| In complex electronic systems,the use of modular design is one of the current trends.High-performance broadband digital oscilloscope is divided into analogue channel module,acquisition module,storage module,software module,etc.,in which the channel module is one of the core modules of the digital oscilloscope system.As the analog channel needs to be measured by the variety and quantity of parameters,the test process is complex and tedious,the manual test efficiency is low,the data is easy to miss and easy to make mistakes,the formation of test reports take a longer time.In order to solve the above problems,this thesis analyses the principle composition of the oscilloscope’s analogue channel,builds a special automatic test system according to the testing requirements of the analogue channel in a high-speed broadband oscilloscope project,carries out software design and realizes the automatic testing of the analogue channel module,as follows.1.Firstly,with the principle of the composition and structure of the analog channel module,the testing requirements of the analog channel were analyzed,an automatic test system composed of arbitrary waveform generator,RF source and high-speed acquisition card based on USB bus control is built,and the overall design of test software is carried out with the help of Visual Studio platform,which includes the acquisition data analysis and processing module,instrument automatic control module,analogue channel circuit control module,and automatic test module.2.The instrumentation and control commands required for testing different functional states and parameters of the analog channels were analyzed and the underlying software design was carried out.For the low-frequency amplitude class parameters,the control arbitrary waveform generator is used for testing,and the criteria for the normal operation of the control circuits such as analog channel input impedance,coupling method,bandwidth limit,trigger source,etc.are analyzed,and the corresponding software design implementation flow is given;in order to solve the problem of low efficiency of manual detection of the initial parameters of the analog channels,the automatic detection method is optimized using the dichotomous method and the flip-flop method.3.Focusing on the influencing factors and testing schemes of seven parameters such as gain range,bias voltage range,bandwidth,open circuit noise,consistency of high and low frequency square wave’s amplitude,transient response of impulse,harmonic distortion,etc.,the automatic testing process and algorithm are designed.For the bandwidth test,the point frequency measurement method is used;for the problem that the AC-DC gain is inconsistent due to the high and low frequency separation path in the impedance conversion circuit,the consistency of high and low frequency square wave’s amplitude method is used for testing.Finally,the software functions are tested and verified.The correctness of the channel module circuit control function was verified by testing.After experiments,the automatic test time for the analog channel is about 5min,and the test data can be previewed and test reports can be generated,making the test efficiency and test completeness of the analog channel module significantly improved. |
