共查询到19条相似文献,搜索用时 140 毫秒
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针对气相色谱热导检测器的弱信号失真问题,研究与设计热导检测器的弱信号测量电路及其单片机控制系统,进一步提高气相色谱热导检测系统的灵敏度和可靠性。 相似文献
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热导检测器是气相色谱仪中最常用的检测器。它的灵敏度虽然没有氢焰离子化,电子捕获等检测器高,但它是一种通用型的检测器。无论有机或无机化合物试样,只要与载气的热导率有差别,就能检测出来。所以尽管十几年来,发展了各种各样的气相色谱检测器,热导 相似文献
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研究了用气相色谱电子捕获检测器(GC-ECD)和气相色谱热导池检测器(GC-TCD)测定发射药老化后N2O含量的方法。考察了电子捕获检测器和热导池检测器对N2O含量的不同测量范围和不同固定相以及不同色谱条件对测定的影响。采用GDX-104为固定相的色谱柱和热导池检测器,对不同批次发射药老化后样品中的N2O含量进行了测定。结果表明,N2O的色谱保留时间在1.6min左右,4批老化后发射药样品中的N2O含量分别为376.8、264.7、1036和1812μL/L,RSD分别为4.11%、2.64%、3.87%和0.78%。 相似文献
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利用国产102型气相层析仪配合自装的色谱电化学联用装置进行了水合肼测试的尝试,得出的肼峰信号显著大于热导检测器的肼峰信号,对于含量中水多肼少样品的测试,利用色谱电化学联用装置比纯色谱法更加有利。 相似文献
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一、引言气相色谱用的检测器不断地呈新,至今已有廿余种[1][2],但从成熟应用之程度来比较,它们中间差距尚很大。热导池和氢焰检测器等,谓之气相色谱用基础检测器,技术成熟、应用广泛,是采用量最大的一类检测器。 相似文献
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本文从设计实践的角度评述了气相色谱的近代热导检测器。它包括检测器体积和几何形状、温度控制、敏感元件以及热丝和热敏电阻两者的电学性质。 相似文献
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根据低电压集成电泳芯片柱端非接触高频电导器的结构和非接触高频电导检测的基本原理,设计了非接触电导检测电路.该电路包括AC激励信号发生器、I-V转换器、乘法运算器、低通滤波器和差分放大器.运用较少的元器件和较简单的电路形式实现了检测功能,解决了低电压电泳芯片微弱的非接触电导信号检测困难的问题.通过调节电路参数分别得到了频率为450 kHz和1 MHz,幅值为10 V的正弦信号.在此激励信号下,在集成低电压电泳芯片上对一系列不同浓度的K+溶液进行了非接触电导响应信号的测试.实验结果表明,电路能分辨的离子浓度的下限为10-9;离子浓度为10-9~10-5时,电路响应具有很高的线性度和分辨率.该电路亦可用于其它微弱电导信号检测领域. 相似文献
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新型气体热导传感器及其应用设计 总被引:2,自引:0,他引:2
气体热导传感器是利用被测组分和参考气的热导系数不同而响应的浓度型传感器。文中介绍了一种新型气体热导传感器TCS208F的特点、结构及指标,由于其输出是微弱信号,所以设计出其信号调理电路。传感器检测到的微弱信号由测量电桥调理输出,通过集成芯片AM402中的仪表放大器进行差分放大,由于远距离传输的需要,再将电压信号送入U/I变换器转换成0~20 mA的工业标准电流信号,最后再把电流信号转换为电压信号送入单片机。 相似文献
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设计了一种集激励、检测和数据采集功能于一体的毛细管电泳非接触电导检测器,采用文氏电桥振荡器产生激励信号,运用绝对值检波技术对检测信号进行处理,并设计USB数据采集电路和上位机软件,实现波形数据的采集、存储和图谱的绘制.介绍了其检测原理、电路结构及实现,使用葡萄糖(0.04 mol/L)+果糖(0.04 mol/L)+蔗糖(0.04 mol/L)样品进行了检测器重复性实验,并分离检测了6种酚酸,对检测器检测限作出评定.实验结果表明:峰保留时间和峰面积相对标准差分别小于1%和7.5%,对酚酸的最低检测限为5μg/mL(信噪比S/N =3),检测器灵敏度高、重复性好. 相似文献
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为实现导热系数的快速测定,基于一维无限大稳态导热原理,研制了一种新型三电炉结构平板式导热系数测定仪。它以MSP430F147单片机为测量控制核心,设计了相应的接口电路。相对于同类产品,在减少体积、减少测试过程中试件数量及利用PID温度控制等方面进行了良好的设计。实验结果表明,该仪器具有测试速度快、误差小、量程宽和造价低等特点。 相似文献
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系统采用微流量气体热导传感器TCS208F进行H2浓度数据采集,设计了信号调理电路,并在传感器外部设计环境温度控制电路实现传感器的恒温检测.传感器输出的微弱信号经放大电路送入微处理器S3C44B0中进行后续处理,完成H2浓度的数据采集与显示.理论研究和实验表明:该数据采集系统克服了传统热导传感器检测误差大、环境温度补偿困难等诸多问题,具有广阔的应用前景. 相似文献
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The 3ω technique has been applied to measure thermal properties of thin films and suspended wires. In this article, we report the implementation and technical design of a 3ω system to measure the thermal conductivity in small dimension structures. Alternating current is applied to a line heater that dissipates power and varies its resistance. The 3ω voltage drop across the heater provides information that determines the thermal properties of the heater or of the adjacent material. A differential bridge is used to subtract the first harmonic voltage and systematic noise. We introduce the use of a synchronous detector associated with the differential bridge to obtain the in-phase and out-of-phase components of the third harmonic signal. The combination improves the bridge method for a broad range of frequency analysis that permits either thermal conductivity and/or heat capacity measurements. 相似文献
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Yu. M. Nikolaenko Yu. G. Pashkevich P. Lemmens 《Instruments and Experimental Techniques》2002,45(6):853-857
The features of the arrangement of a procedure of measuring thermal kinetic characteristics (specific heats of films and substrates, the substrate thermal conductivity, and the thermal resistance of the film–substrate and substrate–thermostat interfaces) of film structures using a computer are described. An amplifier circuit developed taking into account the technical and procedure requirements of the method is presented. The circuit includes a wide-band dc amplifier with a differential input and a linear amplitude–frequency characteristic in the range of 0 to 2 × 106 Hz combined with a sample-and-hold circuit for controlling the dc component of a pulse signal. 相似文献
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In this paper, we describe an easy-to-use method to measure the thermal conductivity of thin films based on an electrical heating/sensing mechanism and a steady-state technique. The method used relative commonly used instruments, and without any signal processing circuit, is easy to be used in such thin-film thermal conductivity measurement. The SiO2 thin-film samples, prepared by thermal oxidation, plasma enhanced chemical vapor deposition (PECVD), and E-beam evaporator, were deposited on a silicon substrate. The apparent thermal conductivity, the intrinsic thermal conductivity of SiO2 films, and the total interface thermal resistance of the heater/SiO2/silicon system were evaluated. Our data showed agreement with those data obtained from previous literatures and from the 3 omega method. Furthermore, by using a sandwiched structure, the interface thermal resistance of Cr/PECVD SiO2 and PECVD SiO2/silicon were also separately evaluated in this work. The data showed that the interface thermal resistance of Cr/PECVD SiO2 (metal/dielectric) is about one order of magnitude larger than that of PECVD SiO2/silicon (dielectric/dielectric). 相似文献
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SUMMARY Equipment is described for the operation of thermal conductivity detectors with square-wave bridge current. The resulting ac output signal allows amplification without the need for low-level choppers. With phase-locked demodulation of the amplified signal, bridge unbalance signals of the order of 10 nV can be detected. This performance exceeds the requirements of presently available detector cells, which produce noise levels of the order of 100 nV. The instrument is compatible with most existing hot wire detectors and may be used with economical recorders. Air and other permanent gases can be reliably analyzed at levels of 0.02 μl, with detection limits of the order of 0.002 μl. This performance makes the instrument attractive in the field of air pollution and opens the way to further research in the design of low-noise detector cells. 相似文献