自动进样与恒温控制型电子舌检测系统

Electronic Tongue Detection System with Automatic Sampling and Constant Temperature Control

针对现有电子舌集成化、自动化程度较低的问题,设计了一台能自动调节样品温度、进样、清洗电极和检测样品的伏安型电子舌,包括上位机、控制模块、电极与信号采集模块、自动进样模块、恒温槽模块和按键显示模块。系统的控制界面基于Lab VIEW设计开发,通过串口向控制模块发送指令,进而控制自动进样、恒温槽等模块协同工作。电极与信号采集模块采用了三电极检测体系,由贵金属裸电极阵列、调理电路、采集卡构成,运用脉冲伏安法获得样品的信号曲线,并与上位机之间通过USB互传数据。对设备的进样和调温性能试验结果表明,自动进样模块能可靠运行,恒温槽对样品的温度控制范围为(25±1)℃。对设备的检测性能试验表明,检测信号特征值随时间漂移较小,有良好的稳定性。样品温度波动会引起特征值显著变化,恒温槽控温能有效提高电子舌检测精度。使用电子舌对不同类型的啤酒、牛奶、水和不同等级的茶叶4大类样品进行检测,对数据运用主成分分析(PCA),结果显示电子舌对它们均能有效区分。

The electronic tongue has better stability and repeatability than sensory evaluation and it also has the advantages of easy-operated and faster detection speed relative to traditional equipments. At present,the research of electronic tongue is mainly focused on sensor development,and the research on system integration and automation is rare. Thus,a voltammetric electronic tongue was designed,which can automatically adjust the temperature of sample,feed into sample,clean the electrode and detect sample. It included the upper computer,control module,electrode,signal acquisition module,automatic sampling module,thermostatic bath module and display module,etc. The control interface was based on Lab VIEW. The upper computer sent commands to control module to drive the automatic sampling module,thermostatic bath module and other modules through the serial port. Signal acquisition module connected the upper computer through USB cable. It contained a three electrodes system,and the signal curve of the sample was obtained by pulse voltammetry. The test results showed that all the modules were stable and reliable and the temperature control accuracy of the sample was（ 25 ± 1） ℃. The area between the signal curve and the X axis was used as the signal characteristic value. The drift of signal characteristic values of 20 d was below 5. 6%. The characteristic value was affected significantly by the sample temperature. When the sample temperature departure was ± 5℃,the error of the characteristic value was 36%. Under the control of temperature bath（ 25 ± 1） ℃,the error of the characteristic valuewas 5. 8%,which indicated that the temperature control can effectively improve the accuracy of electronic tongue detection result. In the detection application,the electronic tongue can distinguish among four different kinds of beer,milk,water and different grades of tea with the principal component analysis（ PCA）.