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Theory of Operation
As seen in table 2-1, CO
conductivity over the stated temperature range. This would result in
unacceptable accuracy if the temperature of the gas were not controlled
during analysis. Simply compensating for the temperature change is not
sufficient unless the temperature fluctuation is extremely small.
When measuring the thermal conductivity in a mixture of gases,
best performance is realized when there is a large T/C difference
between the gases. For example, it is relatively straightforward to
determine the concentration of hydrogen in air at 26.7°C based on T/C
measurements since the relative difference in thermal conductivities is
great—446.32 (H
) and 62.2 (air). However it becomes difficult or
2
impossible to distinguish nitrogen (64.4) in air (62.2) at the same
temperature using only the difference in thermal conductivities, as they
are so close to each other.
Thermal conductivity analyzers are not gas specific, they monitor
the change in the thermal conductivity of a gas mixture. The sensor itself
has no way of knowing whether the mixture is hydrogen in air or
hydrogen in CO
, it only knows what the thermal conductivity of the gas
2
mixture is. A reading of 60% would be meaningless unless the
components of the gas are known, the analysis range is known, and the
instrument is properly calibrated for that mixture on that range.
The Model 2750 Turbine Generator Gas Analyzer is designed for
analyzing the following binary gas mixtures and ranges:
0-100% hydrogen in CO
0-100% air in CO
80-100% hydrogen in air
This instrument should not be used for any other gas mixtures or
ranges different from above unless you have thoroughly examined the
gas mixture in question and have determined that it is equivalent to one
of the installed ranges. This instrument uses pre-programmed data for
linearization purposes which, in general, would not apply to another
mixture.
CAUTION:
MEASURING HYDROGEN IN AIR BETWEEN THE
RANGES OF 4% TO 74.2% HYDROGEN IS
COMBUSTIBLE AND SHOULD BE AVOIDED FOR
SAFETY REASONS.
Teledyne Analytical Instruments
has over 10% change in its thermal
2
2
2
Model 2750
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