4. LIGHTNING PROTECTION
The Model 4370 Stressmeter, 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 as the stressmeters are installed within concrete or
grout and somewhat isolated from potentially damaging electrical transients. However, there
may be occasions where some sort of lightning protection is desirable, for example where the
stressmeter is in contact with rebar that may be exposed to direct or indirect lightning strikes.
Also, 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 stressmeter and possibly destroy
it.
Note the following suggestions:
•
If the stressmeter 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 at the exit
point of the instrument cable from the structure being monitored. 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 gauge.
•
Plasma surge arrestors can be epoxy potted into the gauge cable close to the sensor. A ground
strap would connect the surge arrestor to earth ground, either a grounding stake or the rebar
itself.
Consult the factory for additional information on these or alternate lightning protection schemes.
Figure 5 - Lightning Protection Scheme