It’s recommended to determine the soil type of the installation site and classify its
resistivity. The lower the resistivity, the better the earth grounding must be. Soil
resistivity depends to soil moisture and temperature (low temperatures mean higher
resistivity).
The industry standards for grounding are often out of the budget and scope of the met
mast for WRA as the cost of adding salt soils, measuring resistivity, etc., would
significantly increase the cost for a temporary installation. The purpose of this chapter
is to explain the basics of grounding and lightning protection, without going into the
subject in depth.
The first element of a met mast grounding system is the lightning rod: a copper-clad
lightning spike (sometimes a metal spike covered with wolfram to resist the heat of the
strike). The spike is to be installed on top of the structure, above sensors installed there.
The lightning rod gives effective protection to all elements located inside a 45º degrees
cone underneath it.
To join the lightning rod to the grounding rod we recommend using at least a 35mm
2
copper ground wire. Grounding rods are usually 1,5m long.
To ground the Orbit 360 data logger, connect one end of the copper ground wire (usually
yellow-green color) to the data logger GND terminal (orange plug) and the other end to
an independent grounding spike. If the enclosure is metallic you must also connect the
enclosure to the ground wire of the data logger, to do so, all metallic enclosures have a
connection screw terminal with the ground symbol on it.
Shielded wires must be used for all sensors, the shield helps to minimize
electromagnetic interference and provides additional mechanical resistance. If you are
installing a considerable amount of sensors it is recommended to connect all shields in
an external patch panel and then use a single wire to connect the patch panel to the
logger GND terminal.
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