The Research Of Data Acquisition Technology Of Ultrasonic Detection Signal

In the process of steel materials' produce and manufacture, flaws of overlapped skin, crack inside or outside the steel materials will appear. The flaws may influent the characteristic of metal and the intensity of mechanism, which will easily bring the phenomenon of rupture and avulsion, influent the using life and quality which use steel materials include flaws, and brings hidden trouble in the safety producing. At present in the most of flaw detection method, ultrasonic detection is admittedly think to be the most efficiently detection method in detecting the inner flaw of material in and abroad. Data acquisition is the most important stage in the process of detection, it will directly influent the precision and veracity.This article was about the design of ultrasonic data acquisition, beside confirm high speed data acquisition witch can precisely rebuild the detection echo signal, it will also do real time process to the acquired data. The core device in the card is DSP, the card can realize high speed acquisition through high speed A/D and peripheral device. The system includes four parts that is the amplifier, A/D, data buffer and digital signal processor. In the core of DSP the card can process high speed data acquisition on the ultrasonic signal come from the sensor, and then DSP will deal with the data and transmit the data to the computer through USB interface. In order to resolve the impact of the avoid noise in the process of data acquisition to the detection result, the design also include method of wavelet transform to the input signal, which will wipe off the noise in the input signal, so we use wavelet transform method and db2 as the wavelet function in the wavelet family of Daubechies, in the help of time-frequency part analysis characteristic made multi-resolving capability analysis of ultrasonic signal. Different noise threshold was set in every stage, the input signal was de-noised ,and the de-noised signal was rebuilt. Using this method, the experiment proved that noise in the ultrasonic signal was effectively restrained. Experiment of high speed detection echo signal's acquisition about testing block confirm that this data acquisition card can realize high speed acquisition of detection echo signal and the acquired data can transmit to the computer through USB interface. The noise in the rebuild signal is effectively restrained through wavelet de-noise method, perfect flaw data can acquired.