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DC Common
One of the DC Distribution Terminals should be designated as the "DC Common Point” (CP). There should be
only one DC Common Point per DC System. If the supply is to be used as a positive source, then the minus DC
Distribution Terminal is the DC Common Point; if it is to be a negative source, then the plus DT is the CP.
Here are some additional suggestions for selecting the best DC Common Point for five different classes of
loads:
a. Single Isolated Load--Select either the positive or negative DC Distribution Terminal as the DC Common
Point. A single isolated load exists when a power supply is connected to only one load, and that load circuit has
no internal connections to the chassis or ground. If the power supply output terminals are to be used as the DC
Distribution Terminals, then the DC Common point will be either the positive or negative power supply output
terminal (Figure 40A). On the other hand, if remote sensing is to be employed and the load terminals will serve
as the DT's, then either the positive or negative load terminal is designated as the CP (Figure 40B).
Figure 40. Preferred Ground Connections for Single Isolated Load
b. Multiple Ungrounded Loads--Select the positive or negative DC Distribution Terminal as the DC Common
Point. This alternative is applicable when there are two or more separate loads with separate pairs of load leads,
and none of the load circuits has internal connections to chassis or ground (Figure 41).