Lightning Protection - Campbell CR300 Series Operator's Manual

CR300-Series Datalogger

6.6.1 Lightning Protection

NOTE
38
In the field, at a minimum, a proper earth ground will consist of a 5-foot
copper-sheathed grounding rod driven into the earth and connected to the large
brass ground lug on the wiring panel with a 14 AWG wire. In low-conductive
substrates, such as sand, very dry soil, ice, or rock, a single ground rod will
probably not provide an adequate earth ground. For these situations, search for
published literature on lightning protection or contact a qualified lightning-
protection consultant.
In laboratory applications, locating a stable earth ground is challenging, but
still necessary. In older buildings, new Vac receptacles on older Vac wiring
may indicate that a safety ground exists when, in fact, the socket is not
grounded. If a safety ground does exist, good practice dictates the verification
that it carries no current. If the integrity of the Vac power ground is in doubt,
also ground the system through the building plumbing, or use another verified
connection to earth ground.
Lightning strikes may damage or destroy the CR300 and
associated sensors and power supplies.
The most common and destructive electrostatic discharges are primary and
secondary lightning strikes. Primary lightning strikes hit instrumentation
directly. Secondary strikes induce voltage in power lines or wires connected to
instrumentation. While elaborate, expensive, and nearly infallible lightning
protection systems are on the market, Campbell Scientific, for many years, has
employed a simple and inexpensive design that protects most systems in most
circumstances. The system employs a lightning rod, metal mast, heavy-gauge
ground wire, and ground rod to direct damaging current away from the CR300.
This system, however, not infallible. FIGURE
application of the system.
6-3 is a drawing of a typical