供气相色谱仪使用的热导检测器的设计与实现

为了提高气相色谱仪用热导检测器的性能,设计了热导检测器的精密恒流源和差压检测电路。恒流源由场效应管IRF460、运算放大器AD8672和线性光耦HCNR201构成,低噪声电桥差压检测电路由2片AD8597构成。建立了差压检测电路的噪声模型,计算了噪声理论值。实际测试结果表明,该热导检测器的基线噪声达到4 μV, 50 min的基线漂移为15 μV,恒流源波动接近1 μA,优于现有热导检测器的技术指标。所介绍的设计方案和噪声分析方法对热导检测器的电路设计有较大的参考价值。

Design and implementation of thermal conductivity detector for gas chromatography

In order to improve the performance of thermal conductivity detector (TCD) for gas chromatography, a precision constant current source circuit and a difference voltage detection circuit were designed. The constant current source was designed with a field effect tube IRF460, operational amplifiers AD8672 and a linear optical coupler HCNR201. The difference voltage detecting circuit was designed with two pieces of AD8597. The noise model of the difference voltage detecting circuit was established and the theoretical value of minimum noise was calculated. The experimental results showed that the baseline noise of TCD came up to 4 microV, that the baseline drift of TCD came up to 15 microV in 50 min, that the fluctuation of constant current source was about 1 microA, which were superior to current technical specification of existing TCD. The introduced design scheme and noise analysis method have reference value for new TCD design.