3.6 Valves
The analyzer contains two valves, a needle valve flow control, and a
unique 4-way valve that either seals the sensor, allowing the sample
gas to bypass it, or else allows the sample to flow into the sensor. The
needle valve is mounted in the middle of the Sample/Bypass valve,
and is designed so that the flow is the same no matter which position
the Sample/Bypass valve is in .
Trace oxygen sensors are of course very sensitive, and so it is
desirable that they not be exposed to air(which has a very high oxygen
content)more than necessary. If a sensor is exposed to air for more
than a minute or so, its electrolyte will become saturated, and it will
take a long time for the internal chemistry to reduce all of the
dissolved oxygen. During this time the sensor will read high, and not
be able to measure low oxygen levels. The arrangement of valves in
this analyzer avoids this problem, without requiring any great skill on
the part of the operator. The result is that that analyzer can be taken
from sampling point to point and immediately used, without having to
wait for excess oxygen to be used up.
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