The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Yasunori Tohjima - One of the best experts on this subject based on the ideXlab platform.
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Observation of atmospheric oxygen/nitrogen ratio aboard a cargo ship using gas chromatography/Thermal Conductivity Detector
Journal of Geophysical Research, 2012Co-Authors: Hiroaki Yamagishi, Yasunori Tohjima, Hitoshi Mukai, Yukihiro Nojiri, Chihiro Miyazaki, Keiichi KatsumataAbstract:[1] Measurements of atmospheric O2/N2 ratio and CO2 concentration have been used to analyze the −ΔO2/ΔCO2 ratio to obtain information on CO2 sources, e.g., anthropogenic or terrestrial biogenic sources (respiration or wildfire). In this study we report on the development of a shipboard system for measuring atmospheric O2/N2 ratio by using the gas chromatography/Thermal Conductivity Detector (GC/TCD) technique. The standard error for a one hour average (N = 6) is found to be ± 5 per meg (±1 ppm). The shipboard measurements have been conducted since the end of September 2007 on the Voluntary Observing Ship TRANS FUTURE 5, a cargo ship sailing between Japan, Australia, and New Zealand every six weeks. Spatially, the observation covers latitudes between 41°S and 33°N over the western Pacific. Air masses with high CO2 concentration are observed along the coastline of Australia and New Zealand. In more than two thirds of the cases (17 of 23 events) detected between September 2007 and July 2009, values of the −ΔO2/ΔCO2 ratio are less than 1.15, indicating dominance of biogenic sources (e.g., respiration or wildfire) of CO2.
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observation of atmospheric oxygen nitrogen ratio aboard a cargo ship using gas chromatography Thermal Conductivity Detector
Journal of Geophysical Research, 2012Co-Authors: Hiroaki Yamagishi, Yasunori Tohjima, Hitoshi Mukai, Yukihiro Nojiri, Chihiro Miyazaki, Keiichi KatsumataAbstract:[1] Measurements of atmospheric O2/N2 ratio and CO2 concentration have been used to analyze the −ΔO2/ΔCO2 ratio to obtain information on CO2 sources, e.g., anthropogenic or terrestrial biogenic sources (respiration or wildfire). In this study we report on the development of a shipboard system for measuring atmospheric O2/N2 ratio by using the gas chromatography/Thermal Conductivity Detector (GC/TCD) technique. The standard error for a one hour average (N = 6) is found to be ± 5 per meg (±1 ppm). The shipboard measurements have been conducted since the end of September 2007 on the Voluntary Observing Ship TRANS FUTURE 5, a cargo ship sailing between Japan, Australia, and New Zealand every six weeks. Spatially, the observation covers latitudes between 41°S and 33°N over the western Pacific. Air masses with high CO2 concentration are observed along the coastline of Australia and New Zealand. In more than two thirds of the cases (17 of 23 events) detected between September 2007 and July 2009, values of the −ΔO2/ΔCO2 ratio are less than 1.15, indicating dominance of biogenic sources (e.g., respiration or wildfire) of CO2.
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method for measuring changes in the atmospheric o2 n2 ratio by a gas chromatograph equipped with a Thermal Conductivity Detector
Journal of Geophysical Research, 2000Co-Authors: Yasunori TohjimaAbstract:We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a Thermal Conductivity Detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03′N, longitude 123°49′) from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.
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Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a Thermal Conductivity Detector
Journal of Geophysical Research, 2000Co-Authors: Yasunori TohjimaAbstract:We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a Thermal Conductivity Detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03′N, longitude 123°49′) from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.
Reinoud F. Wolffenbuttel - One of the best experts on this subject based on the ideXlab platform.
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Microstructure for Thermal Impedance Spectroscopy for Biofuel Composition Measurement
MDPI AG, 2017Co-Authors: Bo Jiang, Mohammadamir Ghaderi, Andre Bossche, Jaco H. Visser, Reinoud F. WolffenbuttelAbstract:Thermal impedance spectroscopy has been investigated as a non-destructive technique to determine the composition of ternary mixtures of biofuels. The principle of the Thermal Conductivity Detector has been extended for measuring both the Thermal Conductivity and the Thermal capacity of biofuel in the range between 1 to 100 Hz, using an AC-operated polysilicon heater for injecting a sinusoidal heat flux, and another polysilicon strip at a well-defined spacing or thermopile sensors for measuring the in-phase and quadrature components of the resulting AC temperature difference
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Micro Thermal Conductivity Detector with flow compensation using a dual MEMS device
Sensors and Actuators A-physical, 2016Co-Authors: G. De Graaf, M. Ghaderi, A. Abarca Prouza, Reinoud F. WolffenbuttelAbstract:Abstract A generic method to reduce the in-line flow dependence of Thermal Conductivity Detectors (TCDs) is presented. The principle is based on a dual-MEMS device configuration. Two thin-film sensors on membranes in parallel in the gas stream on the same chip are differentially operated. Both micro-TCDs are designed to be identical in terms of contact with the main gas flow, however a different depth of the detection chamber results in a different response to the Thermal Conductivity of the sample gas. Static and dynamic simulations have been performed to characterize the design of the fabricated structures. Devices have been fabricated in a MEMS process using a combined surface- and bulk micromachining process. The devices have been characterized statically and dynamically. Measurements on prototypes show that depending on the range of gases, device size and flow range device the effect of flow on the Thermal Conductivity can be reduced by a factor 4–15.
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A MEMS Flow Compensated Thermal Conductivity Detector for Gas Sensing
Procedia Engineering, 2015Co-Authors: G. De Graaf, A. Abarca, M. Ghaderi, Reinoud F. WolffenbuttelAbstract:Abstract A novel dual-Thermal Conductivity Detector (TCD) is presented for in-line flow compensation. TCDs generally demonstrate a flow dependence requiring calibration at a fixed flow rate. This dual-TCD is composed of two thin-film sensors on membranes in parallel on the same chip that are differentially operated. Both are laterally identical, but with a difference in quasi-static Thermal Conductivity by a different sample chamber. A reduced flow rate dependence is possible under conditions described in this work. Simulations of the dual-TCD that verify its operation are presented. The device is fabricated using both bulk and surface micromachining. Currently, prototypes are being fabricated and measurements results are forthcoming.
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Flow compensation in a MEMS dual-Thermal Conductivity Detector for hydrogen sensing in natural gas
Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), 2015 Transducers - 2015 18th International Conference on, 2015Co-Authors: G. De Graaf, A. Abarca Prouza, Reinoud F. WolffenbuttelAbstract:Conventional Thermal Conductivity Detectors (TCDs) demonstrate a flow dependence. The approach presented here to reduce the flow dependence is based on the on-line flow compensation using two thin-film sensors on membranes in parallel on the same chip that are differentially operated. These are laterally identically, but with a different depth of the detection chamber, resulting in different quasi-static sensitivities to the Thermal Conductivity of the sample gas. The effects of conduction and convection in the structure have been studied using COMSOL Multiphysics. First prototypes have been fabricated and are presently tested.
Gian Carlo Cardinali - One of the best experts on this subject based on the ideXlab platform.
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Thermal Conductivity Detector for Gas Chromatography: Very Wide Gain Range Acquisition System and Experimental Measurements
IEEE Transactions on Instrumentation and Measurement, 2013Co-Authors: Fabio Rastrello, Pisana Placidi, Andrea Scorzoni, Ivan Elmi, Stefano Zampolli, Enrico Cozzani, Marco Messina, Gian Carlo CardinaliAbstract:The aim of this paper is to present an acquisition system featuring a very wide gain range and experimental measurements of a new micromachined Thermal Conductivity Detector (μ TCD), applied downstream of a gas-chromatography (GC) system. We describe a simple and innovative electronics for μTCD control and data acquisition, outlining its resistance control, native imbalance compensation, and automatic gain control (AGC) algorithm. The acquisition electronics features two parallel amplification stages with programmable gain: a high-gain stage (gain: 70-1280) and a low-gain or attenuating stage (gain: 0.6-30). The resulting detection range turns out to be very wide, with full scales ranging between 3.9 mV and 6.5 V while voltage is acquired with a 10-b-resolution analog-to-digital converter. Measurements and sensitivity tests have been carried out by connecting our μTCD and acquisition system downstream of the microfluidic section and GC column of a commercial GC system. Sensitivity measurements on several toluene masses gave very good results, having observed a system sensitivity of 15.2 ±0.6 μVs/ng. This high sensitivity will enable the μTCD to be used in many portable applications like in-line quality control, and industrial security and safety. We also show the good operation of the AGC algorithm.
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Thermal Conductivity Detector compact Spice model based on experimental measurements and 3D simulations
Sensors and Actuators A-physical, 2012Co-Authors: F. Rastrello, Pisana Placidi, Andrea Scorzoni, E. Cozzani, M. Messina, Ivan Elmi, Stefano Zampolli, Gian Carlo CardinaliAbstract:Abstract In this paper a novel compact Spice model of a Thermal Conductivity Detector (TCD) is presented and validated against an extensive experimental characterization and 3D simulations. The TCD used is based on the ultra low power (ULP) technology and it has been electrically characterized with different helium and nitrogen gas flow rates, via a microfluidic experimental setup. Extraction of global electro-Thermal parameters, exploited for the development of the Spice model, has been performed by using both 3D electro-Thermal FEM simulations made with COMSOL Multyphisics® and experimental measurements. The first result we discuss is the good agreement between 3D FEM simulations of the device, made with COMSOL Multiphysics®, and the experiments, with a maximum error of 2.9% for He flow rate of 9 sccm and around 1.8% for the N2 carrier gas at each considered flow rate. We have demonstrated that the Spice model can reproduce very well the FEM simulations for all the gas flow rates and the operating power values taken into consideration, using simulation parameters extracted from FEM data itself. Results of the Spice model compare well also with the real behavior of a TCD device for both the used gases, using parameters either extracted from FEM simulations or calibrated with experimental measurements, with a maximum error of 0.9% for the He flow rate of 0.29 sccm and a maximum error of 0.8% for the N2 flow rate of 10.3 sccm. The novelty of the proposed approach is to provide a useful instrument for the electronic designer who wants to incorporate a Spice electro-Thermal model in a simulation environment. The TCD can initially be simulated with an electro-Thermal FEM model for a reduced number of operating conditions, then the Spice model can be calibrated and exploited for the electronic design. After device production, the Spice model can eventually be optimized using the experimental results, thus improving the accuracy of the whole electronic circuit simulation.
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Measurements, FEM simulation and spice modeling of a Thermal Conductivity Detector
2011 IEEE International Instrumentation and Measurement Technology Conference, 2011Co-Authors: F. Rastrello, Pisana Placidi, Andrea Scorzoni, E. Cozzani, M. Messina, Ivan Elmi, Stefano Zampolli, Gian Carlo CardinaliAbstract:In this paper we present a micromachined Thermal Conductivity Detector (TCD), based on the Ultra Low Power (ULP) technology. The device has been electrically characterized with different Helium gas flows, via a microfluidic experimental setup. Extraction of global thermo-electric parameters, exploited for the development of an electro-Thermal Spice model, has been performed directly from the experimental measurements and from 3-D electro-Thermal FEM simulations of the device. The resulting Spice model agrees very well with the measurements, with a maximum error less than 0.22%.
Keiichi Katsumata - One of the best experts on this subject based on the ideXlab platform.
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Observation of atmospheric oxygen/nitrogen ratio aboard a cargo ship using gas chromatography/Thermal Conductivity Detector
Journal of Geophysical Research, 2012Co-Authors: Hiroaki Yamagishi, Yasunori Tohjima, Hitoshi Mukai, Yukihiro Nojiri, Chihiro Miyazaki, Keiichi KatsumataAbstract:[1] Measurements of atmospheric O2/N2 ratio and CO2 concentration have been used to analyze the −ΔO2/ΔCO2 ratio to obtain information on CO2 sources, e.g., anthropogenic or terrestrial biogenic sources (respiration or wildfire). In this study we report on the development of a shipboard system for measuring atmospheric O2/N2 ratio by using the gas chromatography/Thermal Conductivity Detector (GC/TCD) technique. The standard error for a one hour average (N = 6) is found to be ± 5 per meg (±1 ppm). The shipboard measurements have been conducted since the end of September 2007 on the Voluntary Observing Ship TRANS FUTURE 5, a cargo ship sailing between Japan, Australia, and New Zealand every six weeks. Spatially, the observation covers latitudes between 41°S and 33°N over the western Pacific. Air masses with high CO2 concentration are observed along the coastline of Australia and New Zealand. In more than two thirds of the cases (17 of 23 events) detected between September 2007 and July 2009, values of the −ΔO2/ΔCO2 ratio are less than 1.15, indicating dominance of biogenic sources (e.g., respiration or wildfire) of CO2.
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observation of atmospheric oxygen nitrogen ratio aboard a cargo ship using gas chromatography Thermal Conductivity Detector
Journal of Geophysical Research, 2012Co-Authors: Hiroaki Yamagishi, Yasunori Tohjima, Hitoshi Mukai, Yukihiro Nojiri, Chihiro Miyazaki, Keiichi KatsumataAbstract:[1] Measurements of atmospheric O2/N2 ratio and CO2 concentration have been used to analyze the −ΔO2/ΔCO2 ratio to obtain information on CO2 sources, e.g., anthropogenic or terrestrial biogenic sources (respiration or wildfire). In this study we report on the development of a shipboard system for measuring atmospheric O2/N2 ratio by using the gas chromatography/Thermal Conductivity Detector (GC/TCD) technique. The standard error for a one hour average (N = 6) is found to be ± 5 per meg (±1 ppm). The shipboard measurements have been conducted since the end of September 2007 on the Voluntary Observing Ship TRANS FUTURE 5, a cargo ship sailing between Japan, Australia, and New Zealand every six weeks. Spatially, the observation covers latitudes between 41°S and 33°N over the western Pacific. Air masses with high CO2 concentration are observed along the coastline of Australia and New Zealand. In more than two thirds of the cases (17 of 23 events) detected between September 2007 and July 2009, values of the −ΔO2/ΔCO2 ratio are less than 1.15, indicating dominance of biogenic sources (e.g., respiration or wildfire) of CO2.
F. Rastrello - One of the best experts on this subject based on the ideXlab platform.
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Thermal Conductivity Detector for gas-chromatography: Acquisition system and experimental measurements
2012 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2012Co-Authors: F. Rastrello, E. Cozzani, M. Messina, P. Placidi, A. Scorzoni, I. Elmi, S. Zampolli, G.c. CardinaliAbstract:The aim of this paper is to present an acquisition system and experimental measurements of a new micromachined Thermal Conductivity Detector (μTCD), applied downstream of a gas-chromatography (GC) system. We describe a simple and innovative electronics for sensor control and data acquisition, outlining its resistance control, native imbalance compensation and automatic gain control (AGC) algorithm. Measurements and sensitivity tests have been carried out by connecting our TCD and acquisition system downstream of the microfluidic section and GC column of a commercial GC system. Comparing the results with those of a complete commercial GC system we observed a similar response and noise. Sensitivity measurements on toluene masses gave very good results, having observed a sensitivity of 15.2±0.6 μVs/ng. This high sensitivity will enable the use of the μTCD in many portable applications like in-line quality control, industrial security and safety. We also show the good operation of the AGC algorithm.
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Thermal Conductivity Detector compact Spice model based on experimental measurements and 3D simulations
Sensors and Actuators A-physical, 2012Co-Authors: F. Rastrello, Pisana Placidi, Andrea Scorzoni, E. Cozzani, M. Messina, Ivan Elmi, Stefano Zampolli, Gian Carlo CardinaliAbstract:Abstract In this paper a novel compact Spice model of a Thermal Conductivity Detector (TCD) is presented and validated against an extensive experimental characterization and 3D simulations. The TCD used is based on the ultra low power (ULP) technology and it has been electrically characterized with different helium and nitrogen gas flow rates, via a microfluidic experimental setup. Extraction of global electro-Thermal parameters, exploited for the development of the Spice model, has been performed by using both 3D electro-Thermal FEM simulations made with COMSOL Multyphisics® and experimental measurements. The first result we discuss is the good agreement between 3D FEM simulations of the device, made with COMSOL Multiphysics®, and the experiments, with a maximum error of 2.9% for He flow rate of 9 sccm and around 1.8% for the N2 carrier gas at each considered flow rate. We have demonstrated that the Spice model can reproduce very well the FEM simulations for all the gas flow rates and the operating power values taken into consideration, using simulation parameters extracted from FEM data itself. Results of the Spice model compare well also with the real behavior of a TCD device for both the used gases, using parameters either extracted from FEM simulations or calibrated with experimental measurements, with a maximum error of 0.9% for the He flow rate of 0.29 sccm and a maximum error of 0.8% for the N2 flow rate of 10.3 sccm. The novelty of the proposed approach is to provide a useful instrument for the electronic designer who wants to incorporate a Spice electro-Thermal model in a simulation environment. The TCD can initially be simulated with an electro-Thermal FEM model for a reduced number of operating conditions, then the Spice model can be calibrated and exploited for the electronic design. After device production, the Spice model can eventually be optimized using the experimental results, thus improving the accuracy of the whole electronic circuit simulation.
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Measurements, FEM simulation and spice modeling of a Thermal Conductivity Detector
2011 IEEE International Instrumentation and Measurement Technology Conference, 2011Co-Authors: F. Rastrello, Pisana Placidi, Andrea Scorzoni, E. Cozzani, M. Messina, Ivan Elmi, Stefano Zampolli, Gian Carlo CardinaliAbstract:In this paper we present a micromachined Thermal Conductivity Detector (TCD), based on the Ultra Low Power (ULP) technology. The device has been electrically characterized with different Helium gas flows, via a microfluidic experimental setup. Extraction of global thermo-electric parameters, exploited for the development of an electro-Thermal Spice model, has been performed directly from the experimental measurements and from 3-D electro-Thermal FEM simulations of the device. The resulting Spice model agrees very well with the measurements, with a maximum error less than 0.22%.