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3.
INSTRUMENT PROTECTION
3.1 CABLE SPLICING AND TERMINATION
Terminal boxes with sealed cable entries are available from
for all types
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of applications. These allow many instruments to be terminated at one location
with complete protection of the lead wires. The interior panel of the terminal box
can have built-in jacks or a single connection with a rotary position selector
switch. Contact
for specific application information.
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Because the vibrating wire output signal is a frequency rather than a current or
voltage, variations in cable resistance have little effect on instrument readings;
therefore, splicing of cables has no ill effects, and in some cases may in fact be
beneficial. The cable used for making splices should be a high quality twisted
pair type, with 100% shielding and an integral shield drain wire. When splicing,
it is very important that the shield drain wires be spliced together.
Always maintain polarity by connecting color to color.
Splice kits recommended by
incorporate casts that are placed around
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the splice and are then filled with epoxy to waterproof the connections. When
properly made, this type of splice is equal or superior to the cable in strength
and electrical properties. Contact
for splicing materials and additional
GEOKON
cable splicing instructions.
Terminate a cable by stripping and tinning the individual conductors and then
connecting them to the patch cord of a readout box. Alternatively, use a
connector to plug directly into the readout box or to a receptacle on a special
patch cord.
3.2 PROTECTION FROM MECHANICAL DAMAGE
The cover of the 4100 coil housing provides a measure of protection for the
strain gauge, which is adequate in most cases. In extreme environments and/or
where long term performance is required, gauge and lead wires may require
additional protection from corrosion and mechanical damage.
3.2.1 SECURING CABLES
Cables should be adequately restrained so that there is no danger of the coil
housing being damaged (Model 4100) or the lead wires torn out (Model 4150) by
tugging on the cable. Cables may be secured using pieces of stainless steel shim
strips (supplied), spot welded in place over the top of the cable. Tie wraps, tape,
or wire ties may also be used to secure the gauge cables.
3.2.2 COVER PLATES
Gauges can be further protected by welding cover plates composed of 101 x 38
mm (4" x 1.5") channel iron or 64 mm (2.5") or larger angle iron over the top of
the gauges.
To avoid damaging the cables, the protection should be welded on before the
gauges and cables are installed. To accomplish this, leave windows in the steel
over the gauge locations.
Note: It is not necessary to use continuous welds; tack welding is sufficient as
long as it holds the angles or channels firmly in place. Cables must be restrained
using welding studs, to which the cables can be tied at three-meter intervals.
4 | INSTRUMENT PROTECTION | GEOKON
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