Model 2000-SCAN Scanner Card User's Manual
Section 3: Operation
2000-SCAN-900-01 Rev. A / April 2018
3-19
Ground loops
When two or more instruments are connected, you must take precautions to avoid unwanted signals
from ground loops. Group loops typically occur when sensitive instrumentation is connected to other
instrumentation with more than one signal return path such as power line ground. As shown in the
following figure, the resulting ground loop causes current to flow through the instrumentation LO
signal leads and then back through the power line ground. This circulating current develops a small
but unwanted voltage between the LO terminals of the two instruments. This voltage will be added to
the source voltage, affecting the accuracy of the measurement.
Figure 26: Power line ground loops
