Design Of Data Acquisition System Based On Photomultiplier Tube

With the constant progress of science and technology,the weak signal detection was put forward higher requirements.When in the very weak optical signal spectrum acquisition,in order to detect more weak optical signal and effectively extract the measured signal which is lost by the noise,this topic is based on the photoelectric multiplier tube to design the weak photoelectric signal acquisition system.It can detect the weak light signal at the nW level,and effectively amplify the weak signal to be measured,at the same time filter out the irrelevant noise signal,and improve the signal to noise ratio of the system.Firstly,light source modulation,and then this topic uses the Omni-150 series of optical grating spectrometer to divide the light,the spectral scanning range is 185nm-far infrared,the accuracy is 0.25nm(1200g/mm grating),minimum step up to 0.01 nm.Selecting the photo multiplier tube as the photoelectric detector,compared with other photoelectric detectors,it has the advantages of high gain,high frequency response and large signal receiving area.After in-depth study of relevant parameters and characteristics,a low noise high voltage bias circuit and a photoelectric signal output circuit of the photoelectric multiplier tube are built in this topic.To the weak photoelectric signal of the output of the photoelectric multiplier,constructing a matching conditioning circuit to amplify the weak signal and filter out the noise signal.After conditioning,the analog voltage signal through the analog digital conversion chip is converted into digital quantity,then it enter the programmable gate array(FPGA)to do the digital processing,such as signal correlation demodulation and digital low-pass filter.The microprocessor receives the data processed by FPGA and sends it to the host computer display processing platform,and finally the display processing platform draws the collected data into spectral curve.The experimental results show that the acquisition system can detect the weak optical signal with wavelength of 360-840 nm and optical power in the range of 0.1nW-0.2mW,and the peak value of the spectral response is located in the 420 nm wave.