甲烷检测中电压噪声的二次量化抑制及其实验研究

为了分析并抑制中红外甲烷检测中模数转换器(ADC)参考电压噪声对检测性能的影响,本文理论推导了待测浓度和电压波动的关系式,计算了电压波动对ADC实际分辨率的影响。一方面,为了降低噪声水平,设计了一种三级稳压电源,使参考电压的平均波动由原来的2mV降至0.6mV;另一方面,考虑到噪声无法避免,不同待测电压对应的数字量彼此交叠,致使无法精确测量各性能参数,本文提出了一种新型二次量化抑制方法,以有效消除电压噪声的不利影响。在不同的ADC参考电压噪声水平下,利用提出的二次量化抑制方法,实验测试了系统稳定性、精度、灵敏度和检测下限等性能。结果表明,当ADC参考电压的平均波动由2mV降至0.6mV时,测量精度可由12.9%降至5.0%以下,检测下限可由约26×10-6降至20×10-6。最小检测下限处的检测灵敏度可由约30×10-6降至20×10-6。这些证实,本文给出的基于二次量化思想的噪声抑制方法是可行的,并且该方法也可用于其它具有类似机理的气体检测。

Experimental study of a voltage-fluctuation suppressing method based on second-quantification in methane detection

In order to analyze and suppress the reference voltage fluctuation of the analog-digital-converter(ADC) in methane detection,the expression between methane concentration and voltage fluctuation is derived,and the effect of the fluctuation on ADC′s practical resolution is calculated.To decrease the noise level,a three-stage voltage regulator is specially fabricated,and the average voltage fluctuation drops from 2 mV to 0.6 mV.Considering that the voltage fluctuation is unavoidable,the converted digital numbers corresponding to different analogue voltages are overlapped and the detection characteristics cannot be precisely determined,a novel noise suppression method based on the second-quantification principle is proposed.Under different noise levels,the detection stability,accuracy,sensitivity and detection limit are experimentally studied.The results show that when the average voltage-fluctuation decreases from 2 mV to 0.6 mV,the detection accuracy is improved from 12.9% to 5%,the detection limit is decreased from 26×10-6 to 20×10-6,and the sensitivity under the detection limit is enhanced from 30×10-6to 20×10-6.The proposed novel second-quantification-suppressing method is experimentally reasonable,which can also be adopted in the detection of other gases with similar mechanism.