Initial Readings; Lightning Protection - Geokon 4450 Instruction Manual

2.5. Initial Readings

Initial readings must be taken and carefully recorded along with the temperature at the time
of installation. These readings serve as a reference for subsequent deformation
calculations.

2.6. Lightning Protection

The Model 4450 Vibrating Wire Displacement Transducers, unlike numerous other types of
instrumentation available from Geokon, do not have any integral lightning protection
components, i.e. transzorbs or plasma surge arrestors. Usually this is not a problem
however, 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 gage and
possibly destroy it.
Note the following suggestions;

If the gage is connected to a terminal box or multiplexer components such as plasma
surge arrestors (spark gaps) may be installed in the terminal box/multiplexer to provide a
measure of transient protection. Terminal boxes and multiplexers available from
Geokon provide locations for installation of these components.

Lighting arrestor boards and enclosures are available from Geokon that install near the
instrument. The enclosure has a removable top so, in the event the protection board
(LAB-3) is damaged, the user may service the components (or replace the board). A
connection is made between this enclosure and earth ground to facilitate the passing of
transients away from the gage. See Figure 2. Consult the factory for additional
information on these or alternate lightning protection schemes.

Plasma surge arrestors can be epoxy potted into the gage cable close to the sensor. A
ground strap would connect the surge arrestor to earth ground, either a grounding stake
or other suitable earth ground such as perhaps the strand to which the transducer is
attached.
Terminal Box/Multiplexer
Instrument Cable
(usually buried)
Ground Connections
Figure 2 - Lightning Protection Scheme
Extensometer
Model 4450 Transducer
(inside extensometer housing)
LAB-3 Enclosure LAB-3 Board
Surface
3