When connecting multiple CPUs to a single transformer, it is
imperative that the polarity of the power supply terminals of
the CPUs and the polarity of the transformer always cor-
respond (namely: 24V-0 of the transformer must always be
connected to 24V-0 of the CPU, and 24V~ of the transformer
must always be connected with 24V~ of the CPU).
Depending upon the individual CPU, the numbering of the
corresponding two terminals may possibly deviate from the
norm (which is usually "terminal 1 = 24V-0" and "terminal 2 =
24V~"). In the following example, CPU 3 has a deviating
numbering and must be connected accordingly.
When using a single transformer for several CPUs,
each CPU ground must wired separately to the
If the field device transformer is physically far away
from the CPUs, earth grounding must still be
performed for the controller.
Use one star-point to split power for multiple CPUs
and field devices.
Connect earth ground to the proper terminal of the CPU.
NOISE-FREE EARTH GROUND
(ONLY ONE PER SYSTEM)
Fig. 48. Connecting and earthing multiple CPUs
EAGLEHAWK CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS