高湿环境下丁酮气体检测实现方法研究

针对吸油烟机气味降低度实验中,丁酮气体检测环境相对湿度较高的特点,研究了利用金属氧化物半导体气体传感器,在高湿环境下检测丁酮气体的实现方法。介绍了采用干燥剂除湿和混合纯净干燥空气除湿2种方法来降低待测气体样本的相对湿度。实验结果表明:干燥剂除湿方法会对丁酮质量分数测试结果造成较大的影响;而混合干燥空气除湿方法能够显著降低气体相对湿度,实现高湿环境下丁酮气体质量分数准确检测。所研发的系统可满足吸油烟机气味降低度实验要求。     

基于在体植入电极的生物嗅觉传感系统设计及其气味识别

目前生物嗅觉系统在气味识别方面相比于化学传感器阵列构成的电子鼻系统具有更高的灵敏度、特异性和响应速度。为了探讨生物嗅觉传感系统气味识别的可行性,构建了基于微电极阵列传感器植入大鼠嗅球构成的嗅觉传感系统,研究记录了浓度为10 mM的异丁醇、苯甲醚、香芹酮和柠檬醛4种气味刺激引起的嗅球僧帽层低频场电位信号,采用多窗谱估计算法和移动窗技术结合得到随时间分布的功率谱密度图。实验结果发现气味刺激后信号功率谱能量较多分布在gamma频段(40 Hz～120 Hz)。使用K最邻近分类方法对120组数据进行分类识别,4种气味分类正确率达到77.4%。实验结果表明该嗅觉传感系统结合多窗谱估计时频图与K最邻近分类算法可以初步实现气味识别。     

基于集成气敏传感器阵列的电子鼻系统环境响应特性分析

基于集成气敏传感器阵列和多传感器信息融合技术的电子鼻系统 ,可用于气体 /气味的定性定量识别 .在实际应用中 ,被识别样本的浓度、样本环境的温度和湿度参数等都对电子鼻系统的响应特性有较大的影响 .本文分别利用纯净空气及乙醇或葡萄酒作为载气及分析样本 ,对电子鼻系统响应特性与气敏传感器工作温度以及样本温度、环境湿度、样本浓度间的依赖关系进行了实验分析 ,并分别给出了它们间依赖关系的实验结果 .     

气体传感器特征参数分析

特征参数在气体传感器的描述、气体/气味分类、识别和量化中起着关键作用。对从气体传感器响应曲线中直接提取的典型客观特征的统计性能进行了分析。通过一个自动测试系统测试了一个微热板式气体传感器阵列对不同浓度的CO、CH4和NO2三种气体的响应,获得了一系列的响应曲线。从曲线中提取客观的稳态和动态特征进行分析,建立了一个有效的特征子集,并通过一个神经网络进行了验证。实验结果说明,使用该特征子集为输入参数的神经网络收敛速度快,误差性能小,验证了提取的特征子集的合理性。     

基于特征比值法的电子鼻农药识别系统

采用二氧化锡半导体气敏传感器、热线型和催化型气敏传感器构成气体传感器阵列,用小波降噪和数据压缩对传感器响应信号进行预处理,采用特征比值法对响应曲线进行特征提取.选取不同浓度的常用农药等10种气体用径向基神经网络进行训练和识别试验,气味识别正确率达到83.3%.     

基于电子鼻技术的烤烟过程气味变化研究

为了掌握烟叶烘烤过程中气味变化的规律,用金属氧化物半导体传感器阵列组成的电子鼻对烤烟烟气进行实时监测。详细阐述了自制的电子鼻系统和实验过程,在对样本数据进行预处理后,采用主成分分析法对样本进行分析。分析结果表明:利用电子鼻技术得出的气味综合曲线能够真实有效地反映烟叶烘烤过程中的气味整体变化趋势,并且分析得出的烤烟过程中气味变化规律与现有烟叶烘烤理论较好地吻合。     

一种新型类脂膜嗅敏传感器的研制

本文对叉指型类脂膜嗅敏传感器的设计、制作和测试进行了介绍.在微加工的化学电阻上涂敷人工合成的类脂膜可做成这种传感器.在室温气态条件下对9种气味进行了测试.对多数气味物质,器件的响应与浓度关系服从Stevens乘方定律,且各种气味引起器件膜电导改变的最小浓度与相应气味的人嗅阈值存在一定的相关性.     

基于金属氧化物气体传感器的气味罗盘的实验分析研究

设计一种由TGS2620金属氧化物气体传感器构建的气味罗盘系统。研制了气味罗盘的信号采样系统及辅助电路。在点气源及平流环境下对该系统进行了360°静态气源定位实验,提取传感器阻值响应比为特征量,并论证了该特征量与罗盘偏转角度α的对应关系。实验表明气味罗盘对相差30°方向的气源据有较大的响应差,以响应比值为特征量进行分析能够排除同类型传感器个体差异对分析结果的影响。     

基于传感器阵列的危害气体快速预警与识别方法研发

工业现场危害气体的短时突发泄漏可能是大规模泄漏的初期表现,但现有气体检测设备响应时间较长,无法有效捕捉短时突发泄漏.针对该问题本文设计了基于传感器阵列的危害气体快速预警与识别算法,通过标准实验得到传感器标准动态响应曲线簇,拟合建立传感器阵列的标准动态响应库,以监测气体传感器阵列的实时输出值与输出值变化率与标准动态响应库做对比,快速预判待测气体的种类和浓度,将预判结果与报警阈值相比较,判断是否发出预警信号.测试实验结果表明,使用该算法可以显著缩短危害气体定性定量监测的响应时间,可显著提高对突发短时泄漏的监测预警效果.     

弱化温湿度变化对气敏传感器影响的方法探究

金属氧化物气敏传感器可以实时检测识别化学气体成分,对不同化学气体成分敏感的传感器组成气敏传感器阵列,可以有效识别多种气味,进一步识别散发气味的物体及物体的状态。相比传统的化学试剂分析方法,气敏传感器阵列具有实时性、高可用性、高性价比等优点。金属氧化物气敏传感器的性能会受到温度、湿度的影响导致传感器输出值波动,对气敏传感器阵列正确识别气味产生干扰。利用温度、湿度与传感器输出值之间的能带关系构建能带模型,通过模型拟合实时温湿度及其变化对传感器输出值产生的影响偏差序列,利用计算得到的偏差值序列校正传感器输出数据,达到弱化传感器与温湿度相关性的目的。该方法应用于传感器数据采集过程后的数据预处理阶段,独立于构建完整气味识别系统中的数据建模过程。实验结果显示该方法有效增强了基于气敏传感器阵列构建的气味识别系统的目标识别率。     

A nitric oxide gas sensor based on Rayleigh surface acoustic wave resonator for room temperature operation

A Rayleigh surface acoustic wave (RSAW) resonator with polyaniline/tungsten oxide nanocomposite thin film is investigated as a gas sensor for detecting the presence of nitric oxide (NO) in air. The sensor developed in this work was sensitive to NO gas at room temperature. It is shown that the sensor had a frequency shift of 1.2 ppm when it was exposed to 138 ppb NO. The negative frequency response increased with NO concentration increasing. The response and recovery times of the NO sensor in this work were about 20-80 s. In addition, this RSAW sensor also exhibited reversibility and repeatability to the presence of NO gas. Especially, the presented sensor showed high selectivity with NO gas to separate from NO₂ and CO₂ gases.     

基于能量解析法的Air Ball Demo建模和硬件实现

从能量守恒原理入手,建立了以Air Ball高度为被控制对象,以风机PWM为输入的数学模型,推导了风机PWM占空比与悬浮小球高度间的数学关系。在MATLAB／Simulink进行了仿真测试,将建立的Simulink仿真模型生成到AS（Automation Studio）软件件平台中,通过仿真器AR000得到系统阶跃响应曲线。而后,在As环境下建立基于贝加莱PCC的控制工程,编写PWM程序,给Air Ball Demo硬件模型加载阶跃电压,实测Air Ball硬件模型的阶跃响应曲线。由仿真和实测阶跃响应曲线的数据表明,采用能量解析法建立的模型基本能反映悬浮球的实际运动特性,且具有计算量小,调节时间短的优点。     

One-step synthesis and gas sensing characteristics of hierarchical SnO2 nanorods modified by Pd loading

The hierarchical unloaded and Pd-loaded SnO₂ nanostructures, consisting of many aggregative nanorods were prepared by one-step hydrothermal method. A possible formation mechanism of these hierarchical structures was proposed. The butanone sensing properties of the sensors based on unloaded and hierarchical Pd-loaded SnO₂ nanorods were investigated. The results indicate that the response of sensor using hierarchical Pd-loaded SnO₂ nanorods to 1000 ppm butanone was 451 at 250 °C, which was about 10 times higher than that of sensor based on unloaded SnO₂. Such enhanced gas sensing performances can be attributed to both the chemical and the electrical contribution of Pd loading.     

Development of an optical hydrogen sulphide sensor

A hydrogen sulphide (H₂S)-sensitive optode film has been fabricated by immobilising tetraoctylammonium fluorescein mercury(II) acetate (TOFMA) and tri-n-butyl phosphate in a poly(vinyl chloride) (PVC) matrix. The optode film, coated on an overhead transparency film, was employed as a sensing device for fluorimetric detection of H₂S. The fluorescence intensity monitored at 553 nm (excitation at 503 nm) increased with increasing H₂S concentrations. The optode film showed a good, linear and reversible response to H₂S from 0 to 15 ppm (v/v). It was optically stable and the reproducible response of the film on exposure to 10 ppm (v/v) H₂S was extremely good. There was no sign of degradation after 8 h of continuous use. The response to H₂S levelled off at about 27.5 ppm The response and recovery times of the optical H₂S sensor were fast and less than 2 and 5 s, respectively. An optically-based sensor for H₂S determination was successfully developed. It was anticipated that the system could be used to monitor H₂S with a concentration range of 0–25 ppm (v/v) with satisfactory results. A proposed mechanism for the detection of H₂S by the optode films is described.     

A new optical sensing reaction for nitric oxide

Based on the reaction between the Cu(II) complex of Eriochrome cyanine R (ECR) and nitric oxide (NO) in phosphate buffer (pH 7.4), a new colorimetric method for the determination of NO concentration has been developed. The linear calibration range for NO was 0–60 μM with a detection limit of 1.24 μM. This reaction was then used as the basis in the development of a fibre optic chemical sensor for NO gas. The copper complex was incorporated into silicone rubber membranes and exposed to NO gas after incubating the films in phosphate buffer (pH 7.4). A linear calibration for NO gas between 0 and 6 ppm was obtained with a detection limit of 0.227 ppm (1 μM 0.031 ppm NO in solution). The sensor response was shown to be reproducible and reversible (2.77%, R.S.D., n=4) upon exposure to aqueous phosphate buffer (pH 7.4). The sensor response was also found to be pH independent between 7 and 10.     

Surface acoustic wave gas monitor for ppm ammonia detection

A shear horizontal surface acoustic wave (SH-SAW) sensor coated with polyaniline (PANI) film was investigated in this study. The frequency shift of SH-SAW was measured to detect the presence of ammonia. In addition, an analysis of humidity interference with the ammonia was performed. The SH-SAW sensor in this study responded to the ammonia gas and could be recovered using dry nitrogen. Detecting at an ammonia concentration of 20.45 ppm, the frequency shift was 1.79 ppm and the signal-to-noise ratio was 25.06 dB. This sensor had a response time of less than 150 s. Also, the frequency shift increased as the humidity increased. The cross-sensitivity varied nonlinearly with the ammonia concentration.     

A novel highly sensitive gas ionization sensor for ammonia detection

A novel highly sensitive gas ionization sensor for ammonia detection in ambient air is introduced in this paper. Carbon nanotubes (CNTs) grown on silicon substrate were incorporated to fabricate a gas ionization sensor. Application of a positive bias to the CNTs generates electric fields sufficiently to field-ionize passing gas-phase molecular and initiate a prebreakdown current. When the CNTs film is configured as the cathode, secondary electrons repelled away from the CNTs tips into the gap spacing make more ionizing collisions and also initiate a prebreakdown current. By monitoring the prebreakdown current, the gas ionization sensor was demonstrated to be capable of ionizing and detecting the ammonia and with a linear response over the entire range from 1 to 160 ppm ammonia in air. The sensitivity mechanism of the gas ionization sensor was also discussed in detail. The sensitivity and selectivity of the gas ionization sensor to the gases is not only dependent on its ionization energy but also its electric dipole moment. The novel CNTs-based gas ionization sensor described here exhibits high accuracy, repeatability and stability. The sensor is promising for use in various fields.     

A sensor array optimization method for electronic noses with sub-arrays

Sensor array configuration needs to be optimized in developing an application-specific instrument of electronic noses. Currently, sensor array optimization is commonly done by feature selection techniques. These methods could solve how to optimize a sensor array. However, they could not figure out what are the unique functions that each sensor plays in the optimized sensor array. The method proposed in this paper could solve this problem by sensor clustering and dividing the whole sample classification mission into several small recognition tasks. A measurement with a six Taguchi Gas Sensors (TGS sensor hereinafter) sensors array to classify 11 gas sorts was used in the data validation. The sensor array was optimized to three sensors with the proposed method. Each sensor in the optimized array had unique functions to solve different recognition tasks. TGS2600 had the unique functions to discriminate butanone and acetaldehyde. TGS2602 had the unique functions to discriminate benzene and cyclohexane, methanol and ethanol. TGS813 had the unique functions to discriminate cyclohexane and pentane. The combination of TGS2600 and TGS2602 had the unique functions to discriminate acetone and butanone, acetone and acetaldehyde. The proposed method might be a new generation of sensor array optimization methods.     

On-board phthalocyanine gas sensor microsystem dedicated to the monitoring of oxidizing gases level in passenger compartments

The monitoring of in-vehicle pollutant concentrations by means of an on-board molecular semiconductor gas sensor microsystem is described in this paper. The main objective is to measure in real time with a high level of accuracy the variations of oxidizing gases concentration in bus passenger compartments to inform travelers or commuters and to evaluate the assessment of bus drivers’ exposure. A self-contained gas sensor microsystem of which the sensitive element is constituted by a thin layer of copper phthalocyanine has been developed, validated at laboratory under controlled experimental conditions and then implemented in a bus of the urban network of Clermont-Ferrand, France. Preliminary in-car measurements realized with commercial analyzers show that nitrogen dioxide is the major oxidizing gas present on urban roads and so is considered as the target gas in this study. Tests realized under artificially polluted atmosphere show the high performances obtained with our microsystem, such as high resolution, low threshold, good reproducibility, satisfying concentration range and real time detection. The calibration curve has been determined at laboratory by experiments made under low NO₂ concentrations in the range of those measured in urban atmosphere. The relation between sensor microsystem response and gas concentration is established with accuracy. The validation of our microsystem is illustrated by measurements realized under real conditions, i.e., in an urban bus. It shows that NO₂ concentration variations are mainly correlated with the nature of roads and that rates of pollutant measured in traffic are always greater than those measured by the nearest stations of the air quality control network.