Method and apparatus for the measurement of the thermal conductivity of gases
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United States of America Patent
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Jan 21, 1992
Issued Date -
N/A
app pub date -
Dec 11, 1989
filing date -
Feb 6, 1989
priority date (Note) -
Expired
status (Latency Note)
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Abstract
New methods and apparatus for the measurement of thermal conductivity of gases employ a single katharometer element comprising a thermistor. In one circuit the thermistor is part of a first potential divider whose output voltage is compared to that of a second reference potential divider by applying them to the inputs of a differential amplifier supplying heating current to the element. In another circuit, in which the katharometer element may be other than a thermistor, the element and a resistor are connected in series to a common reference point of the circuit and are supplied with current so that the voltages across them correspond to their respective resistances; the voltage cross the item not connected to the reference point is transferred to another circuit element that is connected to the reference point so that they can be compared directly. If the temperature of the element changes, changing its resistance, the amplifier output changes the amount of power supplied to the katharometer element to restore it to the predetermined temperature. Passage of a gas with a different thermal characteristic over the element changes its temperature, which is corrected by the circuit so that the element operates at a constant temperature.
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