| A special measuring system for liquid crystal performance based on DSP technology is researched in view of the fact that existing impedance meters can't measure dynamic performance of liquid crystal materials. In the thesis, firstly, the design idea for high-speed digital signal processing technology and signal frequency analysis is presented according to related knowledge about liquid crystal materials, system performance indexes and the measuring theories for signal amplitude and phase under noise influences. Then, the design and development of hardware and software for the system is discussed. In respect of hardware, integral circuit is designed according to the function module. A high-speed digital signal processor TMS320LF2407A is used as the core part for mass-calculation. By using its capture unit and ADC module, the signal real-time frequency and sampling is achieved. Besides, signal generator, amplifier, adjusting circuit, input-output circuit and other circuits are included to make the whole system simple and intelligent. In respect of software, the program is also designed according to the function module and written in C language, which realizes a series of management task including keyboard scanning, liquid crystal displaying, frequency measuring, data sampling and processing. Moreover, because system frequency varies with time and phase-locked technoly cann't be realized in the hareware design, software synchronization sampling is adopted to eliminate spectrum-leakage influences. A new algorithm of DIT-FFT aimed at real list is put forward to increase the performance of system. At last, the experimental datas are anlysised and a new least-square fitting curved face algorithm is applied to timely open-circuit zero tracing. Test results show that the indexes of the system are satisfying. |
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