Vol.2 No.3 2009

Research paper : A marked improvement in the reliability of the measurement of trace moisture in gases (H. Abe)−216−Synthesiology - English edition Vol.2 No.3 (2009) the research and development of measuring instruments to increase the response of sensors based on the adsorption of water molecules, and some sensors have already been commercialized. Increasing the performance and lowering the cost of these sensors are awaited. For the development of other trace moisture analyzers, a specialized Fourier transform infrared spectrometer (FTIR) for trace moisture measurement has been recently developed and marketed, and the appearance of trace moisture analyzers using absorption spectroscopy techniques other than CRDS is also awaited. In this research, only a few of the conventionally used trace moisture analyzers were tested, and there may be high-performance trace moisture analyzers among those not tested in this research. In order to demonstrate the performance of an instrument, regardless of whether it is a new or conventionally used analyzer, the author considers that it is crucial to carry out performance tests (particularly for response, sensitivity, and drift) using a method traceable to the trace moisture standard. Clearly presenting the test results to other users will lead to the dissemination of a highly reliable trace moisture analyzer.All the topics in this paper pertain to the trace moisture measurement in nitrogen, but the demand for trace moisture measurement in gases other than nitrogen is increasing in the semiconductor industry. However, there is no trace moisture standard for other gases at present, and it is necessary to consider this issue.Recently, trace moisture standards have been established in countries other than Japan, and these standards are currently being developed or maintained by individual countries. In general, the equivalence of national standards maintained by different countries is confirmed through an international comparison. A preliminary international comparison has been initiated recently for the trace moisture standard. Four national metrology institutes, namely, the National Metrology Institute of Japan (NMIJ), National Physical Laboratory (NPL) of UK, National Institute of Standards and Technology (NIST) of the USA, and Physikalisch-Technischen Bundesanstalt (PTB) of Germany, are participating in this international comparison, which is now in progress (as of July 2009). The result will be reported separately. Because an international comparison is extremely important for further increasing the reliability of the AIST trace moisture standard and for its recognition by other countries, we plan to participate actively in such endeavors in the future.AcknowledgementsI thank the staff and researchers of NMIJ: Hiroshi Kitano, Chief of Humidity Standards Section; Dr. Chiharu Takahashi (former Head of Temperature and Humidity Division); Masaaki Ueki, Senior Research Scientist; Dr. Shin-ichi Nakao (former Chief of Flow Standards Section); Michito Imae, Head of Time Frequency Division; Dr. Hideyuki Tanaka, Researcher; Dr. Naoki Kuramoto, Researcher; Dr. Nobuhiro Matsumoto, Researcher; and all other people who cooperated and gave us advice on the development of the instrument and the uncertainty evaluation. I am grateful to the technical staff of Rubotherm GmbH, Tiger Optics LLC, K.K. Hirai, DKK-Toa Corporation, Wakana Design Office, Fig. 15 Comparison of standard value and indication of conventional aluminum oxide capacitive sensor.Time / hTime / hTime / hTime / hxw / (nmol·mol-1)Company FCompany ECompany DCompany CStandardIndicationStandardIndicationStandardIndicationStandardIndication5050505000000000100100100150100202020201030404040xw / (nmol·mol-1)xw / (nmol·mol-1)xw / (nmol·mol-1)


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