I
NTRODUCTION
2
December 2000 Rosemount Analytical 748221-L
Model 7D Thermal Conductivity Analyzer
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Rosemount Analytical
Model 7D
Thermal Conductivity
Analyzer
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75%
25%
0%
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1 3
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Rosemount Analytical
Model 7D
Thermal Conductivity
Analyzer
bridge, an electric current flows through the filaments, heating them and thus
increasing their electrical resistance. The heat-dissipation rate for each filament
depends on the thermal conductivity of the surrounding gas.
Initially, with suitable downscale calibration gas flowing through the sample passage
(and also through the reference passage if of the flow-through configuration), the
bridge is balanced. Thereafter, any change in the relative proportions of the
components passing through the sample passage changes the thermal conductivity of
the gas mixture, causing a temperature differential between sample and reference
filaments. The resultant change in filament resistance unbalances the bridge,
applying a signal to the electronic circuitry (Section 1.1.2).
F
IGURE
1-1. M
ODEL
7D F
RONT
P
ANEL
C
ONTROLS
