The Design And Application Of Instantaneous Signal Data Acquisition System Based On USB

With the improvements on computer science and microelectronics, the data acquisition devices, as the most important method being used in information technology, were developed towards integration, digitalization and standardization. There are many kinds of data acquisition devices for general usage. But those universal equipment may not be fit all particular users. A data acquisition system, which is used to sample instantaneous signal waveform is discussed in this thesis.The original intention of my work is to design the apparatus which will be used to inspect the defect of Pile Foundation. Pile inspection technique is very important in construction industry. It was studied for a long time by engineers all over the world.From the point of view of testing equipment, the data acquisition system with more precision and larger dynamic range is fundamental for Pile Foundation testing. At the same time, the data acquisition system is usually manipulated at construction site, thus it is necessary for the system to have some characteristics such as small, portable and easy to communicate with a note book PC. Therefore the primary aim of my work is to design the appropriate data acquisition circuit and find out the effective data communication method.The floating-point A/D conversion scheme was employed to increase the system's dynamic range. Complex Programmable Logic Device (CPLD) was also used to perform the system's function such as data sampling trigger control and data storage control, etc. ADuC812, a new type of microprocessor with full A/D converter, was utilized to fulfill the A/D conversion.To make data communication effectively and not expensive, some kinds of external bus of PC were studied in the first instance, including Fire Wire (IEEE 1394), PCI, RS-232 and so on. Finally, the Universal Serial Bus (USB) was adopted as the system's communication bus. USB has a preferable data transmission rate, support PC's plug-and-play architecture and bus-powered (Max. 500mA).A data acquisition system with the following features is realized:· Transmission rate up to 100Kbyte/s over USB;· System's dynamic range as high as 120 dB;· Multi- kind of trigger mode control;· Sampling rate as high as 100 KSps;· 12-bit A/D conversion accuracy;· 32K bytes on-board data memory;· The system, which was made up of large-scale electronic chips, is small, light and portable, and suitable for field use.A combination of analog signal conditioning technique, analog to digital converting technique, CPLD and USB technique was utilized in the design. Therefore, The system has a characteristic of high precision, large dynamic range and high transmission rate. Further more, the system is expandable and re-configurable because both CPLD and ADuC812 have In System Programmable (ISP) function.