Design Of Multi-channel Synchronous Data Acquisition System

Multi-channel synchronous DAQ equipment is mainly used in such large-scale test tasks as aerodynamics analysis,physiological electrical signal acquisition,mechanical state monitoring,phased array,etc.The characteristics of these tasks are that they have requirement for more parallel acquisition channels and good synchronization performance.Aiming at the shortcomings of insufficient channels and poor synchronization performance of existing DAQ equipment,this paper designs a modular DAQ system with 224 parallel acquisition channels and high synchronization performance.Firstly,this paper analyzes the significance of the synchronization performance in the DAQ tasks,and analyzes the indicators required by these system.Secondly,according to the indicators,the modular system design scheme based on PXIe bus is proposed.And on this basis,the system design is discussed from three aspects of hardware circuit,firmware logic and system software.In the hardware design,the design of data flow path is first introduced from the aspects of analog signal front-end conditioning and the test data storage and transmission;secondly,according to the analysis of the PXIe backplane working mechanism and principle,it introduces the design of clock signal path and the source and distribution of clock synchronization error in detail;finally,the power management path is designed.In the design of firmware logic of DAQ module,it adopted the top-down design method.The firmware logic consist of four parts: TLP encoding and decoding logic,external interface logic design,custom register and multi-card synchronous logic.In the system software design,device driver for different function classes is built,and the configuration and working process of interrupt and DMA are introduced in detail;QT is used to design the computer software panel for system control and data display.By setting up the test environment,this paper tested 4 system's performance indicators in the end,including sampling accuracy,dynamic performance,clock synchronization error and phase difference resolution accuracy.The multi-channel synchronous data acquisition system designed in this paper can support up to 224 channels of parallel sampling.Experimental data show that the system absolute sampling accuracy at full range is 1‰ after calibration;the SINAD is better than 100 d Bc;the sampling clock synchronization accuracy between different DAQ module is better than 500ps;aiming at 1k Hz&10V sinusoidal signal,the resolvable minimum phase difference is better than ±0.050°,which significantly improves the indicators of the number of test channels and synchronization performance.