6
2.4 Cable Installation and Splicing
The cable should be routed to minimize the possibility of damage due to moving equipment,
debris or other causes. The cable can be protected by the use of flexible conduit, which can be
supplied by Geokon.
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.
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, which 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.
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.
2.5 Initial Readings
All readings are referred to an initial reading so it is important that this initial reading be
carefully taken.
Conditions should be noted at the time of all readings, especially during curing,
e.g., temperature, time after placement, local conditions, etc.
2.6 Electrical Noise
Care should be exercised when installing instrument cables to keep them as far away as possible
from sources of electrical interference such as power lines, generators, motors, transformers, arc
welders, etc.
Cables should never be buried or run with AC power lines!
The instrument
cables will pick up the 50 or 60 Hz (or other frequency) noise from the power cable and this will
likely cause a problem obtaining a stable reading.