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1.问题的提出在振动信号尤其是冲击信号、瞬态信号的数据采集时,通常在采集前无法预知信号的大小,因而只能凭经验在采集前设定放大器的增益.但如果放大倍数设置大了会引起过载,致使采集的信号失真,而放大倍数小了则会使A/D转换后有效位数过少,信噪比太低,致使信号捕捉失败.另外,即使事先凭经验设置的放大倍数合适,对冲击响应信号采集也存在问题.因冲击响应信号是随时间衰减的,特别是在结构的阻尼较大时,冲击响应信号的衰减是很快的,如果对此类信号在整个时间历程上施以相同的放大倍数,则开始时由于信号较大有足够的信噪比,但随着时间增长,信号极剧衰减,则信号会被采集系统的噪声或A/D转换器的量化噪声淹没.这一问题是普通数据采集系统不能解决的.
1. Proposing the problem In the vibration signal, especially the impact of the signal, the transient signal data acquisition, usually before the acquisition can not predict the size of the signal, which can only empirically set the amplifier gain before acquisition.But if the magnification settings Large will cause overload, resulting in the collection of signal distortion, and the smaller the magnification will make the effective number of A / D conversion is too small, the signal to noise ratio is too low, resulting in signal capture failure.In addition, even prior experience set The magnification is appropriate, the acquisition of the impact response signal is also problematic.As the impact response signal is decayed over time, especially in the structure of the larger damping, the impact of the response signal attenuation is very fast, if such signals in the whole Applying the same magnification to the time history begins with a large enough signal-to-noise ratio for the signal, but as the signal fades over time, the signal will be picked up by the system noise or the A / D converter’s Quantitative noise submerged. This problem can not be solved by ordinary data acquisition system.