EP0724151A1
Expired / Lapsed
EP
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Thermal conductivity measuring device
Assignee: Azbil Corp
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Filing: 1996-01-11
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Granted: —
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Expires: 2016-01-11
Abstract
Abstract A thermal conductivity measuring device includes a diaphragm portion, a thermal conductivity detector, a temperature sensor, a control section, and a thermal conductivity calculating section. The diaphragm portion is formed on a base. The thermal conductivity detector is formed in the diaphragm portion to perform conduction of heat to/from a sample gas. The temperature sensor is disposed on the base to be near the thermal conductivity detector so as to measure the ambient temperature around the base. The temperature sensor is thermally insulated from the thermal conductivity detector. The control section controls the amount of energy supplied to the thermal conductivity detector such that the temperature difference between the ambient temperature measured by the temperature sensor and the heating temperature of the thermal conductivity detector becomes a constant value. The thermal conductivity calculating section calculates the thermal conductivity of the sample gas on the basis of the amount of energy supplied to the thermal conductivity detector while the temperature difference is kept at the constant value by the control section.
Inventors
- 👤 Hiroyuki c/o Kamata Factory Muto
- 👤 Yasuhiro c/o Kamata Factory Kajio
- 👤 Shoji c/o Fujisawa Factory Kamiunten
- 👤 Mitsuhiko c/o Fujisawa Factory Nagata
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 07:40
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/14; G01N27/18; G01N27/185
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
148 words
A thermal conductivity measuring device characterized by comprising: a diaphragm portion (31) formed on a base (30); heating means (21), formed in said diaphragm portion, for performing conduction of heat to/from a sample gas; measuring means (22), disposed on said base to be near said heating means, for measuring an ambient temperature around said base, said measuring means being thermally insulated from said heating means; control means (23, 29) for controlling an amount of energy supplied to said heating means such that a temperature difference between the ambient temperature measured by said measuring means and a heating temperature of said heating means becomes a constant value; and thermal conductivity calculating means (24) for calculating a thermal conductivity of the sample gas on the basis of the amount of energy supplied to said heating means while the temperature difference is kept at the constant value by said control means.
Claim 2
Dependent Claim
53 words
A device according to claim 1, wherein said control means comprises: first control means (29) for keeping the ambient temperature measured by said measuring means at a constant value; and second control means for keeping the heating temperature of said heating means at a constant value by controlling the amount of energy supplied.
Claim 3
Dependent Claim
65 words
A device according to claim 1, wherein said thermal conductivity calculating means calculates a thermal conductivity λm of the sample gas from an output voltage v generated across two ends of said heating means according to the following mathematical expression: λm = (v 2 /Rh - B)/A where Rh is a resistance value of said heating means, and A and B are intrinsic device constants.
Claim 4
Dependent Claim
49 words
A device according to claim 3, wherein the device constants A and B in the mathematical expression used in said thermal conductivity calculating means are set on the basis of output voltages measured by supplying first and second calibration gases, whose thermal conductivities are known, to said heating means.
Claim 5
Dependent Claim
65 words
A device according to claim 1, wherein when an output voltage generated across two ends of said heating means and a resistance value of said heating means are respectively represented by v and Rh, said thermal conductivity calculating means obtains a thermal conductivity λm of the sample gas, which corresponds to the output voltage v in accordance with an intrinsic v-λm characteristic stored in advance.
Claim 6
Dependent Claim
43 words
A device according to claim 1, wherein an average value of the ambient temperature kept at a constant value by said first control means and the heating temperature kept at a constant value by said second control means is set to be 100°C.
Claim 7
Dependent Claim
40 words
A device according to claim 1, wherein said heating means comprises a heating resistive element, and said second control means controls a calorific value by changing an applied voltage as an amount of energy supplied to said heating resistive element.
Claim 8
Dependent Claim
62 words
A device according to claim 7, wherein said second control means comprises a resistance bridge (20) including said heating resistive element, and a comparator (23) for comparing voltages generated at first and second resistor connection points of said resistance bridge which oppose each other, and applying a voltage corresponding to the comparison result to another resistor connection point of said resistance bridge.
Claim 9
Dependent Claim
77 words
A device according to claim 8, wherein a temperature sensor constituting said measuring means is connected to one side, to which said heating resistive element is not connected, of the first and second resistor connection points, and a current flowed to said heating resistive element is controlled such that a temperature difference between the heating temperature of said heating resistive element and the ambient temperature around said base which is measured by said temperature sensor becomes constant.
Claim 10
Dependent Claim
37 words
A device according to claim 1, further comprising a thermostat tank (27) for storing said base on which said heating means and said ambient temperature measuring means are mounted, and holding temperatures thereof at a constant temperature.
Claim 11
Dependent Claim
88 words
A device according to claim 1, further comprising: memory means (26) storing a calibration curve determined in accordance with types of a measurement gas contained in the sample gas; and concentration output means (25) for outputting a concentration of the measurement gas contained in the sample gas on the basis of the thermal conductivity of the sample gas which is calculated by said thermal conductivity calculating means by referring to the calibration curve read out from said memory means in accordance with a composition of the sample gas.
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