| In the electric world, the ground is a stable standard
which most instrumentation uses as a reference point. We sometimes
observe a spark between a hand and a doorknob which, isolated from
the ground, is charged with high potential. This much of high potential
could destroy semiconductors.
A stable system means that it is not isolated from the ground,
and that the power lines and signal lines are referenced to the
ground potential. However, a minute difference in the ground potentials
could cause an error in an instrumentation system handling several
volts as the full-scale.
It is common for the ground terminal of an instrumentation panel
to which many instruments are connected has a potential difference.
If a signal line is grounded at two points which have different
potentials, a current flow created by this difference is added to
the signal current.
Now if you have an isolator between these two instruments, each
ground point is galvanically separated. You can also choose any
grounding point ideal for each instrument (typically where it is
installed.) |
It
is said that the grounding at two locations would cause errors. Why? How
can I handle the problem?
When
you ground at two locations, you could create a ground loop through which
a current is transmitted from one instrument to another and added to the
signal. This problem can be solved by installing an isolator between them.
