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OPERATION
An inadequate flow rate can:
•
Accentuate adsorption and desorption effects on the gas passing through
the sampling system.
•
Allow pockets of wet gas to remain undisturbed in a complex sampling
system, which will then gradually be released into the sample flow.
•
Increase the chance of contamination from back diffusion: ambient air that
is wetter than the sample can flow from the exhaust back into the system.
A longer exhaust (sometimes called a pigtail) can also help alleviate this
problem.
•
Slow the response of the sensor to changes in moisture content.
An excessively high flow rate can:
•
Introduce back pressure, causing slower response times and unpredictable
effects on equipment such as humidity generators.
•
Result in a reduction in depression capabilities in chilled mirror instruments
by having a cooling effect on the mirror. This is most apparent with gases
that have a high thermal conductivity such as hydrogen and helium.
28
Optisure Remote User's Manual
POSSIBLE INJURY! The tubing, valves and other
apparatus attached to this instrument must be
adequate for the maximum pressure which will be
applied, otherwise physical injury to the operator or
bystander is possible.
Before disconnecting the instrument from the gas
line it is essential to vent the system to atmospheric
pressure, otherwise severe injury could result.
March 2018
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