Ground Loops; Common Causes - Campbell CR300 Series Product Manual

3. In response, select the PakBus address of the remote data logger.
Once the Terminal master option is entered, the terminal will present a new prompt,
n*CR300>, where n is the remote CR300 series PakBus address.
4. Now, the remote device terminal functions can be accessed.

17.10 Ground loops

A ground loop is a condition in an electrical system that contains multiple conductive paths for
the flow of electrical current between two nodes. Multiple paths are usually associated with the
ground or 0 V-potential point of the circuit. Ground loops can result in signal noise,
communications errors, or a damaging flow of ground current on long cables. Most often,
ground loops do not have drastic negative effects and may be unavoidable. Special cases exist
where additional grounding helps shield noise from sensitive signals; however, in these cases,
multiple ground conductors are usually run tightly in parallel without conductive shielding
material placed between the parallel grounds. If possible, ground loops should be avoided.
When problems arise in a system, ground loops may be the source of the problems.
See also Grounds (p. 10).

17.10.1 Common causes

Some of the common causes of ground loops include the following:
The drain wire of a shielded cable is connected to the local ground at both ends, and the
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ground is already being carried by a conductor inside the cable. In this case, two wires, one
on either side of the cable shield, are connected to the ground nodes at both ends of the
cable.
A long cable connects the grounds of two electrical devices, and the mounting structure or
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grounding rod also directly connects the grounds of each device to the local earth ground.
The two paths, in this case, are the connecting cable and earth itself.
When electrical devices are connected to a common metal chassis such as an instrument
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tower, the structure can create a ground path in parallel to the ground wires in sensor
cables running over the structure.
Conductors connected to ground are found in most cables that connect to a data logger.
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These include sensors cables, communication cables, and power cables. Any time one of
these cables connects to the same two endpoints as another cable, a ground loop is
formed.
17. Tips and troubleshooting 133