Teledyne 238 - Thermal conductivity analyzer - Manual (Page 5)

1-1 Teledyne Analytical Instruments
Thermal Conductivity Analyzer Introduction 1
Introduction (Models 235, 236, 237, 238)
The 235 Series Thermal Conductivity Analyzers measure the concen-
tration of one component in a binary stream of gas, or the purity of a sample
stream containing a composite mixture of impurities, by comparing the
difference in thermal conductivity of the sample stream with that of a
reference gas of fixed composition.
Control of the sample and supporting gases is not provided for in the
basic design TAI offers a variety of supporting gas control panels as com-
panion accessories to the analyzer to fill this need. In any case, means must
be provided for controlling the flowrates through the sample and reference
paths of the analyzer, and a control manifold will be required for the intro-
duction of zero and span gas, as well as sample gas, into the sample path.
Appropriate pressure reducing regulators will have to be installed at all gas
supply sources; for those customers wishing to incorporate their own
sample controls, a recommended system piping schematic is included among
the drawings at the rear of the manual.
Thermal conductivity measurements are non-specific by nature. This
fact imposes certain limitations and requirements. If the user intends to
employ the analyzer to detect a specific component in a sample stream, the
sample must be composed of the component of interest and one other gas in
order to be accurate.
If, on the other hand, the user is primarily interested in the purity of a
process stream, and does not require specific identification of the impurity,
the analyzer can be used on more complex mixtures. The impurities, then,
can be a composition in themselves.