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3.4 Lightning Protection
In exposed locations, it is vital that the piezometer be protected against lightning strikes. A
tripolar plasma surge arrestor, which protects against voltage spikes across the input leads, is
built into the body of the piezometer. (See Figure 15.)
Additional lightning protection measures available include:
•
Placing a Lightning Arrestor Board (LAB-3) in line with the cable, as close as possible to
the installed piezometer. (See Figure 15.) These units utilize surge arrestors and
transzorbs to further protect the piezometer. This is the recommended method of
lightning protection.
•
Terminal boxes available from Geokon can be ordered with lightning protection built in.
The terminal board used to make the gage connections has provision for the installation
of plasma surge arrestors. Lightning Arrestor Boards (LAB-3) can also be incorporated
into the terminal box. The terminal box must be connected to an earth ground for these
levels of protection to be effective.
•
If the instruments will be read manually with a portable readout (no terminal box) a
simple way to help protect against lightning damage is to connect the cable leads to a
good earth ground when not in use. This will help shunt transients induced in the cable to
ground, away from the instrument.
Figure 15 - Recommended Lab-3 Lightning Protection Scheme
