Stevens Water Monitoring Systems, Inc.

Grounding equipment can prevent costly repairs

Every remote environmental monitoring station should include a plan for an Earth Ground. All sensors, loggers and telemetry devices should be bonded, or connected, to the Earth Ground in order to protect instrument circuitry from damage due to changes in electric potential. Electric potential is defined as the difference in electrical energy between two points and is typically measured in volts and is more commonly referred to simply as voltage.

Assuming a ground is not needed when using a battery is often not enough because all of the paths of electric current, not just the power supply or battery, should be considered. Current will flow to ground through the path of least resistance. In a monitoring station without a good Earth Ground system, this path will most likely be through the system equipment.

For example, a water level sensor in contact with the water is one path to ground. During a storm, the station’s telemetry antenna can become charged – either through nearby lightning activity or simply highly charged clouds passing overhead. This charge can cause current to flow in the system. The current will flow to ground through the antenna cable to the radio, then through the data logger and finally to the water and the water level sensor. All of these devices may be subject to damage by the high current flow.

The Earth serves as a constant potential reference against which all other potentials can be measured. A ground system should have appropriate current carrying capacity in order to serve as an adequate zero-voltage reference. To establish a good Earth Ground, drive a grounding rod of at least four feet in length. To the grounding rod, connect solid heavy gauge grounding wire and run that to a copper grounding plate inside the system enclosure. Avoid any sharp bends greater than 45 degrees in the wire.

Inside the enclosure, connect all equipment grounds to the copper grounding plate. Do not “daisy-chain” one ground to another – each piece of equipment should have its own direct path to the plate with as short a path as possible and no sharp bends in the wires. If using bare ground wire, don’t let the wires touch or cross each other as this could cause ground loops.

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