Design Of Multi-Channel Analog Signal Source In General Test Equipment

In this paper, the analog signal source with high-precision DC output and fast rising and falling square wave signal output, and impedance testing is designed.High-precision DC signal is as testing of the static characteristics of the system, square wave signal is as testing the dynamic characteristics of the system.According to the test needs,this paper proposes a realizable method of signal source: Combining DDS principle and using high-precision DA convertor build waveform reconstruction circuit,using electronic switch realize multichannel signal output; On this basis, realizing low delay square wave signal output by Switching two different amplitude DC signals with SPDT; Realizing the impedance test by sampling and testing voltage of series resistance with the AD convertor; Realizing real-time programmable of signal source by real-time downloading waveform data from the computer that connected test bench by USB bus.Ideal square wave signal is regard as step signal containing infinite frequency components, and it can be using to test with infinitely wide bandwidth. the real step signal is non-ideal "step signal with some latency ,and the method errors caused by latency are inevitable when the system dynamic characteristics are tested with non-ideal"step signal", at the same time narrowing the testing bandwidth. this paper discussed the relationship between the three above.Before the hardware designed, detailed theoretical analyses and quantitative description for the key factors on effecting the precision of signal source were are given, and when debugging in hardware circuit is completed, on the base of analysis, errors estimation were verified with experimental results. As for low-latency square wave signal ,the square-wave signal is a "overshoot" with oscillation that was found by the early experiments. The paper have analysed this phenomenon,and,conclude that damping coefficient of the system is smaller by the analysis, solution is given.Finally, the results of experiment show the signal source complete the desig requirements and the various technical indicators.