A ground-loop in an electrical system, is an unwanted current that flows
in a conductor connecting two points that are nominally at the same
potential, i.e., ground, but are actually at different potentials [ground conductors have some other value than zero resistance]. For
example, the electrical potential at different points on the surface of
the Earth can vary by hundreds of volts, primarily from the influence of
the solar wind. Such an occurrence can be hazardous to personnel
working on long grounded conductors such as metallic telecommunications
cable pairs.
A ground loop can also exist in a floating ground system, i.e., one not
connected to an Earth ground, if the conductors that constitute the
ground system have a relatively high resistance, or have, flowing through
them, high currents that produce a significant voltage (IxR) drop. Ground
loops can be detrimental to the operation of the electrical system.
Contrast with ground current.
There are three fundamental grounding techniques;
1. Floating Ground System: The ground plane is not returned to
earth.
2. Single-Point Grounding System: A single
physical point in the circuitry is designated as a ground reference
point.
3. Multipoint Grounding System: The ground plane is taken to
earth, effectively taking each point connected to the ground plane to
earth.
Refer to MIL-HDBK-1857, Grounding, Bonding and Shielding Design Practices
A power plane at RF will act like a patch antenna, spreading spurious
signals all over the Printed wiring board.
An unintended antenna
connection.
Design Rules: |
How components are grounded in a circuit should always be taken into consideration to alleviate potential problems or enhance circuit operation. For example if the adjustment lead of a 3-terminal regulator is grounded near the load, than fluctuations in the load ground will be translated back to the the three-terminal regulator, in effect making the regulator's ground connection a sense line. Of course that only works if the load is located near the regulator.
PWB External Etched Copper Current Capacity Chart: current rating based on
trace cross section in square mils, temperature rise and current in
amperes.
Chart of
PWB Internal Etched Copper Current Capacity: current rating based on
trace cross section in square mils, temperature rise and current in
amperes.
Graphic of Minimum
Annular Ring, What is a Minimum Annular Ring.
Graph of PWB
Ground Potential, moving away from a single point ground connection
[example].
Electronic Chassis
Grounding
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