Thermal measuring and testing – Determination of inherent thermal property – Thermal conductivity
Patent
1995-10-25
1998-06-30
Dombroske, George M.
Thermal measuring and testing
Determination of inherent thermal property
Thermal conductivity
73 2503, 73 2505, G01N 2518
Patent
active
057723214
ABSTRACT:
A thermal conductivity detector includes a cavity wall defining a cavity for receiving a quantity of a sample fluid, the cavity wall being subject to a cavity wall temperature that is temporally and spatially variable, and a sensor located in the cavity and connected preferably in a bridge circuit configuration for providing a temperature sense signal. The sensor exhibits a resistance which is dependent on a temperature of the sensor. A first signal providing means includes reference means preferably in the form of first and second reference resistors located within first and second reference resistor cavities. The first and second reference resistors are connected to a reference voltage in a voltage divider network such that a node of the voltage divider network provides a temperature compensation signal that is representative of the average temperature of the cavity wall. Second signal providing means, connected to the balance nodes of the bridge circuit configuration, provide a temperature sense signal that is related to a change in resistance of the sensor resistor and thereby representative of the sensor temperature. The temperature compensation signal may optionally be conditioned by a voltage gain circuit and a voltage offset circuit to provide a temperature compensation signal. The temperature sense signal and the temperature compensation signal are provided to a third signal providing means wherein the temperature compensating signal is used to accurately compensate for changes in the temperature sense signal that are due to the temporal and/or spatial variations in the cavity wall temperature. In particular, the temperature compensation signal may represent an averaged value of at least two cavity wall temperatures, thus particularly compensating for the effect of a spatial temperature gradient in the cavity wall.
REFERENCES:
patent: 4389876 (1983-06-01), Szonntagh
patent: 4902138 (1990-02-01), Goeldner et al.
patent: 5379630 (1995-01-01), Lacey
UK Patent Office, Dec. 6, 1996, Examiner: Clarke, M.G.
Dombroske George M.
Dudley Mark Z.
Felber Joseph L.
Hewlett--Packard Company
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