2-18
Initial Setup
Important Note on Wire Insertion
When inserting wires through the gland plugs on the Auxiliary Sensor Interface, it is
important that a water-tight seal is formed when the gland plug cap is tightened.
Note that in the picture above at Step 6, the wire leads are encased in a round
sheath, which provides a good seal with the bushing in the gland plug. Bare wires
that are not sheathed do not seal tightly; moisture will travel along the bare wires,
or in the groove of two attached wires, and could blow the fuse in the Auxiliary
Sensor Interface, or cause corrosion to the connector and/or circuit board. If you
are continuously blowing fuses, check to see if the wires are tightly sealed; if not,
you may need to encase bare wires in a short piece of sheathing material.
Using Soil Collars
Both the Survey and Long-Term soil chambers for the LI-8100A require the use of a
soil collar that is inserted (and usually left) in the soil before making measurements.
Using soil chamber collars has several advantages over direct insertion if the
chamber into the soil, including:
The disturbance effect of insertion will not affect measurements conducted
several hours or days later.
It is possible to make repeated measurements at one location.
Construction of Soil Collars
Soil collars for use with the 10 cm (4") survey chamber can be easily constructed
from thin-walled polyvinyl chloride (PVC) pipe. The tubing must have an inside
diameter of 10 cm (3.930”) minimum and an outside diameter of 11.4 cm (4.50")
maximum. Cut a section approximately 8.9 cm (3.5”) long or longer, depending
on your soil type and experiment. Bevel one edge with a grinding wheel so that it
is easier to press into the soil. The 10 cm (4") soil collars are available from LI-COR
under part #6581-157 (1 each).
Soil collars for use with the Long-Term chambers or 20 cm Survey Chamber require
a bit more effort to construct; we use a thick-walled 20.3 cm (8") PVC sewer pipe
(i.e., Schedule SDR35), and a large lathe to bevel the edge. If you have access to a
machine shop and want to try to construct your own 20.3 cm (8") collars, we have
provided the mechanical specifications below. You can bevel the edge as desired,
but keep in mind that a sharper edge will aid in insertion of the collar, particularly
in hard soils. The 20.3 cm (8") soil collars are also available from LI-COR under
part #6581-044 (1 each).
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