 KHz is achieved, and the equivalent input noise is about 28.7 μV. Through testing, the data acquisition system better restore the measured data, and greatly improving the reliability of concrete ultrasonic tomography instrument.