Geokon 4911, Руководство по установке, Страница: 11 / 27

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2.4 Cable Installation
As noted in the in the previous sections, instrument cables should be routed along the structural
rebar and secured with nylon cable ties every two to three feet (one-meter). Outside of the
instrumented structure, the cable should be protected from accidental damage caused by moving
equipment or other construction activity.
2.5 Cable Splicing and Termination
Terminal boxes with sealed cable entries are available from Geokon for all types of applications.
These allow many gauges 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 Geokon for specific application information.
Cables may be terminated by stripping and tinning the individual conductors and then connecting
them to the patch cord of a readout box. Alternatively, a connector may be used which will plug
directly into the readout box or to a receptacle on a special patch cord.
The cable from the strain meters can also be protected by the use of flexible conduit, which can
be supplied by Geokon.
Because the vibrating wire output signal is a frequency rather than a current or voltage,
variations in cable resistance have little effect on gauge 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 Geokon incorporate casts that are placed around 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 Geokon for splicing
materials and additional cable splicing instructions.
2.6 Lightning Protection
Unlike numerous other types of instrumentation available from Geokon, rebar strain meters do
not have any integral lightning protection components, such as transorbs or plasma surge
arrestors. Usually this is not a problem, as these types of gauges are installed within concrete and
are somewhat isolated from potentially damaging electrical transients. However, there may be
occasions where some sort of lightning protection is desirable, for example, where the instrument
is in contact with rebar that is exposed to direct or indirect lightning strikes. In addition, if the
instrument cable is exposed, it may be appropriate to install lightning protection components, as
the transient could travel down the cable to the gauge and possibly destroy it.