Design Of Data Acquisition System For Crack Eddy Current Testing

Modern equipment often need to run in high temperature, high pressure, high speed and high load conditions, the defects of the components such as crack and damage will inevitably reduce the reliability of equipment, even lead to the occurrence of accidents, therefore, the detection of these defects is very important to the protection of equipment operation and personal safety. Pulsed eddy current testing technology is a new developed eddy current testing technology, in addition to its high detection sensitivity, high speed and non-contact measurements advantages; it also had the ability to detect the surface cracks and damage information. Data acquisition is an extremely important part which will directly affect the precision and accuracy of the eddy current testing. The main contents of this paper are to design a data acquisition system of crack detection, implement the model identification of the static characteristics for the sensor and completed the preliminary design of the detection experiments.Based on the theory of pulsed eddy current testing technology, this paper designed a set of two-channel eddy current crack detection data acquisition system, the system had the ability to accurately acquisitioned different types of signals, and processed the collected data for real-time. The acquisition system used high performance microcontroller and programmable logic device (CPLD) EPM7128 as the core control device, implemented the data acquisition by 16-bit A/D converter and its peripheral circuits, the data collected was transmitted to the host PC by real-time serial communication. The designed acquisition system was mainly consisted of the hardware circuit block and software module: hardware design mainly included the design of signal amplification, A/D conversion, CPLD interface circuit and MCU communication circuit module, and completed the PCB layout diagram and circuit board welding; In software design, including the lower machine program design and host computer data processing program design. Debugging results showed that the system had simple structure,stable performance during acquainting two-channel signals at the same time, the system could better meet the requirements of the crack signal acquisition.For the eddy current sensor was a key device in detection system, the accuracy of its detection signal played a decisive role to the performance of the data acquisition system and the whole detection system. The non-linearity and temperature drift characteristics of the sensor are important factors affecting sensor performance; this paper adopted FLANN to implement the model identification and MATLAB simulation.Finally, the paper raised the experimental program of the entire detection system and preliminary design of the experimental platform. As time is tight and limited, the study of this topic has many things that need improvement and further study; these are described in the conclusion and outlook part of the thesis.