The Development Of Key Parts Of Time-resolved Spectrum System

The hardware of time-resolved spectrum (TRS) system, mostly composed of an excitation light source, a monochromator, a photomultiplier tube, an oscilloscope, a control circuit and a upper PC. The excitation light source is modulated by a frequency electrical signal, which is focused on a sample. The spectra of the emission light of sample and the excitation light are detected by monochromator, and then the optical signal was transformed to electrical signal by a photomultiplier tube (Hamamatsu 1P28). The analog electrical signal of the spectrum data was then converted into digital signal by an oscilloscope. At last, the computer can deal with the data.The small convenient type of LED source module and frequency modulated signal source module are invented at low cost. The LED source module can use high-power ultraviolet LEDs of different wavelengths, The LED is modulated by a high-frequency dynatron, which is used as a switch; signal source module use NE555 circuit as the low-frequency signal source, and use crystal oscillator as the high-frequency signal source. A simple shielded shell and BNC are designed and fixed for the PMT.Programming with C language controlled the micro-control-processor AT91SAM7S64 and kinds of peripheral circuit constitute the control circuit, which drive the stepper motor to run the monochromator for required wavelength. Communication between the control circuit and upper PC is used RS232 serial interface. In fact, the stepper motor runs all right, no matter in one step or continuously.In application, the excitation spectrum and frequency signal of the cresyl violet ethanol solution are measured. The value of the fluorescence lifetime with improved phase-demodulation method is tried to calculate out. The result is 3.86ns, compared with a result of a TCPSC equipment (4.24 ns).