Campbell Scientific HydroSense® Soil Water Content System (CS620, CD620) - Manual (Page 18)

HydroSense Soil Water Measurement System (CD620, CS620)
In December 2009, the rods were redesigned (see Figure 8-2).
Rods shipped prior to December 2009 had a disc-shaped collar
instead of a nut. The open-ended wrench is not used with the
older rod design; pliers are used instead. Because of this, the
open-ended wrench began shipping with the CS620 in December
2009. NOTE
FIGURE 8-2. Newer CS620 rod design (left)
and older CS620 rod design (right).
The friction between the nut and the insert surface along with thread friction
will generally provide good rod attachment and loosening is unlikely. If rod
loosening does occur, a thread coating compound can be used to enhance
friction. There are two thread compounds that laboratory testing indicates
minimal effect on the HydroSense measurement.
A package with Loctite ® 222MS THREADLOCKER is included with each
CS620 probe. There is enough thread coating to treat several rods. The
compound should be used sparingly as a thick coating will cause slightly
higher measured water content values.
Another product that works well is Vibra-Tite by ND Industries. This
compound has a higher viscosity than most thread coatings and a narrow strip
is painted on the threads. The applied compound must cure aerobically before
the rods are threaded into the probe inserts. The cured compound is a resilient
plastic which is reusable several times. It is important that the rod threads are
not completely coated because this can affect response of the probe.
Replacement of the rods is a simple matter of screwing the threaded end of
each rod into the insert of the probe body with attention to the following
details.
• Threads should be clean before rod attachment.
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