A Study of Application of Miniaturized Thermal Conductivity Detector in Gas Concentration Determination

• Main Authors: Keng-hao Hsu, 許耿豪
• Other Authors: Albert Wu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/55719864467471023136

碩士 === 國立臺灣科技大學 === 機械工程系 === 88 === Using micro-fabrication technology, a miniaturized Thermal Conductivity Detector (TCD) for portable gas chromatography (GC) was successfully fabricated on a two-layered silicon chip. This fabricated Micro-TCD has a three-layer microstructure with two microchannels forming the arms of a Wheatstone bridge. Each microchannel consist of two heating elements deposited on a supporting membrane made of Pyrex glass. Photolithography, wet-etching, chip-bonding, packaging and wire-bonding techniques were used to fabricate this miniaturized TCD. In this study, tests were performed to determine and to calibrate the characteristics of this miniaturized TCD, Then, a feasibility study on the application of this Micro-TCD to gas constituent determination was conducted. Experimental results showed that at least 12V of driving voltage is required for the Micro-TCD to produce a stable output voltage. An output voltage around 12.4mV is generated for a 10% concentration change of an Ar-He gas mixture. With driving voltage of 12V, an output voltage around 161mV is obtained for a temperature difference of 10℃. Further increase of heating element resistance is necessary to improve the sensitivity of Micro-TCD in measuring the presence of a gas species and its concentration in highly diluted gas mixture.