Thermal conductivity detector

Details Thermal conductivity detector Thermal conductivity detector

1993-06-28

1995-01-10

Noland, Thomas P.

Measuring and testing

Gas analysis

By thermal property

732025, 7320415, 73 35, 422 96, 324105, 324450, G01N 2518

Patent

active

053796306

ABSTRACT:
In one embodiment, a thermal conductivity detector in a gas chromatograph is provided with a sensor connected in a resistive bridge with an alternating voltage applied to the bridge. Changes in thermal conductivity of a gas in the sensor cause changes in the temperature and resistance of the sensor which unbalances the bridge. A component of the voltage difference caused by the imbalance varies as the third harmonic of the applied voltage and has a magnitude related to the thermal conductivity of the gas. This third harmonic is measured to determine the thermal conductivity of the gas. In another embodiment, a sensor in a cavity through which gas flows is alternately operated at two different temperatures, and a difference in power required for operation is measured. The difference is independent of the temperature of the cavity walls and proportional to the thermal conductivity. This difference is measured to determine the thermal conductivity of the gas.

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Dr. Dietrich Jentzsch and Dipl-Ing. Eginhard Otte, "Detectors in Gas Chromatography: Wheatstone Bridge for AC Operation", Academic Publishing Co, Frankfurt, Germany, 1970, pp. 121-122 and pp. 154-157.

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