LI-COR LI-7820, Instruction Manual

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Section 3. Applications of the LI-7820
Soil gas flux measurements
The LI-7820 works well for soil gas flux measurements when coupled with the LI-
8250 Multiplexer and the Smart Chamber. All hardware, cables, and tubing
required for the connection is available for purchase. The digital communication
connection is established through the LI-8250 or Smart Chamber web interface.
Full details are provided in the LI-8250 and Smart Chamber instruction manuals.
Connecting the air inlet and outlet
Air is drawn into the sample cell through the air inlet. Connect a ¼" outside dia-
meter metal or plastic tube to the air inlet compression fitting. The nut and ferrule
sets are in the accessories kit.
Caution: Be very careful when working near standing water. If water is drawn
into the air inlet, the instrument will have to be repaired at the factory.
Figure 3-2. When connecting a tube to the air inlet, use steel ferrules to form a good seal.
Tighten the nut over the ferrule set until it is finger tight. For metal and plastic
tubing, tighten it an additional 1¼ turns if you are connecting the tube for the first
time. For plastic tube that is highly pliable, insert a stainless steel tube insert (300-
18126) to make the end of the tube rigid. When reconnecting a plastic or metal
tube that has been connected previously, simply tighten it ¼ turn beyond finger
tight. Tubing can be connected to the outlet in the same way.
3-2 LI-7820 N₂O/H₂O Gas Analyzer