Design And Implementation Of Software Correlator Based On LabVIEW

Dynamic light scattering technology is an effective method for measuring nanometer and submicron particles.It is widely used in chemical industry,biomedicine,eco-environmental detection,materials science,food industry and other fields.In the dynamic light scattering method,the photon correlator is a core device,and the well-designed correlator is of great significance for improving the accuracy of the autocorrelation function measurement and thus improving the particle measurement accuracy.In this thesis,a software correlator based on LabVIEW is designed,and the dynamic light scattering experiment is used to analyze the setting of related parameters and the optimization of autocorrelation function.Based on the dynamic light scattering experimental platform,this thesis presents a LabVIEW-based software correlator consisting of NI PCIe-6612 counter board,NI PCI-5402 waveform generator board and microcomputer.In this case,the board type device can be installed in the slot of the microcomputer mainframe.Since the counter board has many digital I/O pins,there is an external wiring board for it.These designs have the features of low cost,small size and easy to use.The LabVIEW-based software system complete the process from reading data,calculating the autocorrelation function to particle size inversion.The data acquisition module adopts the method of collecting and then calculating the data,which greatly increases the maximum sampling frequency.Analyzing the influence of parameter selection such as sampling time and number of relevant channels on the performance of software correlator,a more accurate autocorrelation function can be obtained when the sampling time is much large than the number of relevant channels.The local weighted regression algorithm and the segmentation autocorrelation method are analyzed and compared,and the conclusion is that the segmentation autocorrelation method has better optimization results.