LI-COR LI-7815, Instruction Manual

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Plumbing a subsample
Note: We are currently refining numerous sampling protocols for the LI-7815.
Contact LI-COR technical support (envsupport@licor.com) if you have questions
about your application.
A typical sampling application will use the LI-7815 to subsample a gas from a main
sample line. Air passes a single time through the gas analyzer before it is discharged.
Air supplied to the sample inlet should be between ambient and 35 kPa (5 PSI)
above ambient. If the pressure is higher than that, install a 30 cm vent in the sample
line to ensure that air from the external pump does not pressurize the analyzer. The
vent must be sufficiently long to prevent diffusion of ambient air into the sample air
supply.
Figure 3-3. A basic open system, where air is supplied to the gas analyzer by an external
pump. If the pressure exceeds 35 kPa above ambient, install a 30 cm vent in the air supply
line. Attach the inlet to the 'leg' of the T-fitting to avoid isotopic fractioning.
Section 3. Applications of the LI-7815
3-3 Plumbing a subsample